|Sheehan Home | People | Projects | Publications | Teaching/Classes | Photo Galleries | Contact|
|RESEARCH GROUPS @ CIRES >|
Rio Grande Rift F.A.Q.
Measuring Rio Grande Rift Crustal Deformation
Please note that this page is from 2006 and is not up-to-date.
What is the Rio Grande Rift? A rift is a thinning in the Earth's surface caused by stretching the surface through geological stress. It was initially formed between 35 and 29 million years ago when the crust began to spread apart, triggering volcanism in the region. The Rio Grande Rift runs south to north from the state of Chihuahua, Mexico to Leadville, Colorado and perhaps even further north.
Some rifts, such as the Basin and Range Province further west, are at higher elevation than their surroundings. Others, such as the Rio Grande, form basins (above) that, over thousands and millions of years, fill with sediments. At Albuquerque, NM, the basin sediments are three miles deep. The rift continues to widen today, although very slowly. The graphic to the right from the USGS shows the primary basins of the rift.
Where are there other rifts in the world? Most rifts are found along mid-ocean ridges. Only a few are located on land, such as the East African rift or Great Rift and Lake Baikal, a lake-filled rift in Russia. While ocean rifts are often caused by divergent plate boundaries, continental rifts such as the Rio Grande are referred to as "extentional tectonics" caused by the buoyancy of rocks deep below.
Is there a risk of earthquakes in or around the Rio Grande Rift? Seismic activity associated with earthquakes is considered to be low to moderate in New Mexico and Colorado, with a slightly higher risk in and around the rift region, but there are still many unknowns about the risks of the rift that require further study. There is geologic evidence that large earthquakes (7.0 to 7.3 magnitude) have occurred in south-central Colorado within the past 5,000 to 15,000 years. While statistically less likely to have large-scale seismic activity than regions such as the San Andreas Fault in California, a large earthquake (7.0 magnitude or larger) will occur at some point in the future.
Could there by volcanoes around the Rift? Intense volcanism (volcanic activity) has occurred in the region beginning at the onset of rifting millions of years ago. For example, Valles Caldera near modern day Los Alamos, NM, one of the world's largest and youngest calderas, was created 1.2 million years ago through the collapse of a magma chamber. Volcanism is considered by geologists to be dormant, not extinct, in the rift region.
Did the Rio Grande River create the Rift? No. Following the path of least resistance, the waters of today's Rio Grande river flows from its headwaters in southern Colorado through New Mexico following the pre-established rift valley before turning east along what is now the border of the US and Mexico and into the Gulf of Mexico.
How are scientists studying the Rio Grande Rift? Since the movements of the rift are small and slow (between 0.5 and 2 millimeters per year,) scientists are testing a new technology to see whether it can tell them more about the rift. A team of scientists from the University of Colorado and the University of New Mexico with funding from the National Science Foundation's Earthscope program are seeking information on how much the Rio Grande Rift is moving by setting global positioning systems (GPS) to fixed geologic features in a grid system that runs from the central Colorado Rockies into southern New Mexico. The team is seeking to determine whether GPS instruments, which rely on satellites for their measurements, can accurately measure the miniscule movements of the Rio Grande Rift. Questions addressed by this research include: