Rio Grande Rift FAQ

Measuring Rio Grande Rift Crustal Deformation

A joint project of:

Contents:
  1. What is the Rio Grande Rift?
  2. Where are there other rifts in the world?
  3. Is there a risk of earthquakes in or around the Rio Grande Rift?
  4. Could there be volcanoes around the rift?
  5. Did the Rio Grande River create the rift?
  6. How are scientists studying the Rio Grande Rift?
  7. How can I learn more?
  8. What will each GPS station look like?
  9. How will data be collected?

What is the Rio Grande Rift?

A rift is a surface feature characterized by an elongated valley. Rifts are created when Earth’s crust stretches and thins. The Rio Grande Rift began forming between 35 and 29 million years ago when Earth’s crust began to spread apart, triggering volcanism (volcanic activity) in the region. It runs south to north from the state of Chihuahua, Mexico, to Leadville, Colorado, and probably even further north. Rifts like the Rio Grande form basins (topographic depressions) that fill with sediments over millions of years. In Albuquerque, New Mexico, the basin sediments are three miles thick. The Rio Grande Rift continues to widen today very slowly.

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Depiction of a cross-section of a rift. Image courtesy of the USGS.

Map of Rio Grande Rift region (above) showing the primary basins of the rift. Image courtesy of the USGS.

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 Rio Grande Rift, East African Rift (sometimes referred to as the Great Rift) and Lake Baikal, a lake-filled rift in Russia. Oceanic rifts are typically found at divergent plate boundaries, where plates are moving apart. In contrast, continental rifts such as the Rio Grande are not located at plate boundaries. These continental rifts form in “extensional tectonic” settings in which Earth’s crust thins and weakens due to the rising of hot rock deep below the surface.

Is there a risk of earthquakes in or around the Rio Grande Rift?

There is geologic evidence that multiple major earthquakes (7.0 to 7.5 magnitude) have occurred in Colorado and New Mexico within the past 15,000 years. Although it is 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 in the Rio Grande Rift area at some point in the future. Throughout New Mexico and Colorado as a whole, seismic activity associated with earthquakes is considered to be low to moderate, with a slightly higher risk in and around the rift region. However less is known about seismic risk here than in most of the rest of the western U.S. There's more information on Rio Grande Rift seismic hazard here.

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Could there be volcanoes around the rift?

Intense volcanism has occurred in the region since the onset of rifting millions of years ago. For example, Valles Caldera near modern-day Los Alamos, New Mexico, is one of the world's largest and youngest calderas. It was created 1.2 million years ago following the collapse of a magma chamber. Geologists consider the volcanic features in the rift region to be dormant, not extinct.

Did the Rio Grande River create the rift?

No. The Rio Grande Rift was formed by extension of Earth’s crust. Crustal thinning and normal faulting associated with the rifting process formed topographic depressions that captured drainages, formed basins and gradually directed drainage along the rift axis. As water progressively incised (cut through) the rocks, a river formed. Today's Rio Grande River flows from its headwaters in southern Colorado through New Mexico along the route established by tectonic rifting before turning east along what is now the border of the United States and Mexico, and then into the Gulf of Mexico.

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Rio Grande River near Taos, New Mexico. Image courtesy of the Bureau of Land Management.

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 using a new technology to find out more about the rift.

A team of scientists from the University of Colorado, University of New Mexico and Utah State University, with funding from the National Science Foundation's EarthScope Program, are collecting data on how the Rio Grande Rift is moving by setting global positioning system (GPS) instruments in a grid 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:

  • What seismic hazard does the Rio Grande Rift pose?
  • How wide is the rift, and how does the amount and rate of deformation vary along the rift from north to south?
  • How far north has the Rio Grande Rift propagated? (How far north does crustal extension associated with the Rio Grande Rift occur?)

How can I learn more?

For an education kit about rifts in general and the Rio Grande Rift in particular, contact Mark McCaffrey. There is also more information about the project and its objectives at the Rio Grande Rift main page.

Site locations in the Rio Grande Rift GPS network are shown as triangles; the red triangles are already installed and collecting data. Plate Boundary Observatory stations are shown as stars. Blue stars are installed, purple stars are planned. Locations of other GPS network sites are shown as blue circles.

Rio Grande Rift GPS station at Great Sand Dunes National Park. Photo courtesy of UNAVCO.

What does a GPS station look like?

The stations have a steel tripod structure or a single steel mast that is drilled into bedrock and supports a GPS antenna. There is a steel box to house electronics and a small bank of solar panels.

How will data be collected?

A member of the project team will visit each station every three to six months (after the landowners have been notified) to download data and service the equipment. The stations will be operational about six years (until 2010 or 2011).

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An (outdated) pdf version of this faq is available here.