Sierra getting "taller," scientists think they know why

Reported by: Terri Hendry
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Updated: 5/15/2014 8:11 pm
RENI, Nev. ( & KRNV) --For years scientists noticed the Sierra Nevada Mountain range was rapidly changing.  It was getting "taller," moving 1 to 3 millimeters each year.   New research unveiled this week by UNR scientists offers an explanation.  Professor Bill Hammond, Ph.D., with the Bureau of Mines in Geology in the College of Science at the University of Nevada, Reno said, "What's new is that we're seeing areas around the Great Valley rising up.  We now have linked that to the loss of underground water."

For more than a century, farmers in the Central Valley of California have been pumping underground water to irrigate their crops.  Hammond says over the years, farmers have pumped around 40 trillion gallons of groundwater.  Hammond said, "That's roughly equal to all the water in Lake Tahoe, the volume of which can cover the entire state of California in 14 inches of water."

He says scientists have been seeing small motions in their Global Positioning Satellite measurements for several years.  But until now, no one had an explanation. 

The findings also draw a relationship between the loss of groundwater and seismic activity along the San Andreas Fault.  He said, "The stress changes that result from the loading and unloading can effect the state of stress on the San Andreas fault."  But Hammond says scientists don't think this will result in a significant quake.  He said, "We don't think this is related to the occurence of very large earthquakes, it's the rate of very small earthquakes that we're talking about."

This newest research is being published in the scientific journal "Nature." Also, in April, University of Nevada, Reno Research Professor Geoff Blewitt unveiled the new findings in a presentation at the European Geophysical Sciences Union conference in Vienna, Austria.  

Hammond said one conclusion that can be drawn is that human activity can impact the Earth.  He said, "I think it's a very clear case where people in their coordinated actions, lots of them doing the same thing at the same time, is having a big impact on the Earth itself."  He said he hopes this leads to a better understanding of our environment and will spur further research.  

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oldguyincc - 5/16/2014 11:25 AM
0 Votes
That amount of water, at about eight pounds per gallon, weighs about 320,000,000,000,000 (three hundred twenty trillion) pounds, or one hundred sixty billion tons. That's enough weight to cause changes. Hammond didn't say that the water loss would cause earthquakes, he said it could shift the load. A shift of that much weight could cause tectonic movement. The water is largely lost because of evaporation. Watch the giant spray systems that the farmers use, and see why they require so much water. My GUESS is that 25% of the water used for irrigation is lost to evaporation.

kdavis52 - 5/16/2014 10:29 AM
0 Votes
I agree with RENOTRUTH. Any rain or snow should seep back and plate tectonics do play a role. Look at the Pacific Ring of Fire in the past 10 years. We've been bombarded with earthquake activity because of the plates moving so you would think that it would have cause and effect on any mountain range.

RENOTRUTH - 5/16/2014 9:51 AM
1 Vote
Wouldn't the underground water pumped out for irrigation drain back into the ground? Hammond said that its water that is permanently lost? The tetonic plates movement has nothing to do with the growth of the sierras?

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