Global Volcanism Program | Image GVP-06304
Sipisopiso waterfall, at the northern end of Lake Toba, formed on a cliff in the Middle Toba Tuff (MTT) deposit. The MTT rhyolite ignimbrite (more than 60 km3) was emplaced about 500,000 years ago during the third largest of the four major Toba caldera-forming eruptions. Products of the densely welded MTT eruption are distributed over the northern part of the caldera.
Photo by Bill Rose, 1982 (Michigan Technological University).