E-san (恵山（えさん） in Japanese) is the southernmost active volcano on Hokkaido. It is a small andesitic stratovolcano located in the southeast of the Kameda-hanto Peninsula extending into the Pacific Ocean from the south of Hokkaido across the Tsugaru Strait from Honshu. It has a lava dome forming its summit and another lava dome to the NW. Both have been active within the past 10,000 years, the summit lava dome forming about 9000 years ago. The only known historic eruptions were a small phreatic eruption in 1846 which produced a lahar with many fatalities, and a small explosion in 1874. E-san has many active fumaroles in a thermal area on the upper NW flank. Fumaroles are located on the upper NW flank. At the foot of Mt. E-san is the Esan-onsen Hot Spring, a popular attraction since the latter half of the 19th century, it is renowned for its distinctive wine-red colored water.

E-san volcano Hot Springs

Hot springs are found in 2 areas separated by the River Yaziri. The most well-known and active area are the Mizunashi hot springs east of E-san volcano.

The following is summarized from John Seach, who quotes from an unknown source:

The Mizunashi hot springs are artesian springs of an aquifer in porous liparitic andesite. The Mizunashi hot springs can be divieded into a northern and southern part, the springs in the southern part being more active. Their maximum temperature reaches 52.4°C at the coast.

There is little influence of sea water on the chemical composition on the hot springs at low tide.

During drilling, temperatures of > 47°C were observed under the ground at 35 m depth below sea level, at a distance of 50 m from the Mizunashi coast.



Sources

- Smithsonian / GVP volcano information

- Japan National Tourism Organization

- link www.volcanolive.com/esan.html>John Seach, E-san volcano information