Hakoneyama volcano is truncated by two overlapping calderas, the largest of which is 10 x 11 km wide. The calderas were formed as a result of two major explosive eruptions about 180,000 and 49,000-60,000 years ago. Scenic Lake Ashi lies between the SW caldera wall and a half dozen post-caldera lava domes that were constructed along a NW-SE trend cutting through the center of the calderas. Dome growth occurred progressively to the NW, and the largest and youngest of these, Kamiyama, forms the high point. The calderas are breached to the east by the Hayakawa canyon. A phreatic explosion about 3000 years ago was followed by collapse of the NW side of Kamiyama, damming the Hayakawa valley and creating Lake Ashi. The latest magmatic eruptive activity about 2900 years ago produced a pyroclastic flow and a lava dome in the explosion crater, although phreatic eruptions took place as recently as the 12-13th centuries CE. Seismic swarms have occurred during the 20th century. Lake Ashi, along with the thermal areas in the caldera, is a popular resort destination SW of Tokyo.
Scenic Lake Ashi, seen here from the SE, occupies the SW corner of Hakone caldera. Hakone contains two calderas, the largest of which is 10 x 11 km wide. The arcuate caldera rim is at the left, and the slopes of a group of post-caldera cones form the right-hand shoreline. Post-caldera eruptions have constructed a half dozen lava domes along a SW-NE trend cutting through the center of the calderas. The latest eruption took place about 3000 years ago, although seismic swarms have occurred frequently during the 20th century.
Photo by Lee Siebert, 1963 (Smithsonian Institution).
Last updated 2019-10-29 05:30:02