PYONGYANG, North Korea (AP) — More than a thousand years ago, a huge volcano straddling the border between North Korea and China was the site of one of the biggest eruptions in human history, blanketing eastern Asia in its ash. But unlike other major volcanos around the world, the remote and politically sensitive Mount Paektu remains almost a complete mystery to foreign scientists who have — until recently — been unable to conduct on-site studies.

Fresh off their third visit to the volcano, two British scientists studying the mountain in an unprecedented joint project with North Korea say they may soon be able to reveal some secrets of the volcano, including its likelihood of erupting again. They’re collecting seismic data and studying rocks ejected in Paektu’s “millennium eruption” sometime in the 10th century.