Danau Toba II – Geology


  • Also called as Toba Caldera
  • Caldera is a volcanic feature usually formed by collapse of land following a volcanic eruption
  • This word is derived from Spanish/Latin word calderia which means ‘cooking pot’
  • It was formed during the Quaternary Period

Lake Toba, Landsat Satellite Image; Source – Wikipedia

  • This caldera consists of four overlapping volcanic craters that adjoin the Sumatran Volcanic Front
  • An estimate of 2,800 cubic kilometers of dense rock equivalent pyroclastic material, known as Young Toba Tuff was released during the eruption of this volcano
  • Tuff is a type of rock which consists of consolidated volcanic ash ejected from the vents during a volcanic eruption
  • After the eruption, a resurgent dome was formed between a new Caldera, joining two half domes by a longitudinal Graben
  • Graben is german for ditch and trench

Horst-Graben; Source – wikipedia.org

  • At least 4 volcanic cones and 3 craters are visible in the lake
  • Tandukbenua, one of the cones of Toba has only sparse vegetation, suggesting a young age of several hundred years
  • Also the Pusuk Buhit volcano is solfatarically (a.k.a fumeroll; means emits fumes, mixture of gasses) active and is a geological sanctuary
  • Pintau and Sibajak are the other two cones in this area

Pusuk Buhit; Source – Wikipedia


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