Lvinaya Past is a volcano located in the southern part of Iturup

Iturup

Iturup is the largest island of the South Kuril Islands. It is the northernmost island in the southern Kuril/Chishima islands, and though it is presently controlled by Russia, Japan also claims this island...

 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...

. The volcano derives its name from a rock resembling a sleeping lion that breaches the surface at the center of the submerged caldera rim. A shallow 5-km-wide passageway on the NW side allows access of the Sea of Okhotsk

Sea of Okhotsk

The Sea of Okhotsk is a marginal sea of the western Pacific Ocean, lying between the Kamchatka Peninsula on the east, the Kuril Islands on the southeast, the island of Hokkaidō to the far south, the island of Sakhalin along the west, and a long stretch of eastern Siberian coast along the west and...

 into the caldera basin, whose floor is 550 m below sea level and lies almost 1 km below the caldera rim.

The caldera formed about 9400 years (7480 BC ± 50) ago during one of the largest Holocene eruptions of the Kuril Islands. Between 70 and 80 cubic kilometers of tephra was erupted, measuring a Volcanic Explosivity Index

Volcanic Explosivity Index

The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....

 of 6. Thick dacitic pumice deposits from this eruption form the 50–60 m high Yuzhny (Southern) isthmus, which joins the three southernmost volcanoes on Iturup Island, Rokko, Lvinaya Past, and Berutarube. This was the only Holocene

Holocene

The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

eruption from the caldera.