The third phase of hot muddy ejection began on 25 July. Muddy water was carried 10 m above the [new crater that had formed on the E wall of the 1962 crater] when ejection began, but gradually declined. As of 1 November, water ejection had not been observed from the Volcano Observatory since 6 August. Figure 1 shows recently formed features at the E wall of the 1962 crater.

Figure 1. Sketch map of the E wall of the 1962 crater of Tokachidake on 7 June (top), and 25 June (bottom). Courtesy of JMA.

Further Reference. Miyakawa, H., Maekawa, T., and Yokoyama, I., 1986, Monitoring of the temperature by infrared thermometry at the crater wall of Tokachi volcano, Hokkaido: Geophysical Bulletin, Hokkaido University, v. 47, p. 17-31.

Geological Summary. Tokachidake volcano consists of a group of dominantly andesitic stratovolcanoes and lava domes arranged on a NE-SW line above a plateau of welded Pleistocene tuffs in central Hokkaido. Numerous explosion craters and cinder cones are located on the upper flanks of the small stratovolcanoes, with the youngest Holocene centers located at the NW end of the chain. Frequent historical eruptions, consisting mostly of mild-to-moderate phreatic explosions, have been recorded since the mid-19th century. Two larger eruptions occurred in 1926 and 1962. Partial cone collapse of the western flank during the 1926 eruption produced a disastrous debris avalanche and mudflow.

Information Contacts: JMA, Tokyo.