GeoLog Blog

Energy tradeoffs

2010-10-22T05:16:00.004-04:00

There is no one easy solution to meeting the energy needs of the 21^st century and beyond; every technology has its trade-offs:

Petroleum and coal are both non-renewable and produce greenhouse gases; solar and wind energy both require lots of land and the energy collected from them can not yet be efficiently distributed; and hazardous waste from nuclear power plants must be dealt with for thousands of years.

Less obvious are the hidden costs of energy sources; biofuels, regarded as the “greenest” technology, uses hundred of liters of water to grow the fuel.

The other side of the energy equation is reducing use, which is an issue that involves education and public policy. The solution to our future energy needs requires the input from scientists, engineers, educators, policy makers, and you.

Science magazine has a special section on scaling up alternative energies and the trade-offs involved.

[Adrian Cho, Science, v. 329, 13 August 2010,p. 786-787]

Image from here.

Geothermal energy, revisited

2010-10-21T06:01:00.002-04:00

Volcanoes and geysers bear witness to the enormous reservoir of energy--in the form of heat--that lies in the earth's interior. This geothermal energy can be used to generate electricity wherever there is a source of heat close to the earth's surface. Unlike the non-renewable fossil fuels, geothermal energy will last until the earth's internal engine runs out of fuel, millions of years from now.

But geothermal energy has its limitations as an alternative energy source. Production of geothermal energy is limited to relatively few areas with the required local geothermal source, and drilling to tap these sources can have unintended consequences. A geothermal project in Switzerland was canceled in 2007 after drilling caused a magnitude 3.4 earth tremor.

Source: E. Kintisch, Science 329:789, 13 Aug. 2010

Photo from here, along with a list of "Top 10 alternative energy sources"

Ethanol and policy issues

2010-10-20T06:01:00.004-04:00

Recently, the U.S. government increased the cap on the amount of ethanol that can be used in gasoline from 10% to 15%. Upping this limit should encourage the development of alternative sources of ethanol, but changing this limit affects the car manufacturers.

A proposal to require cars to use an E85 blend (that is, 85% ethanol, 15 % petroleum) could be accommodated by car manufacturers, but it is not known whether this ethanol-rich blend would damage engines designed to operate on the current 10% blend.

Scaling up the use of cellulosic biofuel is not just a scientific or technological issue, but a policy issue as well. One scenario would be to have the ethanol limit gradually increase from to 85%; the current increase to 15% is a down payment on this strategy.

Learn more about E85 and "flex fuel" vehicles here.

Photo: an E85-powered Chevrolet HHR.

Growing Green

2010-10-19T08:08:00.003-04:00

A major roadblock to scaling up the use of cellulosic biofuel is the difficulty and expense of extracting the ethanol from these materials.

The ethanol currently used in gasoline mixtures come from fermentation of sugars present in corn kernels, and is a relatively simple and inexpensive process. However, the sugar in cornstalks and other cellulosic biofuel is locked in chemical structures that are harder to break and the ethanol yield is lower, which means that manufacturers of cellulosic ethanol require much more raw material than the ethanol manufacturers.

Scientists are exploring ways to extract cellulosic ethanol more effectively. One possible solution is to engineer new microbes that can break down cellulose into sugars that can more easily be fermented to form ethanol.

The Great Lakes Bioenergy Research Center is a consortium of organizations working to conduct this sort of "transformational biofuels research". Go Green!

Biofuels

2010-10-18T09:57:00.003-04:00

Ethanol is a fuel derived from plant material, primarily corn kernels. Although a renewable resource, one of the down-sides of using corn-derived ethanol as fuel is that it diverts grain from food to energy use, driving up food prices. This concern was addressed by research into using biowaste, that is, grasses, cornstalks, and wood chips not used for food.

The problem with using this “cellulosic” ethanol is that the ethanol is much harder to extract. Currently, just 40% of the energy content available in cellulosic plant sources is recoverable, compared to 90% of the energy in kernal ethanol.

But another issue with ethanol from corn is that the process requires a lot of energy, and the end-product ethanol does not represent a big savings in the use of fossil fuels in the process and still contributes to greenhouse gas emissions.

More on the pros and cons of ethanol, here.

Wind energy, revisited

2010-10-15T08:40:00.002-04:00

Wind..it’s clean, and does not produce climate-changing greenhouse gasses...

But problems associated with modern wind turbines threaten the growth of wind as an alternative energy source. Birds and bats have been killed by the spinning blades, the motion of the blades can show up on flight controller’s radar, and noise is an issue for people who live near wind turbines.

Twenty years of using modern wind technology has led to some improvements; siting wind turbines now takes into account migratory routes and roosting sites of birds and bats. Engineers are working to make the turbine blades less visible to radar and less noisy.

Ultimately, however, changing negative attitudes toward wind farms must involve more than technological fixes and include public education of the benefits and tradeoffs of wind energy technology.

Source: E. Kintisch, Science 329:788-789

Nuclear power, revisited

2010-10-14T08:50:00.002-04:00

Nuclear energy became anathema after nuclear plant accidents released radioactivity into the environment. But in the wake of environmental accidents due to oil spills and growing concerns about the environmental impact of burning coal, nuclear power is making a comeback.

More than 100 new nuclear power plants are planned to come online, worldwide, over the next 10 years. Lessons learned since Three-Mile Island insure that the new reactors will be safer.

Still a challenge to acceptance and wide-spread use of nuclear power is the disposal of high-level nuclear wastes (HLW), especially the spent fuel rods, which may continue to emit dangerous levels of radiation for a million years. Disposal of HLW is not just a scientific issue but a political hot potato.

Image of the atom from here.

National Fossil Day

2010-10-13T08:23:00.003-04:00

The record of life on Earth is written in stone--

National Fossil Day is a celebration organized by the National Park Service to promote public awareness and stewardship of fossils, as well as to foster a greater appreciation of their scientific and educational values.

Learn more...

2010-10-12T06:04:00.004-04:00

Solar power has matured as an alternative energy source over the last 20 years, but there are still obstacles to overcome before the energy from the sun can significantly supplement other sources of energy.

Collecting solar energy is only part of the process, storing it for later use is still “technically and economically challenging.”* Concentrating solar power plants, or CSPs, like the one shown here, use mirrors to focus solar radiation and generate heat that can be converted to energy, but CSPs are located where the solar radiation is most abundant year-round, which is not where most people and most of the energy demand is.

There are environmental issues, as well. Recently the California Energy Commission recommend against building a new installation in the Mohave desert because of its potential impact on turtles.

*Source: Science, 329:773, August 13, 2010, Roeb, M, and H. Muller-Steinhagen

Photo of concentrated solar power plant, and other information on solar power is available here. This structure's resemblance to Isengard is interesting...

It's Earth Science Week

2010-10-11T08:18:00.005-04:00

If you are under the age of 30, you may not be aware that the term “energy crisis” was NOT coined during your lifetime. Your parents might remember the lines at gas stations in the late 1970s.

We find ourselves in the 21^st century apparently not having learned the lessons from our earlier crises that stemmed from dependence on a non-renewable energy source—petroleum—the production and transportation of which can have profound environmental effects (two examples: Exxon Valdez and the Deep Horizon oil rig) and the combustion of which contributes to global climate change.

We have learned that our energy choices have profound geopolitical, social, and environmental consequences. The American Geological Institute designates a week in October as Earth Science Week, and this year's theme is energy.

AGI's webpage for Earth Science week is here.

Flower Power

2010-10-07T08:37:00.003-04:00

What would a world without flowers be like?

The dinosaurs knew the answer to that question, as they lived in an age before the evolution of angiosperms, the flowering plants.

Angiosperms are the most diverse group of land plants on Earth today, and include not only all the plants whose blooms we appreciate, like roses, but all our deciduous trees and grasses, and grains--corn, rice, and wheat.

Paleontologists have modeled the flower-less Earth scenario, and found that an Earth without flowers would not only be less colorful, but it would be hotter and drier, as the leaves from angiosperms add a significant amount of water vapor to the atmosphere through the process of transpiration.

Moisture impacts biodiversity as well, and a flower-less Earth would have fewer species of plants and animals. Angiosperms add more than just color to our lives

More information on a world without angiosperms, and a link to the original research here.

Melville's Whale

2010-10-06T09:24:00.003-04:00

Modern sperm whales, the largest predators alive today, have teeth only on the lower jaw and use suction to catch their cephalopod prey.

The discovery of a new fossil species of sperm whale from rocks 15 million years old helps to fill in our understanding of the evolution of sperm whales. The newly discovered whale has jaws that have both upper and lower teeth, teeth that are 36 cm long, giving this fossil predator the biggest bite known. Based on the size of the skull, paleontologists estimate a body length of 13 to 17 meters.

Named Leviathan melvillei, for the novelist Herman Melville, author of Moby Dick, this sperm whale's appearance in the fossil record coincides with diversification of baleen whales. Leviathan melvillei probably fed on baleen whales and as a top predator, helped shape Miocene marine communities.

See summary of the Nature article and more illustrations here.

Warm-blooded reptiles?

2010-10-05T08:39:00.002-04:00

Modern reptiles are cold blooded, but what about extinct reptiles?

Based on their teeth, large extinct swimming reptiles, like ichthyosaurs, plesiosaurs, and mosasaurs are thought to have been predators in the Mesozoic oceans. Their streamlined body profile also suggests an active lifestyle. An active lifestyle requires high metabolic rates, which are usually correlated with at least some ability to regulate body temperature.

Scientists analyzed oxygen isotopes from the teeth of these extinct marine reptiles and compared the values with those from cold-blooded fossil fish. The results showed ichthyosaurs and plesiosaurs differed significantly from fish, and suggest that these two reptiles, both of whom were active, pursuit predators, probably controlled their body temperature. The data for mosasaurs were equivocal and suggest that mosasaurs led a different lifestyle perhaps as an opportunistic ambush predator.

Illustration of an ichthyosaur is from here.

The fauna that keeps on giving

2010-10-04T06:01:00.003-04:00

The Burgess Shale of British Columbia, Canada, is famous for its exceptional preservation of bizarre, soft-bodied invertebrate lifeforms, a window into the Middle Cambrian World of 510 million years ago.

Burgess Shale-like faunas are now known from localities world-wide, but recently paleontologists discovered in Morocco a Burgess fauna from rocks 30 million years younger than the Cambrian faunas.

Burgess shale faunas were thought to have gone extinct after the Middle Cambrian. This new discovery suggests that the disappearance of the older fauna was a due to the absence of suitable conditions for fossilization rather than extinction, and it underlines the importance of understanding the conditions and processes leading to fossilization, and it opens the possibility of finding other Burgess faunas.

From P. Van Roy, P. J. Orr, J. P. Botting, L. A. Muir, Jacob Vinther, B. Lefebvre, K. el Hariri, and D. E. G. Briggs. 2010. Ordovician faunas of Burgess Shale type. Nature 465:215-218. A longer summary of their research is here. Photo of Marella, a Burgess arthropod, from the original article.

Steno and stratigraphy

2010-09-30T11:35:00.000-04:00

Nicholas Steno, born in 1638, was a renaissance era scholar, whose experience in comparative anatomy provided some of the earliest evidence recognizing fossils as the preserved remains of animals, which he famously demonstrated by comparing modern shark teeth to fossils shark teeth.

Steno is also credited with enunciating basic principles of geology that help determine the relative order of geological events that led to the development of a geological time scale.

Steno reasoned that sedimentary rock layers were formed when particles in a fluid such as water fell to the bottom, resulting in horizontal layers. Thus Steno's principle of original horizontality states that these rock layers form in the horizontal position.

Steno realized that tilted or folded rock layers, like the ones shown in the illustration here, meant that the layers were disturbed after they were deposited. It may seem obvious to us today, but this insight represented a huge step toward understanding 4.6 billion years of earth history.

Image and more information available here.

Telling time with sedimentary rock layers

2010-09-29T14:30:00.000-04:00

Nicholas Steno is also credited with being the first to understand (and communicate to others) the most basic principle of ordering sedimentary strata, the principle of superposition, which states that in a sequence of undeformed rock strata, the oldest beds are on the bottom and the youngest are on the top. Simple, yes?

It is important to remember that this principle refers specifically to sedimentary rocks, deposited layer by layer as strata. Some metamorphic rocks may show banding that resembles layering (compare the layered gneiss show above to the sandstone), but these “layers” do not follow the principle of superposition—they reflect reorganization of grains due to stresses in the Earth’s crust associated with plate tectonics. It is sometimes difficult for aspiring geologists to tell the difference, especially in an isolated hand-sample. Familiarity with the three main types of rocks is the key to making this distinction.

The diagram, above (from here), shows how the process of superposition could happen in a lake setting.

Finding order among the rocks

2010-09-28T08:30:00.003-04:00

When geologists refer to events that occurred 200 million years ago, they are referring to dates on the geological time scale that have been added since the discovery in the late 19^th century of the use of radioactive decay as a tool for determining the age of geologic materials.

The geological time scale is an evolving document, and radiometric dates are subject to refinement as technology advances.

But the geological time scale has always been an evolving document, even before dates were added. The names of the geologic eras, periods, and epochs on the geologic time scale we use today were not written in stone (so to speak!) but represent the latest version of a document that has its origins in principles enunciated almost 400 years ago.

Figuring out the order in which rock layers were deposited or emplaced was the first step to developing a time scale.

What is time?

2010-09-27T08:00:00.000-04:00

How can geologists use rocks to create a chronology of Earth history?

To address this issue we need to understand the basic measure of time.

The orbit of the Earth around the Sun measures a year, the rotation of the Earth on its axis defines a day, and the vibration of the Cesium atom in an observatory near London marks seconds, but what do these different phenomena have in common?

A year is measured by the change in the position of the Earth in its orbit relative to the sun; a day is measured by change due to Earth’s rotation, and a second is measured by the change in position of a vibrating atom. Change is the fundamental measure of time.

Changes are recorded in rocks, for example, the layers of sedimentary rock record periods of deposition alternating with periods of non-deposition; metamorphic rocks record change from a previous non-metamorphosed state, igneous rocks record the change of cooling from a molten state to a crystalline state. So it’s valid to use rocks as geochronometers in sorting out the history of the Earth.

The "spiral of time" graphic (a classic!) can be found here, along with more information.

Stories pebbles tell

2010-09-07T12:10:00.004-04:00

From their first discovery, fossils had been interpreted as stones that fell from the sky, tricks of the devil, or objects that grew in the rocks in which they are found.

Nicholas Steno’s work with modern shark teeth convinced him that the objects we recognize as fossil shark teeth looked like shark teeth because they were shark teeth, and that they must have been buried in mud or that was now dry land.

Steno also reasoned that if the fossil were a structure that had grown within solid rock, its shape would have been distorted by the enclosing rock. The pristine condition of the fossil shark teeth indicated instead that the tooth must have been buried in soft sediments which hardened later.

Steno’s realization that objects entombed within rock, like fossils or pebbles in a conglomerate were formed before the rock itself was deposited. This was another way to distinguish the relative order of events and is called the principle of included fragments.

Simply put, this principle states that the included fragment (be it a fossil in limestone or a rounded pebble in a conglomerate, shown above) is older than the rock that encloses it.

Image and more information available here.

Hawaii and the future

2010-08-12T08:00:00.000-04:00

The submersed, volcanically inactive islands of the northwest part of the volcanic archipelago of volcanic islands of which the state of Hawai'i is a part, points to the future of the present Hawaiian islands.

As the Pacific Plate continues its cm-by-cm journey to the northwest, the Big Island of Hawai'i will move off the hot spot, its volcanic activity will cease, and erosion will eventually reduce the island to a submersed shadow of its former self.

This rather bleak view of Hawai'i’s future is tempered with the knowledge that even as erosion claims the older islands, and eventually the big island, even now the next island in the chain is growing on the seafloor off the southeast coast of Hawaii. Loihi is the name already given to this next piece of real estate in the Hawaiian chain.

Image of Loihi from here.

Hawaii and hot spots

2010-08-11T20:00:00.001-04:00

The Hawai'i archipelago is the product of the interplay of plate tectonics—the shifting of the Earth’s outer, rigid crust—with a plume of molten material welling up from the Earth’s mantle, a hotspot.

The Hawaiian islands formed sequentially as the Pacific plate moved to the northwest over this hotspot. The upwelling magma erupted as basaltic flows on the ocean floor that eventually built up thousands of feet to breach the surface and form an island.

As the Pacific plate continued its movement to the northwest, the new island moved off the hot spot, and volcanic activity ceased. Once volcanic activity ceased, no new rock was added to the island, and surface processes, the action of wind and waves, became the dominant processes in shaping the island, and the quieted volcanic island began to succumb to erosion, eventually disappearing beneath the waves.

Photo: the southern coast of the Big Island takes a pounding from the waves.

More Aloha

2010-08-10T15:42:00.001-04:00

The islands that comprise the state of Hawai’i are part of an extensive archipelago of volcanic islands—most of them well below sea level and most of them dormant---that stretches from the Big Island of Hawaii north and west to the Aleution Islands, another volcanic archipelago that stretches westward from Alaska to Asia.

Radiometric dates of basalts show that Hawaii’s islands grow older to the northwest; the big Island, the southernmost island in the chain, is the youngest (and indeed is still growing through active volcanic flows).

The Big Island is also the largest of the islands, thus it’s name, and the older islands are smaller.

The Big Island is the only currently volcanically active island; the older islands are not.

These three different lines of observation led geologists to formulate the hot spot theory.

Illustration from here.

Hawai’i Volcanoes National Park

2010-08-09T08:00:00.001-04:00

Most national parks and monuments preserve the story of the park’s geological past—past climates, past tectonic history. At Hawai’i Volcanoes National Park on the Big Island of Hawai’i, Hawai’i’s past, present, and future is written in basalt—the cooled basalt that comprises the island and the still-molten basalt flows that snake their way to the ocean on the islands’ south-east shore.

The Big Island of Hawai'i is the southernmost island in the archipelago that comprises the islands in the state of Hawaii but that extends northwestward as a submersed chain of seamounts to the Aleutian archipelago of Alaska. The Big Island of Hawaii is the largest island and the only one in the chain still volcanically active.

See Google maps image to trace the Hawaiian island chain.

The US Geological Survey maintains the best site for Hawaiian volcanic activity.

Photo: night viewing of active basalt flows, Kilauea volcano on the Big Island.

Hawai'i on a budget

2010-08-07T15:57:00.002-04:00

If you can’t make it to Hawaii to see the effects of basaltic volcanism you might plan a visit to Craters of the Moon National Monument in Central Idaho.

The barren landscape that gives the name to the area is the result of volcanic activity 15,000-2000 years ago, and was shaped by forces similar to those that shaped the Hawaiian islands.

Craters of the Moon is a part of what is called the Great Rift volcanic zone, a 50-mile-long corridor encompassing an area roughly the size of the state of Rhode Island. The area includes 60 lava flows and 25 volcanic cones.

A rift zone is an area where the Earth’s crust is being pulled apart, allowing magma to well up from below. The cause of the rifting is still a matter of study, but, as with the basalt eruptions of Hawaii, the cause may be a hot spot in the mantle beneath the North American continent.

P.S. In 1969 Apollo 14 astronauts Alan Shepard, Edgar Mitchell, Joe Engle and Eugene Cernan visited Craters of the Moon. They explored the lava landscape in order to learn the basics of volcanic geology in preparation for future trips to the moon.

P.P.S. “The Devil's Vomit" is how one pioneer described Craters of the Moon. In the 1850's and 1860's hundreds of pioneers traveled through the area along the Oregon trail.

Photo from the National Parks Service

Oregon's trail through time

2010-08-06T16:09:00.002-04:00

In North-Central Oregon, the John Day Fossil Beds record a succession of ecosystems over 57 million years from lush tropical jungle with crocodiles and palm trees to cooler and drier forests and grassland inhabited by horses and camels.

The dramatically shifting landscape evolved as tectonic plate collision along the nearby North American plate boundary gave rise to volcanic mountains along the west coast.

Some of the sedimentary layers at John Day are the deposits of massive mudflows generated by volcanic eruptions that engulfed entire forests. Other beds resemble those at Florissant in Wyoming—fossil lake deposits preserving fish, leaves, and insects.

Like Idaho’s Hagerman fossil beds, the youngest John Day beds preserve a pre-ice-age fauna, and the painted hills of the John Day beds recall the deeply weathered deposits of South Dakota’s Badlands.

Learn more about the John Day fossil beds here.

Illustration of the stratigraphic sequence is from here.

http://www.nps.gov/joda/naturescience/geologicformations.htm

Idaho's fossil horse

2010-08-05T08:21:00.004-04:00

In an area of south-central Idaho, bounded on the east by the Snake River and on the south by the Oregon trail, the 3-4 million year old sedimentary rocks of the Hagerman fossil beds preserve the largest concentrations of fossil horses in North America, in addition to over 200 species of plants and animals, including bear, otter, camel, sabertooth cat, and even a mole.

These rocks preserve a slice of time before the last Ice Age. Today, the area receives less than 10 inches of rainfall; the fossils give evidence that the climate in which these animals lived was much wetter.

The site is named for a species of fossil horse, Equus simplicidens, found in abundance near Hagerman, Idaho. It is the state fossil of Idaho, and the oldest known example Equus, the genus that includes modern horses, donkeys, and zebras.

P.S. The Hagerman horse was chosen for the theme of the "Idaho" U-Haul graphic.

More information on the Hagerman Fossil Beds here.

The illustration is an artist's reconstruction of the Hagerman ecosystem during the Pliocene Epoch. The original painting is at the Smithsonian Institution.

Colorado’s fossil redwood forest

2010-08-04T09:37:00.003-04:00

34 million years ago, in central Colorado, volcanic eruptions sent mudflows downslope, burying a forest of giant redwoods, damming a nearby river, and forming a large lake.

Subsequent eruptions deposited volcanic ash that buried insects and plants washed into the lake. The fine-grained ash preserved the smallest detail, including the antennae, legs, and sensory hairs of insects and the petals of flowers. This story is preserved in the rocks of Florissant Fossil Beds National Monument.

Florissant is famous for its abundance of fossil leaves, large tree stumps, and insects. More than 1,500 different kinds of fossil insects are found here, including dragonflies, cockroaches, grasshoppers, flies, beetles, wasps, ants and butterflies. The largest fossil tree preserved at Florissant is 13 feet in diameter and estimated to have been 300 feet tall and 1,000 years old.

A fossil photo gallery can be found here.

The image, above is from here.

Wyoming's fossil lake

2010-08-03T08:35:00.002-04:00

50 million years ago, during the Eocene Epoch of the Cenozoic Era, a sub-tropical lake covered a portion of what is now southwestern Wyoming.

Fossil Butte National Monument preserves in its finely layered sedimentary rocks a window into the aquatic and nearby terrestrial ecosystems of this time. The deposits are famous for the diversity and abundance of its fossil fish, and other fossils include reptiles, birds, insects, plants, and the oldest known fossil bat.

Preservation of these fossils is exquisite, suggesting that conditions at the bottom of the lake were toxic, and excluded the scavengers and decomposers that otherwise would have destroyed these remains.

Workers building the Union Pacific railroad in the late 1860’s discovered the fossil fish beds near the town of Green River, Wyoming, and geologists refer to these fossil-bearing strata as the Green River Formation.

More information from the National Parks Service, here.

http://www.nps.gov/fobu/naturescience/naturalfeaturesandecosystems.htm

Dinosaur National Monument

2010-08-02T08:13:00.002-04:00

In 1909 Earl Douglass, a vertebrate paleontologist from the Carnegie Museum of Pittsburgh, Pennsylvania, mounted an expedition to northeastern Utah to prospect for dinosaurs for his Museum.

Douglass chose his prospecting site carefully, knowing that dinosaurs were likely to be found in the preserved sediments of ancient river systems. The expedition was a resounding success, and in 1915 President Woodrow Wilson proclaimed the Douglass quarry Dinosaur National Monument.

The Monument preserves the remains of more than 1500 fossil bones in place in the sandstone in which they were preserved. Thanks to tectonics, the originally flat-lying sedimentary rock layers were tilted upwards so that the fossil bone bed forms a wall of the visitor’s center, a kind of paleontological bas relief.

More information from the National Parks Service here.

White Sands

2010-07-30T09:53:00.002-04:00

To most people the word sand means the stuff that beaches and deserts are covered with and to many of us that means sand-sized grains of the mineral quartz, the most resistant mineral at the Earth’s surface.

Quartz is insoluble and slow to weather, and so it is the stuff of many deserts and beaches. However, in a desert where the little water that falls every year creates temporary lakes, as those lakes evaporate, the minerals dissolved in the water precipitate, forming crystals of evaporite minerals like salt and gypsum.

As the winds whip across these dried up lakebeds, the crystals are swept up and piled into great glistening dunes of white gypsum sand. This is White Sands National Monument in New Mexico.

Photo from here.

More info on the park here.

Carlsbad Caverns

2010-07-29T07:26:00.007-04:00

The desert that surrounds Carlsbad Caverns National Park in southeastern New Mexico is not an environment conducive to cave formation and cannot account for the over 100 caves dissolved from the areas’ limestone bedrock; most of the cave formation in this area took place during the last ice age when the climate here was wetter and pine forests covered the landscape above the cave.

Unlike Mammoth Cave, which was formed by slightly acidic groundwater percolating down from the surface dissolving and enlarging fractures, at Carlsbad Caverns water enriched with hydrogen-sulfide from oil and gas deposits buried in sedimentary layers beneath the limestone migrated up from below and mixed with rainwater to form sulfuric acid, dissolving the rock and but leaving behind delicate cave deposits made of gypsum.

More information on Carlsbad from the National Parks Service.

http://www.nps.gov/cave/naturescience/cave.htm

2010-07-28T15:08:00.002-04:00

Beneath the rolling hills of south-central Kentucky, subterranean chambers coalesce over 400 square miles to form the largest cave system in the world, the aptly named Mammoth Cave.

The vastness of Mammoth Cave belies its formation by literally one drop of water at a time.

Groundwater percolating through the fractured limestone bedrock dissolves the rock a molecule at a time, slowly enlarging the fractures.

Once a cave is formed, as mineral-laden groundwater drips down from the roof of the cave, crystals of calcium carbonate precipitate out and adhere to the cave roof—the beginning of a stalactite, icicle-like formations that hold tight to the ceiling. On the cave floor beneath the dripping water, calcium carbonate crystals may accumulate in a stalagmite; remember it just might reach the cave roof.

More info on Mammoth Cave National park here.

Photo from here.

Petrified Forest

2010-07-27T08:12:00.003-04:00

Standing in the blazing sun of the eastern Arizona desert, you would not suspect that 200 million years ago towering sequoias nearly 200 feet tall and 9 feet in diameter grew here in lush forests among broad rivers.

The evidence of this vanished ecosystem, of course, lies scattered on the ground—the fossilized trunks of these trees that give the name to Petrified Forest National Park.

Over the millennia, climates changed, shallow seas covered the region, depositing marine sediments and burying the fossil forest deeper until about 60 million years ago when tectonic forces pushed upward the entire area we call the Colorado Plateau. Erosion followed, stripping off the younger sedimentary layers and eventually bringing the fossil forest to once more to light.

More information here.

http://www.nps.gov/pefo/naturescience/fossils.htm

P.S., In addition to the plants, this Late Triassic ecosystem supported insects, amphibians, and reptiles, including crocodile-like phytosaurs and Coelophysis, an early dinosaur.

When the Badlands weren't bad

2010-07-26T09:35:00.003-04:00

Early visitors to the southwest corner of South Dakota gave the name badlands to the area, as the arid, desolate, deeply eroded landscape could not support agriculture or even grazing livestock.

But 40 million years ago Badlands National Park was a very different place, where lush vegetation supported an abundance of grazing animals.

The Badlands are famous for its many fossil mammals, including Ancestral horses and camels, sheep-like oredonts and rhinoceros-like brontotheres.

About 5 million years ago the picture started to change, as tectonic forces caused uplift and facilitated erosion of the soft sedimentary rocks, creating the spectacular stark scenery which the park is known for today.

For more information, click here.

Photo is from Wikipedia Commons.

Devils Tower (a.k.a. Bear's Lodge)

2010-07-23T08:07:00.003-04:00

Rising out of the plains of northeastern Wyoming, Devils Tower looms 867’ over low rolling hills of shale and sandstone.

The tower itself is composed of much harder igneous rock. Large crystals in the rock indicate slow cooling of magma, and give us clues to the Tower’s origin deep beneath the present-day land surface.

The sandstones and shales that surround Devils Tower were deposited in a shallow sea that covered western North America 225 million years ago. Long after the seas drained away and the sand and mud hardened into sandstone and shale tectonic forces drove magma upward.

Millenia of erosion stripped away the surrounding sandstone and shale, gradually revealing what was designated in 1906 as North America’s first national monument.

More information here. Photo by the author.

Mt. Rushmore & the Black Hills of South Dakota

2010-07-22T19:44:00.003-04:00

As with Yosemite and Acadia, the geologic story of Mt. Rushmore comprises two chapters: the origin of the rock and how those rocks became exposed at the Earth’s surface.

About 1.6 billion years ago magma from the mantle made its way upwards through the crust and cooled deep below the surface forming the granite that is the core of the Black Hills.

The granite lay buried until about 70 million years ago when tectonic forces within the Earth caused the Black Hills region to rise.

Erosion stripped off less resistant sedimentary rocks, and as uplift continued the harder igneous rock was exposed at the surface. In an area of the Black Hills called the Needles, vertical joints in the granite resulted in the formation of thin granite spires (see photo).

And in a large block of unjointed granite, sculptor Gutzon Borglum carved his iconic tribute to 4 U.S. presidents.

More information here.

A tale of two parks

2010-07-21T08:13:00.003-04:00

Like California’s Yosemite National Park, the predominant rock type in Acadia National Park in Maine is granite.

Acadia is geologically older; the granites of Acadia originated in the core of ancient mountains that formed from the collision of a micro-continent with eastern North America about 450 million years ago.

But both parks experienced glaciation in the last 2 million years. In both areas, glaciers polished the granite, carved U-shaped valleys, and deposited ridges of rock, sand, and gravel called moraines. In Yosemite, these Alpine glaciers originated at high elevations and flowed down pre-existing valleys. In Acadia continental ice sheets more than a mile thick originated in Canada and slowly flowed across the entire landscape. Acadia’s glaciers are long gone, but like Yosemite its landscape continues to evolve.

For more on Acadia, click here.

The other half of Yosemite's story

2010-07-20T08:03:00.002-04:00

Although Half Dome formed deep within the Earth, near-surface processes are responsible for the Dome’s familiar profile.

The steep vertical face of Half Dome formed from vertical cracks, called joints,that developed in response to tectonic stresses in the Earth’s crust.

The spherical side is a result of exfoliation, a weathering phenomenon in which thin, concentric sheets of rock spall off the exposed surface.

Both phenomena are the result of the uplift of the granite pluton, erosion of the overlying rock layers and the accompanying release of pressure as this overburden was removed.

Ice-age glaciers flowed down the valley, clearing away the weathered debris, but the glaciers themselves did not carve out Half Dome, they just accentuated what had already been given shape by weathering.

Photo: spheroidal surface developed on granite at Yosemite

Half of the Yosemite story

2010-07-19T08:00:00.001-04:00

For many visitors, the dramatic profile of Half Dome stands as the symbol of Yosemite National Park in northern California.

Half Dome is composed of granite, an igneous rock that forms deep within the Earth’s crust by intrusion of molten magma from below.

But how does a rock that is formed deep within the Earth’s crust come to tower over the modern landscape?

Long after the magma cooled to form large granite bodies, called plutons, tectonic forces pushed the area upwards. As the region was uplifted, erosion stripped away the less-resistant layers of rock overlying the granite plutons, eventually leaving the granite exposed to dominate the landscape.

Uplift and erosion are still active in the area today, and Yosemite’s landscape continues to evolve.

Photo of Half Dome is from here.

The more recent history of the Grand Canyon

2010-07-16T08:09:00.003-04:00

The rocks exposed in the Grand Canyon record 2 billion years of Earth history, but the canyon itself is much younger.

Until recently most geologists estimated that the canyon formed 5 to 7 million years ago, based on radiometric dates on lava flows in the canyon.

Recently researchers from the University of New Mexico reported radiometric dates on cave deposits in the western part of the Canyon that indicated an age of 17 million years. These cave deposits are known to form near the water table. The water table dropped as the canyon carved its way downward, and caves formed early in the canyon’s history lie higher in the canyon’s walls than later-formed caves and have older deposits than caves lower in the canyon.

The new study should stimulate more research on piecing together the story of the canyon’s formation.

Source: Polyak, V., Hil, C., and Asmerom, Y., 2008. Age and evolution of the Grand Canyone revealed by U-Pb dating of water table-type speleothems. Science 319 no. 5868 p. 1377-1380. Free registration at the AAAS/Science website permits access to this article.

Or see this nice summary with great color photos (including the cave deposits shown above).

Grand Canyon: 2 billion years of Earth history, one step at a time

2010-07-15T07:51:00.003-04:00

Nearly half of Earth’s history is exposed in the walls of the Grand Canyon in northern Arizona, USA.

Grand Canyon National Park is a natural geology textbook, and each layer of rock or stratum is a page of that history. To hike down the canyon is to walk back into time. The rocks of the upper canyon are relatively soft, flat-lying sedimentary rocks—limestone, sandstone, and shale deposited in ancient shallow seas, beaches, and swamps.

Erosion by the Colorado River and gravity-powered mass wasting have combined to create an upper gorge that is up to 18 miles across. At river level, 2 billion-year-old igneous and metamorphic rocks of the narrow inner gorge mark the remnants of ancient mountains.

Photo from here.

Yellowstone: Life in Hard Places

2010-07-14T08:34:00.004-04:00

The geysers, mud pots, fumaroles and thermal springs that attract millions of visitors to Yellowstone National Park every year also attract a growing number of scientists.

The brilliant yellow, orange and red hues that tinge some of the hot springs are microbes that live in these boiling hot environments. Organisms that are adapted to live under extreme conditions of heat, cold, pressure, depth or chemical environment are called extremophiles.

Scientists are interested in studying extremophiles because these organisms live in conditions that are known to exist on other planets, so our search for understanding the life forms we might find on Mars can begin in our own backyard.

For more on extremophiles in Yellowstone and elsewhere, click here.

Photo of Old Faithful by the author.

Yellowstone

2010-07-13T08:05:00.002-04:00

Yellowstone National Park, centered in the northwest corner of Wyoming, was America’s first national park, established in 1872, but the story of Yellowstone’s current landscape starts just over 2 million years ago with a series of terrific volcanic eruptions that triggered the collapse of the volcanoes and formation of calderas—large, basin-like depressions.

Yellowstone Lake occupies the youngest caldera that formed in the last big eruption about 600,000 years ago. The volcanic activity and geothermal features in Yellowstone are attributed to the presence of a hot spot, or upwelling of hot mantle material deep below the park, and as long as that subterranean heat source lasts, Yellowstone’s landscape will continue to evolve.

Photo: Yellowstone geyser. Photo by the author.

Geology of Vacation Destinations

2010-07-12T07:43:00.003-04:00

It’s summer, and prime time for packing up and exploring North America’s favorite vacation destinations—the National Parks.

Called “the best idea we ever had”* the National parks can trace their roots to 1864 when President Abraham Lincoln deeded Yosemite Valley to the state of California. In 1872 President Ulysses S. Grant signed into law legislation that created Yellowstone Park, the first National Park. In 1906, the Antiquities Act extended protection for the country’s natural heritage to smaller features, like Devils Tower as national monuments.

The drive to preserve these areas for future generations came not just from their natural beauty but from the recognition that these areas have much to tell us about the history of the Earth.

This week: Stories from the rocks of the US National Parks and Monuments.

*By writer and historian Wallace Stegner

Darwin's pond, revisited

2010-07-09T10:50:00.002-04:00

Darwin’s “warm little pond” scenario for the origin of life on earth may not have been hot enough to do the work of chemosynthesis, combining the elements of life—CO2, methane, and water—into more complex biological compounds, and some researchers suggest that hydrothermal vents like those found today in abyssal ocean depths are a more likely candidate for the environment in which life first evolved.

Water gushing from hydrothermal events tends to be alkaline from reaction with minerals in the earth’s crust. When an alkaline hydrothermal fluid (that is, a fluid with low Hydrogen ion levels) mixes with acidic seawater (which has a higher H ion concentration), the resulting pH gradient creates potential energy that can be used to power chemical reactions by the diffusion of hydrogen ions in a process called chemiosmosis.

The oldest and simplest forms of life on Earth may have used chemiosomosis as an energy source.

Source: Nicole Branan writing in Earth, May 2010, based on research by Wm Martin and others in BioEssays

Charles Darwin & the origin of life

2010-07-08T11:23:00.002-04:00

Although best known for his ideas about the origin of species, Charles Darwin also thought about the origin of life on Earth.

In 1871 Darwin described his view of the environment in which life originated; he wrote that life may have appeared: “in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc.”.

Darwin wrote this 80 years before Stanley Miller and Harold Urey synthesized amino acids in their laboratory equivalent of Darwin’s “warm little pond”.

The Miller-Urey experiment is over 50 years old and scientists continue to revise their ideas about the conditions present in the early Earth, and the “warm little pond” scenario has been challenged by other hypotheses including one that life may have arisen under cold conditions. These scenarios will eventually sort themselves out as more research is conducted.

That’s the nature of science.

From amino acids to cells

2010-07-07T08:27:00.002-04:00

The abiotic formation of amino acids, as demonstrated by the Miller-Urey experiment, is still a long way from manufacturing a living organism, and filling in the steps between non-living and living is an area of active research involving chemists, biologists, geologists, and physicists.

The discovery of structures called protobionts provides information on how one of the next steps took place: Protobionts are aggregates of organic molecules enclosed in a membrane. These structures can form spontaneously at Earth surface conditions, for example, through alternate wetting and drying conditions that might take place naturally on a tidal flat.

Protobionts provide an analog for the step between macromolecules and cells, and the discovery of protobionts suggest that it is only a matter of time before we discover the intermediate steps between the abiotic precursors and living things.

Helpful notes on the transition from abiotic to biotic, here.

Constructing life

2010-07-06T08:11:00.002-04:00

Any recipe for life on Earth requires a source of essential elements, a source of energy to stimulate chemical reactions between these elements, and time for these reactions to take place.

In 1952 researchers at the University of Chicago took a mixture of ammonia, methane, and hydrogen to simulate the early Earth atmosphere and applied a spark to simulate a natural source of energy-lightning-and after 8 days found that amino acids—the building blocks of DNA-- had formed in this oxygen-free atmosphere.

In the half-century since this experiment scientists have modified their ideas about the composition of the early earth atmosphere, but the Miller-Urey experiment still stands as the first example of synthesizing organic compounds from inorganic precursors—a process that occurred in the Early Earth in some form, as our own existence is evidence that it happened.

For more on the Miller/Urey experiment, see this site.

What is life?

2010-07-05T06:05:00.002-04:00

The oldest fossil record of life on earth is photosynthesizing cyanobacteria found in stromatolites. However, photosynthesis is a complex process, and these cyanobacteria probably had precursors that are yet unknown. What were these first hypothetical life forms like?

To answer that question we must first decide on a definition of what constitutes a living thing. This definition is not as clear-cut as it might appear.

Living things grow and reproduce, but inorganic crystals do this, too. Viruses are not regarded as living, as they require a host in order to survive and reproduce, but the existence of viruses highlights the fuzzy line between life and non-life, and reflects the fact that life must have originated from a non-living, “prebiotic” stage.

The British biologist J.B.S. Haldane concluded that “The line between living and dead matter is …somewhere between a cell and an atom.”

Photo and information on research on artificial life here.

First continents

2010-07-02T14:31:00.002-04:00

Although we tend to think of continents as being permanent features on Earth, in fact the earliest Earth was devoid of continents.

Basaltic ocean crust formed first, as the early Earth cooled from its original molten state. Continental crust is formed through tectonic plate collisions, which involves the subduction of one plate, recycling the plate back into the Earth’s mantle, causing melting of lighter minerals and migration of this new, granitic magma upward where it solidifies, forming new continental crust.

Continental crust is less dense than ocean crust, and in a plate tectonic collision the lighter continental crust is not subducted but remains at the earth’s surface.

Continents grow by accretion of granitic crust through eons of plate collisions.

This process of continental growth and accretion continues today; much of the state of California is a mosaic of microplates that have been accreted to the west coast of North America.

Illustration from here.

Earth's first crust

2010-06-30T20:20:00.004-04:00

As Earth cooled from its molten origin, the earliest crust probably consisted of iron and magnesium-rich minerals, minerals that can crystallize at high temperatures. This assemblage of minerals forms the igneous rock basalt.

Once the Earth had cooled sufficiently for this initial crust to form, shifting plates of basaltic crust collided, one plate sinking back into the Earth’s mantle, causing the less dense minerals in the upper mantle such as quartz and feldspar, to melt, and forming a lighter, less-dense magma that erupted at the Earth’s surface in a chain of volcanoes, or island arc.

This is the same sort of tectonic activity that formed the Aleutian Islands and the islands of Japan, so we can picture the first landforms on Earth as chains of volcanic islands.

Continents would form later, as tectonic plates carrying these island arcs collided.

Illustration of a very young Earth from here.

More on early Earth from National Geographic.

Dating the Earth

2010-06-29T05:44:00.003-04:00

How did geologists determine that the Earth is 4 and a half billion years old when the oldest known rocks on Earth are only 3.8 billion years old?

Radiometric dating of meteorites--"free" samples of space rock--is one line of evidence for the age of the Earth and our solar system. Another line of evidence for the age of the Earth comes from closer to home-individual crystals of the mineral zircon found in ancient metamorphic rocks from Australia.

Zircon is a mineral that contains small amounts of radioactive uranium and thorium, so it can be radiometrically dated, and is formed by igneous processes that created the granitic crust of the continents. The Australia zircons give a radiometric date of about 4.2 billion years, indicating that the Earth’s granitic crust had developed by that time, very early in Earth's 4.6 billion-year history.

Illustration and more information about the Australian zircons available here.

Catching rays on earliest Earth

2010-06-28T20:56:00.002-04:00

The atmosphere of the early Earth was probably lacking in oxygen, as oxygen atoms were likely bonded with hydrogen in water vapor rather than what is called “free oxygen” or 02, so the first lifeforms to appear were probably anaerobes, organisms that can live in the absence of oxygen.

The absence of free oxygen in the early Earth atmosphere also meant that there was no ozone—ozone is a molecule that is formed by linking three oxygen atoms (03), and it is an effective sun block, absorbing ultraviolet radiation from the sun.

In the absence of oxygen and an ozone layer, the first lifeforms must have been extremophiles, living under conditions inhospitable to life. But the fossil record suggests that life took a foothold on Earth just as soon as conditions permitted.

(to be continued)

The illustration shows non-extremophiles protected by the ozone layer of the modern Earth. That site also explains the importance of the ozone layer.

There are many links to sites about the composition of the early Earth atmosphere. Start here.

Taking a breath on earliest Earth

2010-06-25T11:07:00.002-04:00

The Earth’s atmosphere probably had its origin in the gasses emitted by volcanoes; Earth was still very hot from its molten, impact-ridden origin, and volcanoes were abundant.

Water vapor is the most abundant component in volcanic gasses today, and this was probably the case in the early Earth as well. Ammonia, methane, and carbon dioxide are also volcanic gasses that were probably important in early Earth atmosphere.

Earth is able to retain its atmosphere because it is sufficiently large to have a gravitational force powerful enough to hang on to it, and because Earth has a magnetic field that protects it from the solar wind that would otherwise strip away the atmosphere.

The effects of not being large enough to hang onto an atmosphere can be seen on the Moon and Mercury.

For more on early Earth's atmosphere, follow this link.

Illustration is from here.

Let there be Moon

2010-06-24T10:21:00.003-04:00

Four and a half billion years ago, when the Earth was very young, it was hardly a place conducive to life. Earth was formed from the collision of planetismals, and continued to be bombarded by the debris in the early solar system for about the first billion years of its history.

Evidence of this period of intense meteorite impacts is not preserved on Earth, whose active internal tectonic engine has recycled the crust formed during this time, but is evident on our nearest celestial neighbor, the moon.

In fact, one of the impacts during this time may have formed the moon. The collision of Earth with a Mars-sized object helps to explain the similarity of moon rocks to some Earth rocks, the slightly younger age of Moon rocks, and a major impact of a large object with the Earth can account for the 23 degree tilt of the Earth on its axis.

For an overview of this and other hypotheses of lunar formation see this site.

The illustration is from here.

Let there be light

2010-06-23T08:23:00.003-04:00

About 5 billion years ago—8 billion years after the origin of the Universe--a star in one arm of the Milky Way galaxy collapsed in a supernova, forming a cloud of hot, interstellar debris.

Under the influence of gravity, this material flattened into a rotating disk, and in this rotating disk, particles collided, forming planetismals. This process can be compared to the formation of dust bunnies under the bed, although the force that attracts the dust particles is electrostatic attraction rather than gravity-driven collisions.

Planetismals collided with each other, eventually, about four and half billion years ago, forming the planets of our solar system, including Earth.

For more information on this solar nebular hypothesis of the origin of the solar system see this link or this one.

Illustration is from this site.

At the beginning

2010-06-22T08:41:00.003-04:00

To put the Earth’s history in context, our planet and our solar system formed about 4 and a half billion years ago, in a Universe that had its beginning at least 13 billion years ago.

In this beginning there was a tremendous expansion of all matter and energy in the Universe, in an event that astronomers call the Big Bang. From this event the first elementary particles such as quarks formed; after several hundred million years atoms, and elements such as hydrogen and helium formed, eventually, after a 100 million years, these elements condensed and formed the first stars.

Perhaps a billion years after the Big Bang galaxies began to form, including our own Milky Way Galaxy.

To be continued...

Links for more information on the Big Bang from the University of Michigan and NASA.

Big Bang timeline (illustration, above) from here.

Big numbers. Really. Big.

2010-06-21T10:53:00.003-04:00

This week GeoLog will begin a trip through time, exploring the physical and biological changes on Earth through the more than four-and-a-half billion years of its history, as told through the rocks and fossils that are the physical evidence of these changes. But first, a few words about our frame of reference:

Geologists tend to use numbers like 4.6 billion without a second thought. In fact, the scope of what we call geologic time is ENORMOUS and extremely hard to comprehend, especially for those of us who spend our days counting seconds, minutes and hours.

After all, our own life spans are on the order of 10s to one hundred years; known civilization goes back only thousands of years, and there were no modern humans around millions of years ago.

Our ability to comprehend the vast eras of geologic time is severely challenged by the remoteness and scope of these events.

Links for some help in visualizing these large numbers:

This site measures millions and billions in pennies, and the image of one billion pennies (above) is from here.

Teachers can find an exercise for class use on big numbers here, and the geologic time scale here and here.

T. rex: Top predator for Road Kill King?

2010-06-17T06:00:00.000-04:00

Despite its fearsome, pointed, serrated teeth and portrayal in the movies, some scientists suspect that T. rex scavenged carcasses instead of hunted down prey.

This conclusion comes from studies of modern predator/prey ecosystems, estimating the number of prey needed to support an animal of T. rex size. One group of researchers estimate that in Africa’s Serengeti grasslands, enough herbivores die daily to feed a 6,000 kg T. rex, if the dinosaur was cold-blooded, spent half a day foraging and had senses to detect carrion up to 80 meters away.

But what if T. rex were warm-blooded and had to maintain a higher metabolism? It would need more food, but it would also be able to more faster and cover more ground.

Original work: Graeme D. Ruxton and David C. Houston, 2003. could Tyrannosaurus rex have been a scavenger rather than a predator? An energetics approach. Proceedings of the Royal Society of London. B. Download their article here.

Was Sue sick?

2010-06-16T13:36:00.001-04:00

Sue, the largest, most complete Tyrannosaurus rex found to date may have been laid low by microscopic parasites.

Paleontologists have puzzled over smooth, round holes in Sue’s jaws. Originally thought to be bite marks from another T. rex, a new analysis concludes that the holes were the result of a parasitic infection that is known to affect modern avian raptors like hawks and eagles.

The infection probably caused lesions and swelling in Sue’s mouth and throat, prompting one researcher to speculate that the infection may have killed Sue as she found it increasingly hard to swallow as the infection spread, and she may have starved to death.

It is difficult to determine the cause of death for an animal that died millions of years ago, but this finding suggests that modern birds may owe their susceptibility to this parasite to their therapod ancestors.

Research from Ewan D.S. Wolff, et al., Common avian infection plagued the tyrant dinosaurs. PLoS One

Veggie rex

2010-06-14T08:00:00.000-04:00

Tyrannosaurus rex belongs to a group of dinosaurs called theropods. These dinosaurs generally have serrated, knife-like teeth that are typical of meat-eating carnivores.

The discovery of a small theropod dinosaur in China, however, shows that this group had more diversified dietary habits. This new dinosaur, named Incisivosaurus, for its large front teeth, shows wear marks on its teeth that are typical of tooth wear seen in plant-eaters.

Incisivosaurus teeth also lack the serrations typical of carnivore teeth. The discovery of a plant-eating theropod indicates that these dinosaurs were more diverse that previously thought, and occupied a variety of ecological roles in ecosystems 60 million years ago.

Source: Xu, X., Cheng, Y.-N. Wang, X.-L., and Chang, C.-H. (2002). "An unusual oviraptorosaurian dinosaur from China." Nature, 419: 291-293. For more information, click on the title of today's post.

Dino Dads

2010-06-11T08:12:00.000-04:00

Analysis of adult dinosaur bones found near nests of dinosaur eggs suggests that the male dinosaur parent was caring for the eggs.

Paleontologists from Montana State University examined the adult dinosaur bones found by these nests and discovered that they lacked a distinctive layer called medullar bone, a bone type that characterizes many species of female birds and that has been found in other dinosaurs, including Tyrannosaurus and Allosaurus.

If dino dads were in fact caring for their young, this could explain the origin of male parental care that we see in the descendents of these dinosaurs—birds. The large number of eggs found in these dinosaur nests--up to 30—also compares with the clutch size of modern birds in which the dads care for the young.

A reminder that Father's Day is coming up soon!

Summary in sciencenews.org Jan. 17, 2005 (Laura Sanders). Illustration of dino dad from here. Original research article: David J. Varricchio, et al., 2008. Avian paternal care had dinosaur origin. Science 322:1826-1828.

Birds of a feather

2010-06-10T08:30:00.003-04:00

The discovery of feathered dinosaurs led to our understanding that birds are the descendents of dinosaurs, specifically the group of dinosaurs that includes the sauropods, like Apatosaurus and the theropods like Tyrannosaurus.

However, the discovery of feather-like structures in a small dinosaur from the other major dinosaur lineage—the group that includes Triceratops and Steogsaurus—complicates things.

Tianyulong is a small herbivorous dinosaur from China with feather-like structures along its spine and tail. Paleontologists are not yet sure whether these are feathers as seen in other feathered dinosaurs, or some other sort of body covering evolutionarily unrelated to true feathers.

Scientists refer to the structures on Tianyulong as “dinofuzz”, a fitting term because this new fossil fuzzes up our picture of dinosaur-bird relationships, at least for now.

Source: Xio-ting Zheng, et al., 2009, An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures. Nature 458:333-336.

Modeling dinosaur "flight"

2010-06-09T08:34:00.004-04:00

An unusual feathered dinosaur discovered in China raises questions about the origin of flight.

Other small dinosaurs have been found with traces of feathers on the front two legs but Microraptor had feathers on the back legs, as well. Its asymmetrical feathers indicate that the animal was capable of gliding or flying, so it assumed that Microraptor made its home in trees and glided, or flew from tree to tree like modern flying squirrels.

To test these ideas, researchers at the University of Kansas constructed a model of Microraptor, using pheasant feather for its wings, and designed a slingshot to launch it. The Microraptor model glided 24 meters, or 26 yards.

Of course, a plastic model with pheasant feathers may not be an accurate model of an extinct feathered dinosaur, but it is a first step in attempting to understand how this unique animal lived.

Summarized in Earth, May, 2009, p. 13 (Emily Lant); research by David Alexander & David Burnham, University of Kansas. Click here for a video of the model's flight!

Original report on Microraptor: Xu, X., Zhou, Z., Wang, X., Kuang, X., Zhang, F. and Du, X. (2003). "Four-winged dinosaurs from China." Nature, 421(6921): 335-340, 23 Jan 2003. http://www.nature.com/nature/journal/v421/n6921/full/nature01342.html

Bulking up on veggies

2010-06-08T09:01:00.000-04:00

Sauropod dinosaurs, like Diplodocus and Brachiosaurus, hold the record for the largest land animals, weighing up to 80 tons, and stretching more than 60 meters from head to tail.

To support their size, these herbivorous dinosaurs must have spent most of their time eating and searching for food.

They had a mouthful of incisors, good for clipping off plants, but not designed for chewing. They had no molars for pulverizing their food, so they must have swallowed their food whole.

The giant bulk of these dinosaurs is more puzzling when considering their relatively tiny heads, but their small heads were supported by long necks, which may have been critical to the sauropod’s success.

Their long necks allowed these dinosaurs to stand in one place and browse vegetation from a large radius, allowing them to collect a lot of food without expending much energy.

Based on research by P. Martin Sander and Marcus Clauss, 2008. Sauropod Gigantism. Science 322: 20-201

Illustration from http://www.scorcher.ru/journal/art/art_pic/diplodocus_2.jpg

Thwarting T. rex

2010-06-07T09:01:00.000-04:00

How can an herbivore protect itself from carnivorous predators?

Strategies seen today among predators and prey of the African Serengeti apparently existed among dinosaurs in ancient ecosystems.

Paleontologists from Ohio University counted growth lines in the legbones of hadrosaurs, a group of herbivivorous duck-billed dinosaurs. By counting the number and spacing of growth rings, paleontologists can determing the animals’ age and its relative growth rate—the fast growth seen in juveniles is characterized by widely-spaced growth rings; growth slows or stops at adulthood, shown by close spacing of the growth rings.

The scientists found that hadrosaurs reached their adult size by age 13. In contrast, the carnivorous Albertosaurus reached full size at 20-30 years. Maturing quickly gave hadrosaurs an advantage over their predators, as they could produce offspring at an earlier age, and their offspring grew quickly to maturity.

Source: Drew Lee, Royal Society London B, Aug 5, 2008

Filling an empty niche

2010-06-04T08:16:00.003-04:00

Despite the occupation by reptiles of almost every ecological niche during the Mesozoic Era, there were no large planktivorous marine reptiles, the niche filled today by baleen whales.

Recent discoveries in museum drawers may hold the answer to this gap in Mesozoic reptile ecology. Fossils that had lain unstudied or incorrectly identified have been newly identified as suspension-feeding pachycormids, a group of giant bony fish.

These fish were previously thought to have been a short-lived group, limited to the Jurassic Period. Mesozoic marine reptiles may have been excluded from the large-bodied, suspension-feeding trophic niche by these supersized fish.

The pachycormids were extinct by the end of the Cretaceous Period, opening up the planktivorous niche to a new group--the whales.

Matt Friedman, et al., 100-Million-year dynasty of giant planktivorous bony fishes in the Mesozoic Seas. Science 327

A new spin on an ancient predator

2010-06-03T08:26:00.011-04:00

More than 100 years after its discovery the Middle Cambrian Burgess Shale of British Columbia Canada, continues to offer up new insight into the history of life.

One of the many enigmatic soft-bodied animals of the 500 million year old Burgess Shale of British Columbia is Nectocaris (fossil shown above) long thought to be a shrimp-like arthropod (reconstruction, above, left), but a recent study shows that the animal is most likely a cephalopod, ancestral to the group includes modern squid, octopus, and the pearly Nautilus (reconstruction above, right).

This re-classification of Nectocaris extends the geologic range of the cephalopods back 30 million years and dramatically changes hypotheses of cephalopod evolutionary history.

Nectocaris does not have an external shell, as did other ancient fossil cephalopods, and this discovery scuttles previous hypotheses that cephalopods evolved the ability to float and then swim after the evolution of their chambered shell. Nectocaris shows that cephalopods shells evolved later in cephalopod evolution, possibly in response to increased predation during the Late Cambrian.

Martin Smith and Jean-Bernard Caron, Nature 2010. Photos by the authors. Reconstructions from Discover Magazine blog

Burgess Shale redux

2010-06-02T07:54:00.004-04:00

The Middle Cambrian Burgess Shale of British Columbia, Canada, is famous for the preservation of bizarre and distinctive animal fossils, like Anomalocaris, Hallucigenia, and Marella (shown at right).

Since its discovery over 100 years ago, other Burgess Shale faunas have been found in strata of similar age around the world, but the fauna appeared to have died out by the end of the Middle Cambrian.

The recent discovery of a Burgess Shale type fauna in Morocco from rocks millions years younger than the Burgess Shale breathes life into a fauna that was thought to be long extinct--including animals like Marella, above, left.

The apparent extinction of the Burgess Shale animals was probably a result of the rarity of the exceptional circumstances required to preserve soft-bodied organisms. The discovery opens the door to finding other, younger Burgess Shale type faunas around the world.

Source and photo credit: Peter Van Roy, et al., 2010, Ordovician faunas of Burgess Shale type. Nature 465:215-218.

Happy Anniversary, GeoLog!

2010-06-01T09:57:00.005-04:00

365 days and 211 scripts ago, WPRR, public radio in Grand Rapids, Michigan, broadcast the first "GeoLog" program. GeoLog Blog reproduces the scripts along with a photo and links to the original source of the news item or other related website.

Mp3 files of GeoLog programs are now available on iTunes. Check them out at

http://www.publicrealityradio.org/programs/geolog

Tell your local radio station to pick up the program--each piece is only 1 minute long, short enough to run as a PSA (public service announcement).

Spread the word--Earth history rocks!

"Dark Earth"

2010-06-01T09:35:00.004-04:00

Astronomers estimate that the sun was up to 30% dimmer early in its history (before its internal fusion engine was up to full power), and as a consequence put out less heat. Therefore, any water on the young Earth should have been frozen.

However, rocks formed during this period of Earth history, the Archean Eon, about 3.8-2.5 billion years ago, give evidence of deposition in liquid water. This discrepancy has been called the “faint young sun paradox”.

Now there is a new explanation for a warmer-than-expected early earth: Continents were smaller and more of the surface of the Earth was covered by ocean, giving the early Earth a darker, less-reflective surface, or low albedo.

Accordingly, the Earth’s surface absorbed more of the sun’s energy than it would have with a more reflective surface, enough to keep its oceans liquid, and keeping the planet hospitable for the development of early lifeforms.

Source: Rosing, Minik T.; Bird, Dennis K.; Sleep, Norman H.; Bjerrum, Christian J., 2010, No climate paradox under the faint early Sun. Nature 464: 744–747. Also reported in Science News April 24, 2010.

Photo credit and more info on the "faint young sun paradox": http://www.astrosociety.org/pubs/mercury/35_06/paradox.html

Darwin's "Warm little pond" revisited

2010-05-31T08:57:00.004-04:00

Some researchers suggest that hydrothermal vents like those found today in abyssal ocean depths are a more likely candidate for the environment in which life first evolved.

Source: Nicole Branan writing in Earth, May 2010, based on research by Wm Martin and others in BioEssays

Photo credit: http://www.astrobio.net/exclusive/5/reflections-from-a-warm-little-pond

Footprint forensics

2010-05-13T22:49:00.003-04:00

330 million years ago, during the Carboniferous Period, a marine-dwelling arthropod hoisted itself out of the water and dragged its tail-like telson across the wet mud.

The record of this early excursion is a 6-meter-long trackway preserved in sandstone from Scotland. The trackway is attributed to a euyrpterid or “sea scorpion” whose fossil remains are known from the area.

The trackway consists of two parallel rows of footprints and a continuous groove in the middle marking the telson dragmark. The width of the trackway, indicates that the animal was 1 meter wide, and perhaps 2 meters long. The telson drag mark suggests that the animal was moving out of water, because underwater the eurypterid would not have dragged its telson.

The trackway confirms suspicions that some eurypterid could leave their aquatic habitat and venture onto land. These footprints also have the distinction of being the largest known tracks of an invertebrate.

http://news.bbc.co.uk/2/hi/uk_news/scotland/edinburgh_and_east/8632427.stm

How much wood would a woodchuck chuck...

2010-05-13T05:53:00.004-04:00

The tongue-twister about woodchucks could be asked of Castoroides ohioensis, the so-called giant beaver that inhabited North America during the last ice age, about 14,000 years ago.

The ice age animal was about twice the size of modern beavers, but, surprisingly, there is no evidence that the ice age beaver ate wood.

We are what we eat, and researchers from Michigan State University and the University of Wisconsin studied the isotopic composition of a jawbone of the ice age beaver and found that the ratio of carbon 13 to carbon 12 did not match that expected for an animal that ingested wood, but was closer to that of an animals that dined on aquatic plants.

The scientists compared the giant beaver to be, ecologically, “like little hippos.”

Source: Catherine Yansa, Geological Society of America Meeting, October 19, 2010

Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 257

Reported by Perkins, S., Science News, November 21, 2009

Illustration (inset): giant beaver compared to modern beaver. From www.nature.ca

Before "Jaws"

2010-05-12T05:54:00.003-04:00

Ichythosaurs, the dolphin-shaped, marine-dwelling reptiles of the Mesozoic Era, shared the Mesozoic seas with other reptile predators, like mosasaurs and plesiosaurs, but the discovery of a 10-meter long ichthyosaur from 240 million year old rocks in Nevada lays claim to top carnivore in Early Mesozoic marine ecosystems.

The Nevada ichythosaur has serrated teeth, previously unknown in ichythosaurs from this age. Other ichythosaurs of this time had conical teeth fit for grabbing fish and swallowing them whole, or blunt teeth suited for crushing shelly invertebrates like ammonites.

Later ichthyosaurs had serrated teeth, but did not reach the size of the Nevada specimen. This new find indicates that ichythosaurs were ecologically more diverse early in their evolutionary history than previously suspected.

Source: Nadia Frobisch, September 23, 2010, Society of Vertebrate Paleontology meeting.

Illustration from : http://www.marshalls-art.com/images/ipaleo/paleopg17/Ichthyosaurs_final.jpg

The pitter-patter of thunder lizard feet

2010-05-11T06:01:00.002-04:00

A dozen tiny, three-toed footprints were discovered in rocks about 120 million years old in coastal South Korea.

The tracks, no bigger than one and a half centimeters long, were originally made in mud, now hardened to shale, along a Jurassic riverbank. The tracks resemble those of therapod dinosaurs, the bipedal carnivores.

These tracks are not necessarily evidence of a new species of diminuative dinosaur; paleontologists previously found larger fossil footprints in the area and so these miniature tracks were probably made by a hatchling.

The size of the tracks can be used to estimate the size of the hatchling, which was probably no more than 4 centimeters at the hip. For now, these are the smallest dinosaur tracks known.

Photo credit: Kyung Soo Kim of Chinju National University of Education in Jinju, South Korea

A new fossil spider

2010-05-10T05:54:00.006-04:00

New fossil finds seem to come out of China on a weekly basis, fostered by international collaborations between Chinese and western scientists. Most famous among the Chinese discoveries are the feathered dinosaurs and rare early mammals, but there are also significant finds of humble invertebrates.

Incredibly well preserved spiders (click on the photo for an enlarged view for details) were discovered in Mongolia from rocks 120 million years old. Even though the fossil spiders are barely 5 mm long, their exceptional preservation permits paleoarachnologists to identify them as members of a modern family of spiders that previous has only been known from the USA, Mexico, Cuba, and Costa Rica.

The discovery extends the geologic range of the family 120 million years to the Middle Jurassic, and indicates that these spiders were much more widely distributed in the past.

Photo and source: Paul Selden and Diying Huang, 2010, The oldest haplogyne spider (Araneae: Plectreuridae), from the Middle Jurassic of China. Naturwissenschaften 97:

See also: Paul Selden and David Penny, 2010. Fossil Spiders. Biological Reviews 85:171-206

Going nuclear

2010-05-07T08:36:00.004-04:00

It’s clean and efficient, but reservations to using nuclear power have kept this energy alternative from growing.

Nuclear plant accidents, the accidental release of radiation into the environment, although rare, make headline news, as in the 1979 accident at Pennsylvanian's Three-Mile Island reactor and the 1986 accident at the Chernobyl reactor in the former Soviet Union.

A larger concern is how to dispose of the radioactive waste produced by nuclear power plants. This waste will remain radioactive for hundreds or thousands of years. Improved technologies and new materials can help to minimize these concerns, still, our generation faces the considerable challenge of designing a radioactive waste disposal plan that will endure for many generations to come.

Illustration: schematic diagram of a nuclear power plant. From http://www.hk-phy.org/energy/power/print/nuclear_phy_print_e.html

Blowin' in the wind

2010-05-06T08:34:00.002-04:00

Energy from the sun can be harnessed directly, by solar panels, but the sun is also the source for another form of energy.

Heat from the sun sets wind into motion. Wind energy has been harnessed for hundreds of years to power sailing ships and windmills. Sleek, modern wind turbines convert wind energy to electricity, and “wind farms” are cropping up atop ridges and wherever there is a strong, steady wind.

Large-scale production of wind energy requires a lot of wind turbines and therefore a lot of land and some people find the large wind generators noisy or unsightly. We cannot fill our gas tanks directly with wind or sunshine, but these alternative energy sources hold promise for future development.

Photo: a wind turbine from http://www-personal.umich.edu/~dopila/files/wind-turbine.jpg

Let the sunshine in

2010-05-05T08:01:00.003-04:00

Why use fossil fuels when you can tap the sun’s energy directly?

Photovoltaic cells convert sunlight into electricity, and are already widely used to power small electronic devices, like calculators. Solar panels are added to roofs in certain parts of the country, for heating homes or providing hot water.

Solar energy is relatively cheap and clean, and it’s renewable as long as the sun shines, which should be for billions of years to come.

The downside to solar energy is that it is most effectively used in sunny areas, and large-scale use of solar power requires many acres of land for the solar collectors. Still, advances in solar cell research and technology forecast a (ahem) bright future for solar power.

Photo: array of solar panels, from http://is.njit.edu/competition/2009/Cat2_2_Winner_Group142/

Dam it

2010-05-04T07:53:00.002-04:00

We’ve come a long way from the first water-powered mills that were located along rushing streams; today’s hydroelectric plants have been carved out of landscapes that are dramatically changed as a result.

Damming a river and creating a reservoir results in the loss of land and habitats upstream of the dam, and changes the dynamics of the entire river system. Dams and reservoirs have a finite lifespan, on the order of 20 -200 years, and maintaining them can be costly.

But dams bring life to the desert and reservoirs provide recreational opportunities not otherwise possible in arid regions. As with all decisions regarding potential energy sources, there are trade-offs and consequences.

Photo credit: View of Hoover Dam, http://geochange.er.usgs.gov/sw/changes/natural/codrought/

Alternative Energy: Water

2010-05-03T08:56:00.003-04:00

This week: Alternative energy

Fossil fuels are relative newcomers as energy sources. For as long as water has been running downhill, there has been a cheap, renewable, readily available energy source.

The energy created by water flowing downhill under the influence of gravity has been harnessed for hundreds of years. Factories in the 19th century were built at waterfalls or along rivers where the energy of flowing water could directly turn the waterwheel that drove their machinery.

In modern times, this energy is used to turn turbines that create electricity for distribution over power lines to large areas. Hydroelectric power is relatively inexpensive, clean, it produces no greenhouse gasses or smog, and it is renewable for as long as water can be made to run downhill.

Tomorrow: is there a downside to hydroelectric power?

Photo credit: http://www.top-alternative-energy-sources.com/images/water-wheel.jpg

Flood prevention

2010-04-30T08:07:00.004-04:00

Flooding is a natural process, an annually recurring player in the shaping and re-shaping of Earth’s surface.

Floods are really only a problem when they intersect human activity, so the most effective flood prevention program is one that removes humans from the path of potential floods and bans activities that exacerbate flooding.

It would seem obvious that no one should live in the path of potential flooding, on a river flood plain or a coast vulnerable to storm surge, but flood plains and coastal beaches are desirable real estate.

Engineering solutions like dikes and levees may help stem flooding in the short term, but geologists view coasts and rivers as parts of dynamic systems, and time has shown that alterations to one part of the system will cause a response in another part of the system, often unanticipated and unintended.

The Watershed protection and flood prevention Act, originally enacted in 1954 was designed to address these issues: http://www.nrcs.usda.gov/Programs/watershed/pl56631705.pdf

Predicting flood paths

2010-04-29T07:55:00.003-04:00

A team of geologists and physicists are modeling flooding in the laboratory to help predict the size and the route of floods from overflowing rivers.

The team was prompted to study the problem in the aftermath of the August 18, 2008 flood of the Kosi River in northern India. This flood displaced more than a million people. The scientists noticed that after overflowing its banks, the flood waters followed older, abandoned channels.

By constructing a scale model of a river-delta system in the lab, the researchers were able to determine that the initial formation of a river channel is random, but once channels formed, flooding was restricted to the previously formed channels rather than cutting new ones.

The scientists compared river flooding to earthquakes: just as earthquakes occur along pre-existing faults, flooding occurs along pre-established channels.

From March 19, 2010 post at http://www.terradaily.com/reports/Catastrophic_Flooding_May_Be_More_Predictable_999.html

Based on current issue of Geophysical Research Letters, Reitz, Meredith, et al.

Photo credit: http://www.geo.uu.nl/fg/palaeogeography/researchprogram

Transgressions of a different sort

2010-04-28T08:13:00.003-04:00

Before fossils were understood to be the actual remains of once-living plants and animals, they were regarded in some quarters as tricks of the devil, planted by the fallen one to test the fidelity of the faithful.

After all, fossils of animals that clearly lived in the ocean were found far from any modern ocean (like those fossil clams in Nebraska mentioned in an earlier post) and even on the tops of mountains.

At a time when the Earth and everything in it was understood to be unchanged from its original creation, fossils of marine invertebrates on mountain tops were problematic, and a divinely sent global flood was an explanation that conformed both to the observations and to the philosophical framework of the time.

We now understand the dynamic nature of the Earth and can explain these observations in terms of mechanisms like plate tectonics and glaciation.

Illustration: The last major transgression of the sea over North America formed a seaway that reached from the Gulf of Mexico to the Arctic during the Cretaceous Period (144-65 million years ago). From http://www.emporia.edu/earthsci/student/mcgee2/hipln005.jpg

What about Noah?

2010-04-27T10:02:00.003-04:00

The greatest flood story ever told is recorded in religious texts, a story of world-wide inundation precipitated, if you will, by a God angry at his faithless people.

The purpose of the story is to teach a moral lesson, not a meteorological one, but many such stories are rooted in experience. The half-meter rise in sea-level that resulted from the discharge of water from Glacial Lake Agassiz doesn’t sound like much, but in low-lying coastal areas the effect could have moved shorelines inland up to 10 kilometers.

The resulting flood would have forced ancient peoples to flee their coastal settlements, and lacking any knowledge of the glacial lake responsible for the floodwaters, the people created a story that helped explain both how and why the flood occurred.

Source: Teller, J.T., and Leverington, D.W., Outbursts from Lake Agassiz and their possible impact on coastal environments. Environmental Catastrophes and recoveries in the Holocene, August 29-Sept. 2, 2002, Brunel University, Uxbridge, UK. Also mentioned in a 2002 piece in Science News by Sid Perkins.

Photo credit: http://www.maritimequest.com/misc_ships/noahs_ark_3000bc/noahs_ark_4.jpg

Flooding on a continental scale

2010-04-26T09:12:00.004-04:00

Why are there fossils of marine animals found in the sedimentary rocks of Nebraska, (or any other place far from today’s oceans where marine fossils are found)?

These fossils are evidence that ancient seas once covered the continents, leaving in their wake, the sediments and fossils deposited in the sea. Throughout Earth’s history, sea-level has risen and fallen, in response to glacial periods and changes in the rate of plate tectonic movement.

During glacial periods, water evaporated from the oceans falls as snow and is tied up in ice sheets on land, causing sea-level to fall—a regression in geologic terms. Melting ice returns water to the oceans, causing sea-level rise, and water from the deep ocean basins surrounding the continents laps up over the continents in what geologists term a transgression.

Illustration: North America during the Ordovician Period (about 440 million years ago). State boundaries are lightly dotted in; the light blue represents sea water overlapping--transgressing--the continent from the deep ocean basin (dark blue) From http://jan.ucc.nau.edu/~rcb7/namO450.jpg

Future floods?

2010-04-23T10:06:00.003-04:00

The Earth is much more heavily populated today than it was when the great Ice Age floods occurred. If floods of the magnitude that resulted from the draining of Lake Agassiz or carving the Scablands were to happen today, the impact on humanity would be catastrophic.

Fortunately, the risk of huge, glacially induced floods like those of the Pleistocene is negligible. The mega floods of the Pleistocene were associated with continental ice sheets. Today, the only remaining continental ice sheets are in Greenland and Antarctica, and neither land mass contains large ice-dammed lakes.

Iceland’s volcanism can produce sub-glacial lakes that could cause flooding there, but not on the scale of the megafloods of the Pleistocene.

That isn’t to say that Earth is free of flood hazards; if global warming were to melt the continental ice sheets sea-level would rise 215 feet or 65 meters* but that’s another story.

* http://www.usatoday.com/weather/resources/askjack/2004-11-21-melting-polar-ice_x.htm

Image: World map showing sea level if all current ice were to melt http://www.johnstonsarchive.net/spaceart/earthicefree.jpg

Lake Agassiz

2010-04-22T05:56:00.003-04:00

During the last ice age, a 700-mile long by 200-mile wide lake centered on the province of Manitoba covered central Canada, dammed by glacial ice.

Named Glacial Lake Agassiz, for the famous Swiss scientist and later Harvard professor Louis Agassiz, who was among the first to recognize landforms that indicated that vast continental ice sheets once covered the continents, the lake drained catastrophically when the ice dam collapsed.

Water tied up in glaciers and in glacial lakes during the last ice age caused sea-level to drop more than 100 meters. At its maximum extent, Glacial Lake Agassiz was the largest body of fresh water on the planet, and held more water than all the worlds lakes today. When the climate warmed and the ice dam was breeched, the resulting flood raised global sea levels by half a meter.

More info: http://www.cloudnet.com/~edrbsass/agassiz.htm

Source: Perkins, Sid, Once Upon a Lake, Science News November 2, 2002 v. 162:p. 283

Illustration credit: Maximum extent of Glacial Lake Agassiz,

http://mrbdc.mnsu.edu/mnbasin/fact_sheets/valley_formation.html

Channeled Scablands

2010-04-21T06:03:00.002-04:00

Geologists long recognized that something was odd about the landscape of eastern Washington state. The landscape is marked by dry canyons and deeply eroded basalt flows—the channeled scablands. In other areas, parallel ridges of undulating low hills cover the bedrock.

In the 1920s geologist J Harlen Bretz interpreted these features as the result of erosion and deposition from floods originating with the breach of glacially dammed lakes—the ripple-shaped hills (shown in the aerial view photo) were exactly that—giant ripples deposited by enormous outpouring of water from Glacial Lake Missoula.

The channeled scablands formed around 15,000 years ago after an ice dam holding back the waters of glacial Lake Missoula failed, sending 2,000 cubic kilometers of water rushing through the breach and reshaping the landscape in a matter of days.

Further info: http://www.nps.gov/history/history/online_books/geology/publications/inf/72-2/intro.htm

Photo credit: http://hypography.com/forums/earth-science/12606-missoula-floods-channeled-scablands-drumheller-channels.html

Before the Chunnel

2010-04-20T05:35:00.004-04:00

Half a million years ago England and France shared a land connection that also formed the dam for a glacial lake that covered much of northern Europe.

The soft chalk bedrock dam was breached by the waters of the glacial lake between 450 and 180 thousand years ago, forming the Strait of Dover. As with the torrent that breached the Straits of Gibraltar and filled the Mediterranean, modeling indicates that waters rushed through the Dover Strait at rates up to 1 million cubic meters per second.

The evidence for this rush of water comes from sonar imaging of the submerged valley carved by the flood waters. Broad grooves up to 100 meters wide and 15 km long were carved into the valley floor. These features indicate high flow rates, and are associated with other mega floods.

Source: Birth of an Island: Megaflood severed Europe from Britain. SN July 21, 2007, v. 172, p. 35; based on Gupta, S., et al., 2007. Nature July 19

Illustration credit: http://islesproject.com/2009/01/12/450000bce-200000bce-the-origins-of-island-consciousness-the-torrent-that-created-the-english-channel/

Real flood geology

2010-04-19T10:02:00.003-04:00

Imagine a dry basin where the Mediterranean now sits. 5.6 million years ago the Mediterranean was closed off from the Atlantic Ocean by tectonic uplift, and its waters gradually evaporated, leaving behind tell-tale deposits of evaporate minerals and creating what geologists call the Messinian salinity crisis.

About 5 million years ago Atlantic waters breached the barrier at the Strait of Gibraltar creating an enormous flood. Recent modeling indicated that water may have poured into the Mediterranean basin at a rate 1,000 times the flow of today’s Amazon River, filling the basin in less than two years—a geological blink of an eye.

Source: Daniel Garcia-CAstellanos, et al, December 10, 2009 Nature.

Illustration credit: http://records.viu.ca/~earles/messinian-crisis-apr03.htm

Shields up, Scotty

2010-04-16T06:00:00.004-04:00

Early Earth was a rough place for life to gain a foothold.

One of the questions facing scientists is just when the earth’s protective magnetic field was strong enough to shield its inhabitants from harmful cosmic radiation.

Ancient rocks from South Africa indicate that a magnetic field 50-70 percent the strength of today’s magnetic field was in place by 3.4 billion years ago.

The evidence comes from nanometer-sized crystals of the mineral magnetite embedded in millimeter-sized quartz crystals. Quartz is the most stable mineral in the Earth’s crust and a good time capsule for the included magnetite. A magnetometer is used to detect the magnetic signal preserved in the iron atoms in the magnetite and to measure the strength and orientation of the ancient magnetic field.

[Note: Not just any rocks can be used in analyses in dating ancient geological events, because millennia of deformation and reworking of the Earth’s crust could re-set geological timepieces, so great care is taken in selecting the best candidates for dating.]

Source: Tarduno, John, et al., March 5, 2010 Science.

Grossman, Lisa, Shields were up on early Earth. Science News March 27, 2010, p. 12.

Bridging the gap

2010-04-15T06:01:00.002-04:00

The island of Madagascar is separated from Africa by the Mozambique Channel, 460 km across at its narrowest point and up to 3,000 meters deep. Scientists have long debated how the four-legged inhabitants of Madagascar got there, especially the non-aquatic ones.

Seventy years ago paleontologist George Gaylord Simpson proposed a “sweepstakes” model in which small vertebrates could have been transported from the African mainland to Madagascar on natural rafts of floating vegetation.

The problem with Simpson’s idea was that today’s currents flow westward from Madagascar towards Africa. But 60 million years ago continents lay in different positions, and new paleo-oceanographic modeling shows that there was a strong current from Africa to Madagascar, which would have provided the route for the sweepstakes rafts with their accidental migrants onboard.

It took a while, but Simpson's 20th century hypothesis was verified with the help of 21st century technology.

References: http://www.oceandots.com/indian/mozambique-channel/

Ali, Jason R., and Huber, Matthew, 2010. Mammalian biodiversity on Madagascar contolled by ocean currents. Nature 463: February 4

Map is from http://www.embassy.org/madagascar/madagasc.jpg

First footprints, revisited

2010-04-14T08:10:00.004-04:00

GeoLog has previously reported on the first footprints made on land, tracks in 530-million year old sandstone made by some sort of invertebrate animal, probably an arthropod—a millipede, perhaps. Now comes word of the oldest known footprints of a four-legged vertebrate, or tetrapod, in rocks 395 million years old.

This find is significant because the tracks predate the oldest known tetrapod body fossils by 18 million years, and if these tracks are indeed made by tetrapods, the find would push back the timing of the vertebrate transition from water to land.

In the absence of accompanying body fossils, it is difficult to definitively match trackways with track-makers, and one alternative explanation is that these trackways could have been made by lobe-finned fishes, precursors to the tetrapods.

[One more note: The trackways represent several different animals ranging from an estimated 50 centimeters long to 2 and a half meters long—quite a large animal for so early in tetrapod evolution.]

Sources: Grzegorz Niedźwiedzki, Piotr Szrek, Katarzyna Narkiewicz, Marek Narkiewicz & Per E. Ahlberg ^{Nature 463, 43-48 (7 January 2010) Tetrapod trackways from the early Middle Devonian period of Poland}

Perkins, S., 2010, Fossil footprints could push back origin of first four-limbed animals. Science News January 30, 2010.

Battling Beetles

2010-04-12T09:13:00.003-04:00

Antlers and horns are usually associated with the male of the species, but sometimes the females bear battle armor.

Female dung beetles have horns that are used in challenging other female dung beetles for dung. Dung beetles lay their eggs in dung, and researchers have found that females with more robust horns produced more offspring than females of similar size but with smaller horns.

Experiments also showed that, unlike males, who may sport extravagant ornament to advertise their superior genetic makeup and suitability as a mate, female ornament does not play a role in sexual selection, at least among dung beetles. So it appears that development of showy weaponry in female dung beetles is related to survival in procuring resources, while in males it functions for survival of a different sort.

Sources: Millus, S., Female beetles ready for dung wars. Science News March 27, 2010

Watson, Nicola and Simmons, Leigh, Proceedings of the royal Society B, March 3, 2010

Watson and Simmons, Behavioral Ecology, March-April, 2010

Photo credit: Sean Stankowski

"Just a theory"

2010-04-09T07:55:00.002-04:00

If you want to rile up a scientist, tell them that their understanding of how the world works is “just a theory.”

Remember, in scientific usage a theory is the strongest statement of confidence in explaining the natural world. The most powerful theories tie together apparently unrelated observations.

Evolutionary theory, including the hypothesis of common descent of all living things, is supported by observations as different as paleontological data—the sequence of fossils preserved in the sedimentary rock record; data from biogeography—the modern and fossil distribution of organisms world-wide; data from molecular biology--the close match between human and other primate DNA, data from comparative anatomy—the structural similarities between the skeletal systems of vertebrates from fish to mammals, data from developmental embryology—the discovery of genes common to all vertebrate groups and the role they play in development; among others.

In the sense of having broad support across many different scientific disciplines, evolutionary theory is much more strongly supported than gravitational theory.

Cartoon credit: http://wever.wordpress.com/2008/05/21/

Science & "not-science": telling the difference

2010-04-08T08:57:00.003-04:00

The test of whether a proposed explanation is scientific or not is….a test. In the jargon of the scientific method, a proposed explanation must be falsifiable, that is, amenable to being supported or rejected through repeated experiments and retain its explanatory power in the face of new observations or interpretations.

Falsifiability is another way of asking whether an explanation is subject to change. Has the explanation changed with advances in understanding? Science is self-correcting through ongoing testing and re-evaluation.

Secondly, consider the source. Is the explanation from a reliable source? Science is what reputable scientists do. Just as we would not consult an electrician for a toothache, we would not consult religious texts for scientific explanations.

And third, consider, Does the explanation tie together previously seemingly unrelated observations? The best theories do this--Big Bang theory in astronomy, Plate tectonic theory in geology, and Evolutionary theory in biology.

Cartoon is from http://stepsandleaps.files.wordpress.com/2009/08/the-scientific-method.jpg

Science & Religion: Viva la difference!

2010-04-07T09:13:00.003-04:00

Religious belief or faith is an example of a non-scientific way of understanding the universe.

The Apostle Paul defined faith as “being sure of what we hope for and certain of what we do not see” (Hebrews 11:1, New International Version). Faith and religious belief, while essential elements of what makes us human, describe an area outside of scientific inquiry.

The faithful are exhorted to having faith like a rock, unmoving, unchanging, solid; all important qualities in a belief system, but qualities that are counterproductive to scientific inquiry.

Our scientific understanding of the universe—where it came from, how it evolves—continues to change with new observations, new data. Our philosophical understanding of our place in the universe, why we are here, what our purpose is, is the purview of philosophy and religion.

Science and religion are different ways of understanding the universe, both important but occupying separate realms.

Photo credit: http://www.cuttingedge.org/NEWS/earth7.jpg