August 17th, 2006 11:49 EST
U.S., European Researchers Explore Geologic History of Alps
Washington – Periods of dramatic climate change millions of years ago shaped the Alps as they stand today, according to collaborative findings from an Italian, Swiss and U.S. research team.
The mountain chain once extended 48-80 kilometers farther south into northern Italy than it does today, according to a paper published in the August edition of the journal Geology. The U.S. National Science Foundation funded the work.
The Alps were likely 100-200 kilometers wider and 300-1520 meters higher than they are today, before they were diminished by a massive erosion event 3 million years ago.
“At one time, what is now Milan [Italy] would have been in the foothills of the Alps,” said Sean Willett, a University of Washington geologist. “But the Alps never regained the size they had at the end of the Miocene,” a geologic era that extends roughly from 23 million to 5 million years before the present.
Willett is the lead author of the Geology paper, along with co-authors Fritz Schlunegger of the University of Bern in Switzerland and Vincenzo Picotti of the University of Bologna in Italy.
The planet was relatively warm and wet during the period under study. The Miocene also was marked by an event geologists call the Missinian salinity crisis, which occurred when the Mediterranean Sea had no outlet to the rest of the world’s oceans.
Evaporation greatly reduced the level of the sea, and the beds of rivers flowing from the Alps dropped along with the rest of the Mediterranean basin.
Falling land levels caused serious erosion, the scientific team found, creating many of the distinctive deep valleys for which the Alps are known. The erosion also created a dozen major lakes that are distinctive features of the Alps today.
The research concludes that the Mediterranean substantially refilled with fresh water, probably with heavy rainfall, an indicator of climate change.
About 200,000 years later, the Atlantic Ocean finally breached Gibraltar and seawater poured back into the basin between what we now know as Southern Europe and Northern Africa.
After 3 million years of warm and wet conditions, the climate cooled again and glaciers formed in the Alps.
A press release on the study is available on the University of Washington Web site.
(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)