17 December 2010

Colorado Plateau, stretching and breaking like a putty pancake

Posted by mohi

The Colorado Plateau. Image courtesy NPS

The Colorado Plateau, a tableland region of about 337,000 square kilometers that covers the Four Corners area of the American southwest, has been rotating ever so slightly around a point in the northern Rocky Mountains for millions of years. Its geological Lazy-Susan-esque action is credited with tearing a rift in the earth’s surface that now holds the waters of the Rio Grande.

But now the Colorado Plateau is doing something different. It appears to be stretching–expanding from east to west–crowding its neighboring landmasses on each side. And in time–many millions of years–the plateau will most likely stretch and break apart like a giant Silly Putty pancake.

At least, that’s what recent GPS data seems to indicate. The movement has been clocked at speeds ranging from 0.4 to 1.5 millimeters per year in different spots along the southwest and northeastern boundaries.

Corné Kreemer of the University of Nevada, Reno, Nevada, has been analyzing data from dozens of GPS stations scattered throughout the region, and he sees movement paired with seismic activity that indicates something else is going on besides the familiar old rotational twist that’s been happening for ages. He sees evidence of crinkling and deformation at the southwestern and northeastern corners of the plateau and increased earthquake activity that appears to be caused by tension created by the region’s expansion. The expansion is widest towards the southern half of the plateau and narrows towards the Plateau’s northern boundary.

Kreemer’s work has just begun, but he says that what he sees from the data so far convinces him that the plateau is indeed expanding. If you ask him if the Colorado Plateau is breaking up, he will answer with confidence in the affirmative. But he says he needs more GPS stations–especially along those active eastern and western boundaries–to get more details of the expansion. He adds that some of the stations have been in place for less than three years, and data sets covering longer periods of time will give him a better idea of how the trend may continue in the future.

–Donna Hesterman is a graduate student at the UC Santa Cruz science writing program.