UN Security Council sanctions aside, one of the reasons China has closed much of its border with North Korea and imposed emergency measures to monitor radiation flowing across the mountainous terrain is because the country’s scientists worry that the mountain under which North Korea has held five of its six nuclear tests is in danger of collapsing and unleashing a devastating cloud of radiation on the surrounding terrain.
And just in case anybody doubted the veracity of China’s warnings, a slew of independent analysts have confirmed what Beijing has long feared: North Korea’s Mount Mantap, a 7,200-foot-peak under which North Korea has carried out most of its recent nuclear tests, is suffering from “tired mountain syndrome,” according to the Washington Post.
Satellite images captured during the North’s Sept. 3 test of a purported hydrogen bomb, Mt Mantap could be seen visibly shifting during the enormous detonation which triggered a 6.3 magnitude earthquake in North Korea’s northeast.
And since that test, the region - which is not known for seismic activity - has experienced several landslides and no fewer than three more earthquakes.'
The North, which carried out its first nuclear test more than ten years ago in 2006, has built a complex system of tunnels underneath the mountain that’s known as the Punggye-ri Nuclear Test Facility. According to WaPo, intelligence analysts use satellites to monitor the three known entrances to Punggye-ri to try and anticipate when another test might be coming.
Arms Control Wonk describes the site in more precise detail.
North Korea’s nuclear test site comprises a number of tunnel complexes in mountains surrounding a main support area. Following an initial nuclear explosion in 2006, subsequent nuclear tests have been conducted in a tunnel complex to the North of the support area, under Mt. Mantap. The site contains additional tunnel complexes that may be suitable for nuclear explosions to the south and west of the support area. The Punggye-ri site is capable of hosting nuclear explosions in tunnels with yields of up to a few hundred kilotons.
The tremors unleashed by the North’s last test shook homes in northeastern China. And eight minutes after the initial quake subsided, there was a 4.1-magnitude earthquake that appeared to be a tunnel collapsing at the site.
Images captured by Airbus showed the mountain trembling during the test. An 85-acre area on the peak of Mount Mantap visibly subsided during the explosion, an indication of both the size of the blast and the weakness of the mountain.
Anybody who was around in the 1950s and 1960s will remember that “tired mountain syndrome” was a diagnosis last applied to the Soviet Union’s atomic test sites. To be sure, earthquakes also occurred at the US nuclear test site in Nevada after detonations there.
“The underground detonation of nuclear explosions considerably alters the properties of the rock mass,” Vitaly V. Adushkin and William Leith wrote in a report on the Soviet tests for the United States Geological Survey in 2001. This leads to fracturing and rocks breaking, and changes along tectonic faults.
Analysts Frank V. Pabian and Jack Liu worry that the blasts have caused substantial damage to the North’s tunnel network.
“Based on the severity of the initial blast, the post-test tremors, and the extent of observable surface disturbances, we have to assume that there must have been substantial damage to the existing tunnel network under Mount Mantap,” they wrote in a report for the specialist North Korea website 38 North.
Of course, just because the mountain is literally crumbling doesn’t mean the North will stop using it as a test site. As WaPo notes, the US didn’t abandon the Nevada test site after earthquakes there, they said. Instead, the US kept using the site until a nuclear test moratorium took effect in 1992. For that reason, analysts will continue to keep a close eye on the Punggye-ri test site to see if North Korea starts excavating there again — a sign of possible preparations for another test.
But as Chinese scientists have warned, one more test might be one too many.
Chinese scientists have warned that another test under the mountain could lead to an environmental disaster. If the whole mountain caved in on itself, radiation could escape and drift across the region, said Wang Naiyan, the former chairman of the China Nuclear Society and senior researcher on China’s nuclear weapons program.
“We call it ‘taking the roof off.’ If the mountain collapses and the hole is exposed, it will let out many bad things,” Wang told the South China Morning Post last month.
But perhaps equally as concerning as the collapse of Mantap is the possibility that another test could trigger an eruption at Mt. Paektu, an active supervolcano located on the North Korea-China border, about 80 miles from Pyungge-ri.
The mountain has not experienced a major eruption for centuries, and its last small rumble was in 1903. But an eruption could have devastating consequences - possibly causing more death and destruction than a nuclear blast.
And with a North Korean diplomat reiterating today that the North intends to continue with its nuclear program, while the country has also decried the military exercises happening in the waters east of the peninsula, where the USS Ronald Reagan is conducting training drills with the South Korean navy.
However, the North’s Oct. 10 holiday and the Oct. 18 beginning of China’s National Party Congress having come and gone without a new test. And signs of movement at some of the country’s missile test sites spotted in recent weeks have apparently been false alarms.
But given the amount of time that has elapsed since the North’s most recent missile test, it’s likely that the next provocative test - be it a test of a new long-range missile or a seventh nuclear test - isn’t too far off.