Seeing Sierra Nevada uplift from space topic of Lake Tahoe science lecture

Scientific evidence from the University of Nevada, Reno shows the entire Sierra Nevada mountain range is rising at the relatively fast rate of 1 to 2 millimeters every year.
A lecture on Tuesday, Sept. 11 will provide this new information on Sierra Nevada uplift as seen from space. The lecture, by Bill Hammond, associate professor at the University of Nevada at Reno, will be at the Lake Tahoe Center for Environmental Sciences, 291 County Club Drive, in Incline Village.
Modern space geodesy has recently enabled the direct observation of slow geological processes that move and shape Earth’s surface, including plate tectonics and crustal strain accumulation that leads to earthquakes.

More elusive has been the direct observation of active mountain growth, because GPS measurements have larger uncertainties in the vertical direction and mountain growth is typically very slow.
The latest research using high-precision technologies indicates a relatively high vertical uplift rate for the Sierra Nevada, between 1 and 2 mm/yr. Thus the modern Sierra Nevada uplift is still very active and consistent with theories that call for a relatively young mountain range.
"The exciting thing is we can watch the range growing in real time,” Hammond said in a UNR interview earlier this year. “Using data back to before 2000 we can see it with accuracy better than 1 millimeter per year. Perhaps even more amazing is that these miniscule changes are measured using satellites in space.”
Miniscule as they may be, the data indicate that long-term trends in crustal uplift suggest the modern Sierra could be formed in less than 3 million years, which is relatively quick when compared to estimates using some geological techniques.
Hammond and his colleagues in the University’s Nevada Geodetic Laboratory and University of Glasgow use satellite-based GPS data and InSAR (space-based radar) data to calculate the movements to this unprecedented accuracy. The calculations show that the crust moves upward compared to Earth’s center of mass and compared to relatively stable eastern Nevada.
The data may help resolve an active debate regarding the age of the modern Sierra Nevada of California and Nevada in the western United States. The history of elevation is complex, exhibiting features of both ancient (40–60 million years) and relatively young (less than 3 million years) elevation. The “young” elevation is the uplift Hammond and colleagues have tracked.
“The Sierra Nevada uplift process is fairly unique on Earth and not well understood.” Hammond said. “Our data indicate that uplift is distributed along the entire length of the 400-mile-long range, between 35 and 40 degrees north latitude, that it is active, and could have generated the entire range is less than 3 million years, which is young compared to estimates based on some other techniques. It basically means that the latest pulse of uplift is still ongoing.”
Possibly contributing to the rapid uplift is the tectonic extension in Nevada and a response to flow in the mantle. Seismologists indicate the mountain range may have risen when a fragment of lower plate peeled off the bottom of the lithosphere allowing the “speedy” uplift, like a ship that has lost its keel. In comparison, other ranges, such as the Alps or Andes, are being formed in an entirely different process caused by contraction as two plates collide.
Hammond studies active deformation and dynamics of the Earth using space-based geodetic techniques. He works in the Nevada Geodetic Laboratory, which is a part of the Nevada Bureau of Mines and Geology in the University’s College of Science. His previous employment includes four years at the U.S. Geological Survey in Menlo Park, CA. He earned his Bachelor’s degree in mathematics at U.C. Berkeley and his Ph.D. in geophysics at the University of Oregon, Eugene. He and his family enjoy the Sierra Nevada scenery while living in Truckee. Find more information about Bill, links to publications, courses, go here.