Climate may be responsible for up to half of the height of the Transantarctic Mountain range in East Antarctica, according to new research. Cold weather during the Ice Ages also appears to have been a key player in shaping the mountains of North America and Europe.
In very cold climates, glaciers slide through the terrain, cutting deeper into valleys and gouging new ones. The glaciers carry rocky debris away as they travel, which lightens the load on the crust below. Because Earth tends to keep a constant pressure at constant depth, dense rock under Earth's crust flows from below to even out the pressure, making the landscape rise. In addition, in a cold, polar climate like Antarctica, mountain peaks don't experience yearly thawing and refreezing, so they don't erode. This means that glacial activity in cold climates actually increases the difference in height between mountain peaks and valleys.
This effect is much more substantial than scientists believed, according to the new study by Tim Stern and colleagues of Victoria University in Wellington, New Zealand. Using the Transantarctic Mountains in western Antarctica as their model, the team assumed that most of the range's unusually sharp relief came from glacial erosion and used a computer model to reconstruct its original shape. By comparing before-and-after pictures, the researchers could estimate how much rock was scooped away by glaciers and the amount the earth must have rebounded upwards to compensate for this. The findings indicate that the rebound was gigantic, accounting for up to 50% of the range's height. Because similar climates existed in North America and Europe during the Ice Ages, glacial erosion may have also significantly contributed to mountain height on these continents, report the researchers in this month's issue of Geology.
It's a "very nice" analysis, says Peter Molnar, a geophysicist at the University of Colorado, Boulder. "They've shown how big the effect [of climate] can be if you look at an extreme case."