Walter G. Allgöwer imageBROKER/Newscom

Angkor temples are safe from sudden collapse—for now

For years, scientists working at the Cambodian temple Angkor Wat have imagined a nightmare scenario: Tourists becoming trapped as the 12th century Khmer edifice, made of sandstone bricks, collapses around them. Each year, 3 million people visit the Angkor archaeological site, which includes Angkor Wat and nearby sites like the Baphuon temple (above). And growing urban areas have robbed the region of groundwater, making scientists worry that such a collapse could be ever more likely. But until now, researchers had no idea how likely. Thick vegetation around the temples made it all but impossible to measure the subtle changes in earth and water that could presage a tragedy. To get around the problem, a team of researchers has used radar images from two satellites, which can essentially see through the forest to the ground below. By comparing the images, they could see shifts in the ground under Angkor, as well as in the monuments themselves, as small as 1 millimeter. After looking at dozens of images, their news is good: The monuments moved by less than 3 millimeters a year between 2011 and 2013, suggesting that groundwater pumping hadn’t significantly destabilized them, they report today in Science Advances. Still, risks remain, because groundwater levels fluctuate naturally between the wet and dry seasons. If climate change extends future dry seasons, depleting groundwater in the Angkor region, the site may be in for much more danger than that caused by local pumps.