Raindrops reveal how a wave of mountains moved south across the country

ScienceDaily (2010-12-21) -- Analyzing the isotope ratios of ancient raindrops preserved in soils and lake sediments, researchers have shown that a wave of mountain building began in British Columbia, Canada about 49 million years ago and rolled south to Mexico. The finding helps put to rest the idea that there was once a Tibet-like plateau across the western US that collapsed and eroded into the mountains we see today.