Satellite images taken before and after North Korea's last nuclear test beneath Mount Mantap show the mountain actually lost elevation. As the Washington Post reports, the depression of a 85-acre area—followed by three subsequent earthquakes over six weeks—shows not only the force of the Sept. 3 blast, but also the toll North Korea's nuclear program has taken on the 7,200-foot-tall mountain. It houses the tunnels that make up the Punggye-ri Nuclear Test Facility, which has been the site of each of North Korea's six nuclear tests since 2006. Chinese scientists warn further nuclear tests could trigger a collapse and the release of radiation. But though analysts at 38 North say Mount Mantap may be suffering from "tired mountain syndrome," they say North Korea is unlikely to abandon the site any time soon.
"Tired mountain syndrome" has previously been observed at other nuclear test sites in the US and Soviet Union. It essentially means a mountain is under such stress that the collapse of cavities or tunnels is possible. In North Korea's case, the Sept. 3 blast is likely to have caused "substantial damage to the existing tunnel network under Mount Mantap," analysts say. But as there are "two other, as yet unused tunnel complexes" at Punggye-ri, the analysts believe underground nuclear tests will likely continue. Indeed, CIA director Mike Pompeo tells the BBC that North Korea is "on the cusp" of developing a nuclear missile capable of reaching the US as it presses Australia to distance itself from the US in a letter published by the Sydney Morning Herald. (Read more North Korea stories.)