Lake Toba
Volcanic activity in the Toba Caldera was marked by effusive eruptions that occurred around 1.3 million years ago, centered around Haranggaol, resulting in the formation of Haranggaol Andesitic Lava rocks.
The volcanic activity continued with explosive eruptions that occurred 1.2 million years ago in the same area (around Haranggaol), resulting in the formation of Haranggaol Dacitic Tuff (HDT).
The center of the eruption shifted to the south, around the Porsea region, 850,000 years ago, resulting in an explosive eruption that produced 500 km3 of pyroclastic material with a composition ranging from dacite to rhyolite.
The eruption center shifted back to the north in the Haranggaol region 501,000 years ago, resulting in an explosive eruption that spewed 60 km3 of rhyolite.
The Formation of the Toba Caldera and Samosir Island
The eruption of a Supervolcano occured 74,000 years ago, ejecting 2,800km3 of pyroclastic material ranging in composition from dacite to rhyolite, and leaving behind a trace in the form of Toba Caldera with an area of 100 km x 30 km.
Post-calderic activity of the Supervolcano caldera is indicated by the appearance of the volcanic cones along the western and eastern sides of the caldera, accompanied by resurgence doming. In addition to the resurgent dome, there was also volcanic activity on the western and eastern sides of the caldera.
West side growth
- 64,000 - 56,000 years ago: Mount Sibandang - Pardepur
- 55,000 - 46,000 years ago: Mount Pusuk Buhit and Mount Sipisopiso
East Side growth
- 69,000 - 65,000 years ago: Tuktuk Lava Dome Complex, Samosir Lava Dome, Sibatunatu-Simanindo Hills
Resurgent Doming and The Formation of Samosir Island
Volcanic activity continues from the magma chamber, causing pressure and uplift of the caldera floor, resulting in the emergence of Samosir Island on the surface of the lake (at an altitude of 900 meters above sea level) for 33,000 years, and this process is still ongoing.
Currently, the highest point of Samosir Island is at an elevation of 1,600 meters above sea level, with the uplift intensity gradually decreasing, moving towards a new equilibrium.
Toba Caldera's Anatomy
Caldera comes from the Spanish word meaning "frying pan". It is a giant crater formed by the collapse of the roof of a magma chamber following an explosive eruption. A plateau is a flat highland
Samosir Island
Traces of the collapse of the caldera wall
Caldera wall
Plateau
Waterfall
Lake Toba is the largest freshwater volcanic lake in the world
With a size of 100 km x 30 km, it is estimated that it took 1,500 years for rainfall to fill Lake Toba with 240 km3 of water as we see it today.
Lake Toba holds water from around 280 rivers and over 100 waterfalls.
The world experienced great destruction when the Toba Supervolcano erupted 74,000 years ago. Over the years, the earth has been beset by extreme weather and darkness, causing mass extinctions and forcing surviving prehistoric humans to live in extremely harsh conditions.
Although the disaster left deep scars on Earth, life eventually recovered. Humans managed to survive and thrive amidst the memory of the legendary Toba Supervolcano eruption.
