Straddling the border of North Korea and China, sacred Mt Paektusan is a place of grand beauty and a symbol of unity for the two Koreas. But geologists worry that this sleeping behemoth may be overdue for an eruption like the magnitude-7 cataclysm that rocked East Asia a thousand years ago and plunged the world into darkness. This two-part series analyzes what might happen if such an event were to occur, while also looking in depth at other peoples who live in the shadow of active volcanoes.