is an active volcano located in Shikotsu-Toya National Park

Shikotsu-Toya National Park

is a national park in the central part of the island of Hokkaidō, Japan. Named after the volcanic caldera lakes of Lake Shikotsu and Lake Tōya, it has a total area of 993.02 square kilometers...

 in Hokkaidō

Hokkaido

, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island; it is also the largest and northernmost of Japan's 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaido from Honshu, although the two islands are connected by the underwater railway Seikan Tunnel...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. It sits opposite Mount Tarumae

Mount Tarumae

is located in the Shikotsu-Toya National Park in Hokkaidō, Japan. It is located near both Tomakomai and Chitose towns and can be seen clearly from both. It is on the shores of Lake Shikotsu, a caldera lake. Tarumae is a 1,041 metre active andesitic stratovolcano, with a lava dome.-Eruptions:The...

 and Mount Fuppushi

Mount Fuppushi

is dormant volcano located in Shikotsu-Toya National Park in Hokkaidō, Japan. It sits adjacent to Mount Tarumae and opposite Mount Eniwa. Mount Fuppushi is on the south shore of Lake Shikotsu, the caldera lake that spawned the volcanoes.-References:*...

 on the shores of Lake Shikotsu

Lake Shikotsu

is a caldera lake in Chitose, Hokkaidō, Japan. It is a part of the Shikotsu-Toya National Park.- Geography :Lake Shikotsu is located in the south-west part of Hokkaidō. It has an average depth of and a maximum depth of , making it the second deepest lake in Japan, after Lake Tazawa...

, the caldera lake

Crater lake

A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...

 that spawned the volcanoes. Mount Eniwa is the tallest of the three volcanoes.

Eruptions

The last eruption occurred around the start of the 18th century (circa 1700 ±30 years). There are no historical records of this, but tephrochronology

Tephrochronology

250px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at the height of the [[volcanologists]] hands is [[rhyolitic]] [[tephra]] from [[Hekla]]....

 indicates phreatic

Phreatic

The term phreatic is used in Earth sciences to refer to matters relating to ground water below the water table . The term 'phreatic surface' indicates the location where the pore water pressure is under atmospheric conditions...

 explosions with mudflows

Lahar

A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley. The term is a shortened version of "berlahar" which originated in the Javanese language of...

 from crater 3. Two centuries before this eruption (circa 1550 ±75 years), radiocarbon dating

Radiocarbon dating

Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...

 indicates a similar eruption from crater 2. Around the same time (circa 1500 ±150 years), radiocarbon dating indicates another eruption, but from crater 1. This eruption included debris avalanches instead of mudflows. The oldest eruption that has been dated is an explosive eruption from the east side of the summit around 100 BCE ± 100 years according to radiocarbon dating. All these events were central vent eruptions with 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....

 (VEI) of 2.

Climbing Route

A single trail climbs the eastern side of the mountain. It gets progressively steeper as you climb. The trail starts in a forest about one 1 kilometre (0.621372736649807 mi) from Poropinai. The treeline is at about 800 metres (2,624.7 ft). From there the terrain is rocky and alpine. The climb takes 3-3.5 hours.

1972 Winter Olympics

In the 1972 Winter Olympics

1972 Winter Olympics

The 1972 Winter Olympics, officially known as the XI Olympic Winter Games, were a winter multi-sport event which was celebrated from February 3 to February 13, 1972 in Sapporo, Hokkaidō, Japan...

, Mount Eniwa was the site of the men's and women's downhill ski races

Alpine skiing at the 1972 Winter Olympics

Alpine skiing at the 1972 Winter Olympics consisted of six events, held near Sapporo, Japan, from February 5–13, 1972. The downhills were held at Mount Eniwa, and the four technical events at Teine.-Downhill:February 7, 1972...

. The course started at the summit and finished on the southwest slope.