Science Behind the Biggest Global Hazard in Feb 2018, the Sinabung Volcano Eruption! GEONEWS EP2

One of the most active Asian volcanoes, Mount Sinabung, exploded on Feb 19, and created a volcanic ash plume 5 kilometers into the air. Why was the explosion so violent? It is because Mont Sinabung is located at the Indo-Australian and Eurasian convergent plate margin. The thinner and denser oceanic part of indo-Australian plate goes underneath the thicker and less dense Eurasian continental plate. The process is known as "subduction" in Geology. The crustal portion of the subducting Indo-Australian slab contains a significant amount of seawater, as well as water contained in hydrated minerals within the seafloor basalt. As the subducting slab descends to greater and greater depths, it progressively encounters greater temperatures and greater pressures, which cause the slab to release water into the mantle wedge underneath the Eurasian plate. Water has the effect of lowering the melting temperature of the mantle, thus causing it to melt. Because of the high pressure in the mantle, the magma dissolves plenty of volatiles (mostly water vapor and carbon dioxide). As the magma beneath Mount Sinabung rose up towards the surface, the pressure decreases, and the volatiles came out of solution and formed bubbles in the magma, just like what happens when you open a shaken soda can. Moreover, because magmas produced by this mechanism are often more silica-rich than magmas of other tectonic settings, the bubbles in the magma cannot easily escape. They must explode their way out of the magma creating huge ash clouds.

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