Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The First True View of Global Erosion

28.07.2011
Every mountain and hill shall be made low, declared the ancient prophet Isaiah. In other words: erosion happens. But for the modern geologist a vexing question remains: how fast does this erosion happen?

For more than a century, scientists have looked for ways to measure and compare erosion rates across differing landscapes around the globe—but with limited success.

“Knowing the background rate of erosion for a place is extremely important,” says University of Vermont geologist Paul Bierman, “if you want to compare it to what’s coming off the landscape today because of human impacts like agriculture, development, and forestry.”

Since the mid-1980’s, measurements of a rare radioactive element—beryllium-10 that appears in quartz bombarded by cosmic rays in the top few feet of Earth’s surface—have greatly improved geologists’ ability to estimate erosion rates. But these experiments have been done on a local or regional scale, using a variety of methods, calculation constants, and corrections. Comparisons between climate zones and differing rock types have been difficult—cutting off a global perspective.

Now Bierman and his graduate student, Eric Portenga, have taken twenty years worth of this disparate data, compiled 1599 measurements from eighty-seven sites around the world, and recalculated it with a single, up-to-date method.

Their work, “provides the first broad, standardized view of pre-human, geologic erosion rates,” they write in “Understanding Earth’s eroding surface with 10Be,” published in the August edition of GSA Today, an open-access journal, available online July 26, 2011.

Sustainable Soil

“Nobody has stepped back far enough to look at this big picture,” says Bierman, “we all work on our little postage stamps of the world—Africa, South America, the western US.” But many of the pressing questions about erosion are global in scale.

Most urgent, the ability to support the nine billion people forecast to be living on Earth by mid-century rests directly on the resiliency of soil systems and the health of water supplies. And these two pillars of sustainability are directly and deeply affected by erosion.

The method used in this new study can provide a good tool for measuring the sustainability of modern agricultural practices, Bierman notes, since the beryllium-10 data shows the rate at which landscapes have been changing in the recent geologic past: the last thousand to several-hundred-thousand years. “If human impacts result in rates faster than we measure, it’s non-sustainable,” he says.

Portenga sees how this study can help managers in contested landscapes like the Chesapeake Bay. “Regulators may want to stipulate an ideal amount of sediment coming out of a river system and they may say that they want to get this back to ‘normal’ standards or ‘normal rate.’ But what is that rate? What was the erosion like before people started interacting with the landscape?” he says.

Not being able to answer that question well has contributed to many regulatory conflicts. “This work can help give a better idea of what is normal,” says Portenga, who was the lead author on the study.

No Smoking Gun

This new study also goes fairly far in identifying the environmental factors—including latitude, annual precipitation, and, especially, slope—that drive erosion rates in drainage basins. The mechanisms controlling erosion on outcrops of bedrock are less clear.

Using several statistical tests, Portenga and Bierman were able to explain about sixty percent of what controls differing erosion rates in drainage basins around the world. But their study only explains about thirty percent of the variability between outcrops of bedrock. “This means geologists are missing a lot of the crucial information about what is controlling bedrock erosion,” Portenga says.

Little-studied variables—like the density of fractures in bedrock, the strength of rocks, and their chemistry—may be controlling erosion rates, the study suggests.

“I don’t think we’ll ever find the single smoking gun of erosion,” says Portenga, “the natural world is so complex and there are so many factors that contribute to how landscapes change over time. But as this method develops, we will have a better sense of what variables are important—and which are not—in this erosion story.”

For example, it has been a truism of geology for decades that rainfall is the biggest driver of erosion. Semi-arid landscapes with little vegetation and occasional major storms were understood to have the greatest rates of erosion. But this study challenges that idea. “It turns out that the greatest control on erosion is not mean annual precipitation,” says Bierman. Instead, look at slope.

“People had always thought slope was important,” Beirman says, “but these data show that slope is really important.”

Modeling the Future

Their new study, supported by the National Science Foundation, is part of a larger long-term goal of creating a global model that can predict the background rate and patterns of erosion across the whole planet—and how these erosion rates will respond to changes like human-induced climate change.

“Following this study, we can start to answer big questions like, ‘how does climate drive erosion?’” says Bierman. In other words, a clearer picture of what global erosion has looked like in the recent past will start to illuminate what is likely to happen in the future as human impacts and land-use decisions play out.

“We want a predictive model,” says Bierman, “we want to be able to have somebody say, ‘here’s my drainage basin, here’s the climate, here’s the rock type, here’s the slope, here’s the mean annual precipitation: how quickly is this eroding?’ That’s what you need for land management.”

Joshua Brown | EurekAlert!
Further information:
http://www.uvm.edu

More articles from Earth Sciences:

nachricht Water cooling for the Earth's crust
22.11.2017 | Helmholtz Centre for Ocean Research Kiel (GEOMAR)

nachricht Retreating permafrost coasts threaten the fragile Arctic environment
22.11.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Corporate coworking as a driver of innovation

22.11.2017 | Business and Finance

PPPL scientists deliver new high-resolution diagnostic to national laser facility

22.11.2017 | Physics and Astronomy

Quantum optics allows us to abandon expensive lasers in spectroscopy

22.11.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>