drew my attention to a marvellous satellite image that NASA's Earth Observatory
published in 2009.
Please note that north is to the right. The image shows the Tao-Rusyr Caldera at the southern end of Onekotan Island, Kuril Islands, Russia. The 7.5 km wide caldera was formed during an explosive eruption less than 10,000 years ago (reported ages range from 5550 to 9400 Before Present). The waters of Kal'tsevoe Lake fill the caldera, along with a large symmetrical andesitic cone, Krenitsyn Peak, that rises as an island within the lake. This volcano was named after Captain Pyotr Krenitsyn of the Imperial Russian Navy. The most recent, and only historical eruption, in 1952, formed a small lava dome on the island's east coast. Krenitsyn Peak has a summit crater 350 m wide and is the highest point (1,325 m) of the volcano and on the entire Onekotan Island. Another caldera, Nemo Peak
, lies at the northern end of the island, and it also contains a central cone and crater lake. A relatively flat isthmus connects the two stratovolcanoes, Krenitsyn and Nemo.
I think I also owe you an image (from NOAA
) of the Tao-Rusyr Caldera from the ground:
Onekotan (Russian: Онекотан) is an uninhabited volcanic island located near the northern end of the Kuril Islands chain in the Sea of Okhotsk in the northwest Pacific Ocean. Its name is derived from the Ainu language for "large village". Onekotan is roughly rectangular, with a length of 42.5 km, and a width ranging from 11 km to 17 km. It has an area of 425 km².
The Kuril Islands is a volcanic island arc that stretches approximately 1,300 km northeast from Hokkaidō, Japan, to Kamchatka, Russia, separating the Sea of Okhotsk from the North Pacific Ocean. The volcanic arc continues in the Kamchatkan Peninsula which is famous for its many volcanoes. The Kurils count 56 islands and many more minor rocks. All of the islands are now under Russian jurisdiction, but Japan claims the four southernmost as part of its territory (occupied by Russia since World War II). Below is a map of the islands showing the de facto division between Japan and Russia over time (Image from Wikipedia).
The Kuril Island volcanoes are fueled by magma generated by the subduction of the Pacific Plate under the Eurasian Plate, which takes place along a deep trench about 200 km to the islands' east. Large earthquakes at the Kuril Trench may lead to tsunamis. The 1952 Severo-Kurilsk Tsunami was a major tsunami that hit Severo-Kurilsk on the (larger) island of Paramushir north of the Onekotan Island. It occurred on 5 November 1952 at about 5 a.m. It led to the destruction of many settlements in Sakhalin Oblast and Kamchatka Oblast, while the main impact struck the town of Severo-Kurilsk (See google map below). The tsunami was generated by a major earthquake in the Pacific Ocean, 130 km from the shore of Kamchatka, with an estimated magnitude of 8.5. There were three waves about 15-18 m high.
Finally a google map with Onekotan, Severo-Kurilsk on Paramushir, and the Kuril Trench (Dark blue):
and my marking of the location of the two calderas/volcanoes on Onekotan island: