Tondano volcan

Tondano is a large, ca. 20 x 30 km wide lake-filled caldera in north Sulawesi and famous for its idyllic landscape.

Introduction:

The caldera was formed perhaps as much as several million years ago. Younger cones are present in the caldera, as well as obsidian flows, and thermal areas. Lake Tondano lies adjacent the well-defined eastern caldera rim.
The active andesitic-to-basaltic stratovolcanoes Soputan, Sempu, Lokon-Empung and Mahawu have formed on the poorly defined southern and northern rims of the caldera.
The age of the latest eruptions within the caldera is not known, although thermal areas occur at Batu Kolok and Sarangson, and at the Tampusu cinder cone and Lahendong maar.
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Source: GVP