Helatoba-Tarutung, located in northern Sumatra south of Lake Toba, is a group of sulfurous hot springs along a 40-km-long, NNW-SSE-trending stretch of the Renun-Toru fault zone.
Background:
Adjacent volcanics are of Pleistocene age (Aspden et al. 1982, Aldiss et al. 1983), but Helatoba-Tarutung was included in the Catalog of Active Volcanoes of the World (Neumann van Padang 1951) based on its geothermal activity.