Mount Toba – Super Volcano
The Jakarta Times reported, yesterday that geologists fear that Mount Toba, on Sumatra may erupt again as a super volcano. Toba has already accounted for the largest known earthquake in the last 2 million years when it spewed out more than 2,500 cubic kilometers…that’s kilometers, not meters….of magma and which ultimately resulted in the formation of the world’s largest quaternary caldera’s (35 x 100 km) that is now Lake Toba.
The scientists, who include Craig A. Chesner of Eastern Illinois University have identified a huge magma chamber at a depth between 20-100 kilometers. The concern is that one of the frequent earthquakes in the region could set off an eruption, which would have potentially devestating consequences.
Indonesia consists of more than 13,000 islands, spread over an area the size of the United States. It has the greatest number and density of active volcanoes with 129 being actively monitored by scientists. Most volcanoes in Indonesia stretch from NW Sumatra (including Mount Toba), to the Banda Sea and are largely the result of the subduction of the Indian Ocean crust beneath the Asian tectonic plate. As if this were not enough, there are other subductions that make the picture more complex and….more dangerous.
Unsurprisingly, it also has the largest number of historically active volcanoes (76), and the second largest number of dated eruptions (1,171) exceeded marginally by Japan (1,274). Indonesian eruptions have also caused the highest number of fatalities, damage to arable land, mudflows, tsunamis, domes, and pyroclastic flows. 80% of such dated eruptions have erupted since 1900 although such analysis only stretches back to the 15th century!
Two of the most cataclysmic volcanic eruptions in recent history include the devestating eruption of Tambora in 1815 which altered the world’s weather to such an extent that, in Europe, 1816 became known as ‘the year without summer’. More famous was the disastrous eruption of Krakatau in 1883, not so much due to the magnitude of the eruption as to the magnitude of the tsunamis. Tsunamis accounted for 30-40,000 lives and secured Krakatau’s place in the collective memory of the world.
All of these volcanic eruptions create igneous rocks of one kind or another. Under a microscope, they can help tell the story of what happened and when while also presenting a glorious array of colors and crystals. Polarizing microscopes are best used for examining such rock specimens but surface textures an colors can be viewed with our new Explorer Series Rock Hound packages.