Indonesia: Lake Toba's Volcanic Underbelly 'Could Erupt at Any Time'
Geologists believe Mount Toba, which has erupted at fairly regular intervals over the last 1.2 million years, still poses a threat with its huge magma chamber and should be studied to assess the risk of a fresh eruption.Full Story
“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Nov 6, 2013
The old magma chambers are not a real problem as they have unroofed & exsolved gas, The result is a bloody great big hole in the ground with regrowth domes & stratovolcanoes along the rim such as Pusukbukit along the W. rim of Toba along the strike of the sumatra fault.
Fun bit comes from the new advancing magma chambers created by rise of a pluton from the partially melted crust overlying the magma disc under the Toba region. There IS one @ Toba forming the south Toba pluton extending as a series of thermal fields along the Sumatra fault from the S. rom of Toba through Tarutung and probably terminating NW of a thermal field on the flanks of the Pleistocene rhyolite stratovolcano SE. of Toba.
This advancing pluton alredy appears to have been responsible for the giant rhyolite pumice eruption in the S. Toba caldera lake as a result of a prior breakout through the great Sumatra fault. This appears to have been very similar to the inyo crater chain eruption of central California related to the Mono-Inyo supervolcano advancing pluton. In both cases the advancing pluton is too deep to unroof @ present in a catastrophic caldera forming eruption.
Keep watching that space.
Unlocking of the fault usually occurs during megathrust earthquakes involving relaxation of the overlying crust. The last was in the 1860s in this part of the world and no obvious eruptions occurred in the area @ the time. The pluton does however need to be high enough in the crust to enable a permanent connection from the magma chamber to the surface, which is a function of the depth & volatile content of the pluton. As an arc supervolcano, the South Toba pluton is likely to go kaboom before producing a surface dome cluster and may be only a few megathrust crustal relaxation events away, the event that causes the eruption would involve a bigger than average runout (they do vary).
When it goes kaboom, the sillar forming ash flow tuffs are likely to reach the coast at about the same time as the tsunami from the quake does. Will be interesting to watch from a distance.
Have a nice day: Ag
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