Toba, the Earth's largest Quaternary caldera, is seen here in a false-color satellite image. The 35 x 100 km caldera, partially filled by Lake Toba, was formed during four major ignimbrite-forming eruptions in the Pleistocene, the latest of which occurred about 74,000 years ago. The large island of Samosir is a resurgent uplifted block. The solfatarically active Pusukbukit volcano was later constructed near the south-central caldera rim, and Tandukbenua volcano on the NW rim may be only a few hundred years old. Landsat image, 1987 (National Aeronautical and Space Administration/EOSAT).
The 35 x 100 km wide Toba caldera, partially filled by waters of Sumatra's Lake Toba, is Earth's largest Quaternary caldera. This view looks west toward the northern end of Samosir Island, which is part of a massive inclined block uplifted after eruption of the Young Toba Tuff (YTT) about 74,000 years ago. The island, once entirely covered by Lake Toba, is formed of caldera-fill deposits of YTT capped by lake sediments.