Geology of Vacation Destinations

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

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The pitter-patter of thunder lizard feet

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The tracks, no bigger than one and a half centimeters long, were originally made in mud, now hardened to shale, along a Jurassic riverbank.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

Going nuclear

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

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

Dam it

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

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

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

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

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?

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

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?

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

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

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

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/

Charles Darwin, Geologist

Although more widely remembered for his contributions to the biological sciences, Charles Darwin first made his scientific reputation as a geologist.

His formal geological training was limited, but intense; he accompanied the eminent geologist Adam Sedgwick "geologising", that is,describing and mapping the rocks of Wales and learning the ways of the field geologist.

A few months later Darwin was on board the Beagle, with a volume of Charles Lyell’s new book, Principles of Geology. Lyell was the foremost geologist of the day. With this as his guide, Darwin made observations during the voyage that led to publications on the formation of coral reefs and volcanic islands and the geology of South America, contributions that still stand, today.

Photo: Rocks collected by Charles Darwin during his voyage on the Beagle. credit: http://www.flickr.com/photos/gruts/3802735409/

Darwin & the Beagle

The seminal event in Charles Darwin’s life was his 5-year voyage around the world on the HMS Beagle.

Darwin kept extensive notebooks of his observations on the plants, animals, fossils, and rocks of the areas he visited.. Darwin’s voyage is most widely remembered for the visit to the Galapagos Islands off the coast of Ecuador, and for the unique animals that inhabited each island, like the marine iguanas, huge tortoises, and birds, but during the voyage Darwin also made the first geological maps of parts of South America, discovered fossils of previously unknown species of extinct South American mammals, and figured out how coral atolls formed.

Darwin returned to England with observations enough to occupy his thoughts for the rest of his long life.

Photo credit: http://theora.com/images/HMS%20Beagle.jpg