#shiveluch

Lava domes form when viscous magma is pushed up but can’t get out of the way. The outer layers exposed to the air cool and solidify while the inside is still moving. This process can build up pressure that triggers explosive eruptions if gas can’t easily escape cooling magma, and it can also trigger large collapses and associated explosions if the lava dome becomes oversteepened. A collapsing lava dome is a nightmare for anyone nearby; blocks of solidified lava are mixed with still molten lava and race down to lower ground, forming a type of pyroclastic flow called a Block and Ash flow. Shiveluch has built up several lava domes over the past century, with occasional collapses as you see in these 2 photos. Most of the volcanoes of Kamchatka occur because the Pacific plate is subducting beneath the smaller Okhotsk plate, which is mostly hooked to the continent of Asia. At the northern tip of the subduction zone, the Ohkotsk plate meets the North American plate and the Aleutian Island trench, creating a complicated triple junction where the Pacific Plate is sinking beneath 2 different other plates. In the process, the subducted plate actually seems to be ripping into two pieces, in the process allowing hot mantle rocks to leak upwards through the tear. That extra heat feeds some of the most active volcanoes at the northern end of the Kamchatka arc, including Shiveluch. -JBB Image source: https://www.researchgate.net/publication/261706569_Arenal_Costa_Rica_Activity_and_seismicity_decrease_new_analysis_of_acid-rain/figures?lo=1 References: https://volcanohotspot.wordpress.com/2015/03/18/tectonics-of-the-kamchatka-peninsula/ http://www.eri.u-tokyo.ac.jp/people/ichihara/vp2009plan/DavailleLees2004.pdf