The Sierra had a growth spurt, gaining inch at height of drought

Paola Ditto
Dicembre 14, 2017

According to NASA scientists, it is possible to grow an inch or more in height just by displacing water weight. The caveat: It only works if you're an actual mountain. The culprit was huge amounts of water draining out of the mountain's rocks and soil, and into the Earth below.

"This suggests that the solid Earth has a greater capacity to store water than previously thought", Donald Argus, a JPL research and lead author of the study, said in a statement. The team's findings were recently published in the Journal of Geophysical Research: Solid Earth. It also indicates that in the following two years of more abundant snow and rainfall the mountains have also fallen about a half-inch in height while regaining about half as much water in the rock as they had lost in the preceding drought.

The scientists reasoned that the Earth's surface sinks when it is weighed down with water and rebounds when the water evaporates or is otherwise lost. There are a number of factors at play with how mountains moved, but the NASA team accounted for tectonic plates, volcanic activity, and high-and low-pressure weather systems while exclusively measuring the effects of water. However, calculations revealed that of the inch of observed uplift in the Sierras, only 0.2 inches (0.5 cm) could be attributed to groundwater pumping, and less than half of that came from tectonic shifts.

The study by NASA's Jet Propulsion Laboratory in Pasadena, California, found that the mountain range rose almost 2.5 centimeters in height from October 2011 to October 2015, when the state experienced its most extended drought. From 2011 to 2015, at the height of the drought, the mountain range raised itself by a full inch.

The team found that the amount of water lost from within fractured mountain rock in 2011-2015 amounted to 10.8 cubic miles of water.

Famiglietti hopes the study will prod scientists to further look at water trapped within mountains. As mountains are relieved of their water weight, they undergo a process called elastic rebound and slowly rise back to their original elevation before the water pressed them down.

"One of the major unknowns in mountain hydrology is what happens below the soil", says JPL water scientist Jay Famiglietti, who worked on the study. While the water is inaccessible to humans, it is equivalent to 45 times as much water as the city of Los Angeles uses in a year.

The water displaced by the mountains drains too deeply to be accessible.However, the techniques used to analyze water loss and elevation in this study pave the way to a more accurate understanding of mountain groundwater's impacts, the researchers said.

Researchers used 1,300 Global Positioning System stations throughout the mountain range to closely observe how its elevation changed during the drought.

'Is there a significant amount of groundwater stored within mountains? "This is one of the key topics that we addressed in our study".

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