From the story here:
The test turned the mountain into fragile fragments, the researchers found. ... The mountain’s surface had shown no visible damage after four underground nuclear tests before 2017. But the 100-kilotonne bomb that went off on September 3 vaporised surrounding rocks with unprecedented heat and opened a space that was up to 200 metres (656 feet) in diameter, according to a statement posted on the Wen team’s website on Monday.
