Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Climate change was major factor in erosion of Alps 6 million years ago

17.08.2006
The Alps, the iconic rugged mountains that cover parts of seven European nations, might have reached their zenith millions of years ago, some scientists believe, and now are a mere shadow of their former selves. New research offers an explanation.

A team led by Sean Willett, a University of Washington geologist, has found that the culprit is likely massive erosion, triggered by a sudden drop in the level of the Mediterranean Sea 6 million years ago and then prolonged by a warmer, wetter climate.

Typically mountain ranges reach a sort of equilibrium, with erosion more or less keeping pace with the tectonic forces that enlarge the mountains. But an event called the Messinian salinity crisis, precipitated by blockage of the forerunner of the Strait of Gibraltar, cut the Mediterranean off from the rest of the world's oceans. Evaporation greatly reduced the water level, dropping it as much as two or three miles below the rest of the world's ocean surfaces.

The beds of rivers flowing from the Alps dropped sharply as the level of the Mediterranean basin fell, and their force carried away huge amounts of sediment. The forces carved many of the distinctive deep valleys for which the Alps are known and left behind nearly a dozen major alpine lakes in the southern Alps.

"The erosion rates were 10 times normal in the salinity crisis, and that correlates to the fall of the base level of the rivers," said Willett, a UW associate professor of Earth and space sciences. "We think that jump-started the erosion, but it doesn't explain why the erosion stayed so high for 3 million years. The Mediterranean was low only for 20,000 to 80,000 years before it refilled."

The Mediterranean substantially refilled with fresh water, likely from heavy rainfall, indicating major climate change. The result was a brackish water mixture that probably continued to evaporate at high levels, Willett said. About 200,000 years later, the Atlantic Ocean finally breached Gibraltar and seawater poured in, apparently refilling the Mediterranean completely within a few years.

"Probably the biggest erosion came when there was both the heavy rainfall and the low base level of the rivers," he said.

Willett is the lead author of a paper describing the findings, published in the August edition of the journal Geology. Co-authors are Fritz Schlunegger of the University of Bern in Switzerland and Vincenzo Picotti of the University of Bologna in Italy. The work was funded by the National Science Foundation.

The scientists studied geological structures associated with the Alps, particularly faults at the southernmost edge of the mountain range, in northern Italy. They found numerous faults buried beneath the surface of the plain adjacent to the Po River, which flows through Italy's largest industrial region and is the nation's longest river.

The fault that lies farthest south, now inactive, is beneath the city of Milan, evidence that the Alps used to extend that far south, Willett said. Now the mountains are 30 to 50 miles away.

"At one time what is now Milan would have been in the foothills of the Alps," he said. "But the Alps never regained the size they had at the end of the Miocene."

The researchers found that the greatly increased erosion came at the same time that the faults associated with the Alps stopped moving. Less erosion would be expected as tectonic forces decline, Willett said, but instead there was vastly more sediment removed from the mountains at the time the fault motion stopped.

Before the massive erosion, he said, the Alps likely were 60 to 120 miles wider than they are today, and 1,000 to 5,000 feet higher. The highest point today is Mount Blanc on the border of France and Italy, at about 15,700 feet. It is likely that erosion took a toll on the northern edges of the Alps as well, Willett said.

After 3 million years of warm and wet conditions, the climate cooled again and glaciers formed in the Alps, though they are again in decline now because of climate warming. Willett noted that European precipitation is strongly linked to changes in the global mean temperature, which scientists can track over time through ice records.

"What is fascinating to me is that we show how complicated and coupled the Earth system is," he said. "You have to understand one part of the system to understand how other parts of it work together."

Vince Stricherz | EurekAlert!
Further information:
http://www.washington.edu

More articles from Earth Sciences:

nachricht Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>