For millions of years, the Pacific and North American plates have been sliding past, and crashing into, one another. This ongoing conflict creates uplift, the geological phenomenon that formed mountains along the West Coast.

A new analysis by UC Santa Barbara earth scientist Alex Simms demonstrates that the Pacific coastlines of North America are not uplifting as rapidly as previously thought. The results appear in the journal Geological Society of America Bulletin.

"Current models overestimate uplift rates by an average of 40 percent," said Simms, an associate professor in UCSB?s Department of Earth Science. "They do not take into account glacio-isostatic adjustment, the Earth's response to the melting and growth of past ice sheets. Previous studies of the Pacific coast, including California, have ignored this when trying to use past sea levels to calculate uplift rates."