Pumice is way too fun.In 1912, a volcano named Mount Katmai unleashed the largest eruption of the 20

Pumice is way too fun.In 1912, a volcano named Mount Katmai unleashed the largest eruption of the 20th century. Katmai sits near the base of the Alaskan Peninsula, above the subduction zone where the Pacific plate subducts beneath the Aleutian Islands. The actual vent that erupted was a dome near the edge of the larger volcano named Novarupta.The volume of material thrown out by that eruption was 3x that erupted by Mount Pinatubo in 1991 and 10x that erupted by Mt. St. Helens in 1981. Here you see a portion of that material represented as pumice and captured by National Geographic Magazine over 90 years ago. Pumice is a rock full of holes and gas pockets. Explosive eruptions like that at Novarupta occur when gases dissolved in magmas force their way upwards towards the low pressures in the atmosphere; moving so fast as that the magma shatters and breaks into large chunks even though it is still hot.The gases dissolved in magmas migrate to spots called vesicles that are basically gas-filled holes in the magma. Magmas can build up so many vesicles in them that, after eruption, the majority of the volume of pumice can be air, making the rocks ridiculously light and, well, incapable of crushing people very easily.-JBBImage credit: NatGeo Foundhttp://natgeofound.tumblr.com/post/71973021405/a-man-balances-a-piece-of-pumice-rock-on-his-legsRead more:http://www.volcanodiscovery.com/katmai.htmlhttp://www.wired.com/wiredscience/2012/06/the-biggest-bang-of-the-20th-century-the-1912-eruption-of-novarupta-in-alaska/ -- source link

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