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The Watershed protection and flood prevention Act, originally enacted in 1954 was designed to address these issues: http://www.nrcs.usda.gov/Programs/watershed/pl56631705.pdf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

Real flood geology

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

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

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

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

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"

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

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!

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

When a "theory" isn't a theory

Many non-scientists use the words“hypothesis” and “theory” interchangeably (if they use ‘hypothesis” at all) and as synonyms for “idea.”

To a scientist, hypotheses are much more than an idea, much more than an “educated guess”; they are possible explanations based on numerous and repeatable observations (data). In the hierarchy of the scientific method, a theory is an even stronger statement than hypothesis.

The American Association for the Advancement of Science (AAAS), the top scientific society in the United States, defines “theory” as “a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Hypotheses and theories may begin as a bright idea, but they are so much more.

*(http://www.aaas.org/news/press_room/evolution/qanda.shtml accessed 3-25-10)

photo credit: http://www.dreamstime.com/stock-images-dreamstime-download-free-stock-images-and-photos-image1940874

The fact about facts

Scientists do not often speak in terms of “facts” because they live the adage, “the more you know, the more you know you don’t know.” Instead of speaking in simple, declarative sentences scientists are more likely to tag caveats onto their statements along the lines of, “this is the best explanation we have with the data available to us at this time”; a style of communication that both the layperson and the news reporter find highly unsatisfying.

Caveats appended to scientific research tend to get dropped in the translation into seconds-long sound bytes and the popular print and digital media. Even textbooks sacrifice technical detail for grade-level-appropriate content and breadth of coverage.

Compounding the confusion between “facts” and “non-facts” is the discrepancy between the scientists’ use of the words “hypothesis” and “theory”— More next time.

Cartoon credit: thadguy.com

Science & Change

In its day, the pre-Copernican interpretation that the sun and other planets revolved around the Earth was the prevailing theory of planetary motion. The fact that the pre-Copernican explanation is not accepted today points to another fundamental characteristic of scientific theories—they are subject to change. We now know that the Sun, not the Earth, is the center of our solar system, and our modern theories of planetary motion reflect this newer understanding.


The fact that theories change as the result of new information coming to light is evidence of the scientific nature of these earlier explanations. So-called “theories” that do not change in light of new data or understanding are not scientific, are not part of a scientific way of understanding the universe, and are not a part of scientific inquiry.

Photo credit: http://helensguidetothegalaxy.files.wordpress.com/2009/04/001-solar_system-my-fantasy.jpg

World turned upside-down

Workers with the Paleo Division of New Mexico State Resources recently uncovered a fossil that sent shock waves through the scientific community and that will require the re-writing of textbooks on paleontology, evolution, and the history of life.

Working in the 140 million-year-old Morrison Formation the team discovered a skull and partial skeleton of the dinosaur Allosaurus with a fossil hominid trapped between its gaping jaws.

Of course, this find is evidence that humans and dinosaurs did in fact live at the same time, and it casts doubt on many other aspects of evolution, which of course, is only a theory, anyway. The discovery was announced by Lirpa Loof, which should explain any remaining confusion on the significance of the event.

The full story is at http://www.nmsr.org/Archive.html

Explanation at http://www.nmsr.org/april_fool.html

New Mexicans for Science and Reason http://www.nmsr.org/