Soputan erupted from 24 May at 2243 until 26 May at 0300. An ash column rose to 4 km and moved W. Ash and sand-sized tephra fell on the area W of the volcano, forming a deposit >10 cm thick over ~75 km and 1-10 cm thick over an additional 125 km. Although there were no people within the danger zone, ~3,000 were in the alert zone. About 350 spontaneously evacuated from the area, where the primary cultivation is of coconut palms. Manado and Gorontalo airports (~50 km NNE and ~200 km SW of Soputan) were closed 26 and 27 May.

As of 30 May, no volcanic earthquakes had been recorded, although two tectonic events were detected. No premonitory activity was observed.

Geological Summary. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano is the only active cone in the Sempu-Soputan volcanic complex, which includes the Soputan caldera, Rindengan, and Manimporok (3.5 km ESE). Kawah Masem maar was formed in the W part of the caldera and contains a crater lake; sulfur has been extracted from fumarolic areas in the maar since 1938. Recent eruptions have originated at both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Information Contacts: A. Sudradjat, VSI.