PVMBG reported that during June-3 July white plumes were observed rising as high as 750 m above Soputan even though inclement weather sometimes obscured crater views. Seismicity during the previous three months had declined (specifically shallow volcanic earthquakes, volcanic earthquakes, and signals indicating emissions and avalanches) but remained higher than levels recorded prior to the elevated activity which lead to the Alert Level increase on 26 December 2014. Low-frequency harmonic tremor was occasionally detected. The Alert Level was lowered to 2 (on a scale of 1-4). Residents and tourists were advised not to approach the craters within a radius of 4 km, or 6.5 km on the WSW flank.

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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)