In this blog I talked about several catastrophic natural events, ranging from the terrifying eruption of Tambora volcano in 1815 , the possible future eruption of Marsili, passing through the 525-meter high tsunami el ' KT event that presumably lead to the extinction of the dinosaurs.
What I will talk about today is a catastrophic event that few have heard of, but that may have shaped human evolution and much of our planet: the Toba super-eruption of the volcano.
We are in Indonesia, in the northern island of Sumatra. Here is a lake, Toba, lungo 100 chilometri e largo circa 30, collocato ad un altezza di circa 900 metri dalla superficie del mare. Questo lago, in realtà, è anche un supervulcano: il bacino lacustre non è altro che un cratere causato da un'eruzione che si verificò tra 69.000 e 77.000 anni.
L'eruzione del vulcano Toba fu probablmente la più potente eruzione vulcanica mai verificatasi negli ultimi 25 milioni di anni. Questa eruzione catastrofica fu la terza di una serie di grandi eruzioni vulcaniche del Toba avvenute nell'ultimo milione di anni. La potenza fu tale che, sulla scala definita "Volcanic Explosivity Index", è stata classificata oltre il grado 8 (definito "mega colossal "). The Toba caldera is considered the elder sister of one of the Yellowstone.
If you read the post sull'eruzione of Tambora, know that quell'eruzione devastating stood at grade 7 of the VEI scale. The eruption of Toba
hurled into the air a volume of 2-3000 cubic kilometers of rock, 800 of them in the form of ash that was deposited over the entire South Asia, covering it with a thick layer, on average, 15 cm, with the regions (such as India and Malaysia) who were buried by layers of 6-9 meters thick.
were released into the atmosphere at least 6 billion tons of sulfur dioxide, and leave you to imagine the effects of this gas combined with water to tens of kilometers away from the eruption.
The lava flow emitted from the volcano covered an area of \u200b\u200b20 to 30,000 square kilometers with a layer of 50-150 meters of molten rock at 750 ° C (even with some areas covered by lava 400 meters of material). The surface temperature of the lava was reduced to about 100 ° C within a few days, but the mass of molten rock below the surface of the coldest high temperature maintained for a much longer period.
The eruption caused a drastic drop in temperatures across the planet: the global average temperature fell 3-5 degrees (with peaks of about 15 ° C reduction in Greenland two years after the event), and the Earth, which was already in a cooling period that lasted about 1000 years, cooled further, and the decrease of temperature was already in place accelerated.
One effect of the presence of so much ash into the atmosphere was reducing the amount of available light: no one knows precisely how much sunlight was blocked from the ashes, but estimates range from 25% to 90%. With a 90% reduction of sunlight, plant photosynthesis is reduced at an efficiency of 25% (taking as 100% the amount of light available on a sunny day estiva). La biomassa vegetale probabilmente diminuì dal 25 all'80% (in base alla regione), con periodi di recupero di 30-50 anni.
L'eruzione del Toba causò anche effetti diretti sulla popolazione umana del tempo. Anche se, affrontando questo argomento, si entra in un territorio di accese discussioni accademiche e di differenti risultati ottenuti da calcoli e modelli di simulazione, parte del mondo scientifico sostiene che la popolazione umana subì un drastico calo numerico.
Secondo i sostenitori del "collo di bottiglia genetico" causato dall'eruzione del Toba (come Stanley Ambrose), dopo questo evento catastrofico rimase in vita una popolazione di sapiens tra le 1.000 and 10,000 pairs.
The criticisms of this hypothesis are not few, as well as supporters of the genetic bottleneck that has been actuated by the eruption of Toba. However, things have taken place from the evolutionary point of view, the eruption of Toba is an event that can not be compared to any other in recent volcanic eruption 25 million years.
Today the crater lake Toba is a beautiful, sometimes, to understand what is hidden under his bed through earthquakes and puffs of smoke emitted from one side of the volcanic cones. There is still volcanic activity in the ground: it seems that the Toba eruption of a major genres 300-400000 every year, and the next (statistically speaking) should occur between 200 to 300,000 years.
source: Lightning Fingers
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