A Louisiana sinkhole the size of 19 American football fields shifted sideways in radar measurements before its collapse and resulting evacuations in 2012, a study reveals.
The implication is that if certain types of radar measurements are collected regularly from above, it is possible to see some sinkholes before they collapse. The researchers added, however, that their discovery was “serendipitous” and there are no plans to immediately use a NASA robotic Gulfstream plane used for the study to fly over spots that could be vulnerable to sinkholes.
Data showed the ground near Bayou Corne moving horizontally up to 10.2 inches (26 centimeters) toward where the sinkhole appeared suddenly in August 2012. The hole started out at about 2 acres of size (1 hectare) — an area smaller than the initial ground movements — and now measures about 25 acres (10 hectares).
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The research was published in the journal Geology in February, and was first made available online in December. NASA highlighted the information in a press release published in early March.
“While horizontal surface deformations had not previously been considered a signature of sinkholes, the new study shows they can precede sinkhole formation well in advance,” stated Cathleen Jones, leader of the research and a part of NASA’s Jet Propulsion Laboratory in California.
“This kind of movement may be more common than previously thought, particularly in areas with loose soil near the surface.”
Jones and her NASA JPL colleague, Blom, found the information in NASA’s interferometric synthetic aperture radar (inSAR), which flew over the region in June 2011 and July 2012 on the agency’s Uninhabitated Aerial Vehicle Synthetic Aperture Radar. The radar can see shifts in the Earth’s surface.
The sinkhole — which is full of water and ground-up solids and is still getting bigger — collapsed after several small earthquakes and after the community became aware of “bubbling natural gas” in the area, NASA stated.
“It was caused by the collapse of a sidewall of an underground storage cavity connected to a nearby well operated by Texas Brine Company and owned by Occidental Petroleum,” the agency added.
“On-site investigation revealed the storage cavity, located more than 3,000 feet (914 meters) underground, had been mined closer to the edge of the subterranean Napoleonville salt dome than thought.” (A salt dome is a location in sedimentary rocks where salt is pushed up beneath the surface.)
Measurements of the area were taken as recently as October 2013, as the growing sinkhole is threatening the nearby community as well as a highway in the region.