#kuttara

From NASA Earth Observatory Image of the Day; September 26, 2018:

Volcanic Hell Makes for Bathing Heaven

The last big eruption at Hokkaido’s Kuttara volcano happened roughly 40,000 years ago, about the time Neanderthals were going extinct and a bit before people had begun to domesticate dogs.

Earlier eruptions at the Japanese stratovolcano had produced thick andesitic lavas that flowed into two large tongue-shaped lobes immediately north of the volcano. Silica-rich, viscous magma blocked the vent, so pressure built up in much the same way it does in a soda bottle after it is shaken. When the pressure grew intense enough, it blasted a vent at the top of the volcano and sent a large plume of ash shooting into the air. Fast-moving jumbles of ash, gas, and other debris—known as pyroclastic flows—swept down the southwestern slope of the volcano.

That explosive eruption—and the slumping of rock into the emptied-out lava chamber—sculpted the bowl-shaped caldera that now sits at the top of the mountain and holds Lake Kuttara, one of the roundest and clearest lakes in Japan. The Operational Land Imager(OLI) on Landsat 8 acquired an image on September 15, 2015. For the three-dimensional view, the Landsat 8 image was draped over a global digital elevation model built from data acquired by NASA’s Shuttle Radar Topography Mission.