A large crater lake , called Heaven Lake , is in the caldera atop the mountain . The caldera was formed by the VEI 7 " Millennium " or " Tianchi " eruption of 946 , which erupted about of tephra . This was one of the largest and most violent eruptions in the last 5,000 years ( alongside the Minoan eruption , the Hatepe eruption of Lake Taupo in around AD 180 , the 1257 eruption of Mount Samalas near Mount Rinjani , and the 1815 eruption of Tambora )
Hatepe eruption
Hatepe eruption
Paektu Mountain