alex here brian al jazeera shan cronan and his vulcan ologist and oakland university who studied this volcano. he explains what triggered such a massive explosion. this was the culmination of magma building up inside the spokane for quite some time. so it's full of magnetic gas, so it's full of trapped gas with inside the magma. and as the magnet pressure rises within the volcano, and as the gas pressure rises, eventually the volcano can no longer hold up. and so there was a sudden release of back gas to produce the erupt from all of these very large explosions are very impulsive explosions. produce an atmospheric shock quite so you imagine that's the top of the volcano around 150 to 250 meters below sea level and is that material sort of rises out of a rapidly rises at the top of the volcano, you bulge of expanding magnor and gas that's just bursting out and it's bursting out through the water and in through the air, what happens is the, it gets compressed into the shock waves and they were traveling around the world. the remarkable thing about this erection was your head, the rapid