Tao-Rusyr Caldera is a stratovolcano

Stratovolcano

A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...

 located at the southern end of Onekotan

Onekotan

Onekotan Island 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".-Geology:...

 Island, Kuril Islands

Kuril Islands

The Kuril Islands , in Russia's Sakhalin Oblast region, form a volcanic archipelago that stretches approximately northeast from Hokkaidō, Japan, to Kamchatka, Russia, separating the Sea of Okhotsk from the North Pacific Ocean. There are 56 islands and many more minor rocks. It consists of Greater...

, Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. It has 7.5 km wide caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 formed during a catastrophic eruption less than 10,000 years ago (reported ages range from 5550 to 9400 Before Present

Before Present

Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

). The waters of Kal'tsevoe Lake fill the caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

, along with a large symmetrical andesitic

Andesite

Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...

 cone, Krenitsyn Peak, that rises as an island within the lake. This volcano was named after Captain Pyotr Krenitsyn

Pyotr Krenitsyn

Pyotr Kuzmich Krenitsyn , spelt "Krenitzin" in the United States, was a Russian explorer and Captain/Lieutenant of the Imperial Russian Navy. Following Vitus Bering's 1741 tragic venture he was the first to conduct an expedition to Alaska and the Aleutians...

 of the Imperial Russian Navy

Imperial Russian Navy

The Imperial Russian Navy refers to the Tsarist fleets prior to the February Revolution.-First Romanovs:Under Tsar Mikhail Feodorovich, construction of the first three-masted ship, actually built within Russia, was completed in 1636. It was built in Balakhna by Danish shipbuilders from Holstein...

.

The most recent eruption, in 1952, formed a small lava dome on the island's coast. Krenitsyn Peak has a summit crater 350 m wide and is the highest point of the volcano and on the entire Onekotan Island. Another caldera, Nemo Peak

Nemo Peak

Nemo Peak is a stratovolcano located at the northern end of Onekotan Island, Kuril Islands, Russia. It is truncated by two nested calderas, with the cone of Nemo Peak itself rising in the southwest end of the youngest caldera and a crescent-shaped crater lake partially filling the northeast part....

, lies at the northern end of the island, and it also contains a central cone and crater lake.