Tuesday, February 1, 2011
This semester in my classes we are learning about volcanoes, and everything that goes with them. So I thought I would share with you some of what I learned first off geologist have a index rating for volcanoes that is similar to the rector scale meaning a change from a 1 to a 2 is 10 times more powerful. This scale is called Volcanic Explosivity Index (VEI) (check the link for more info)and ranges form 0 to 9 in intensity rating. Each volcano has a different rating based on the plume height, frequency of eruption, its occurrence, and the total amount of ejected material. With a little back ground I wanted to share some new knowledge about a type of volcano that I did not know much about they are called a “Maar” volcanoes and are very deadly. They form like any other volcano by magma rising to the surface however in this case the magma comes into contact with an underground aquifer. Water is instantly flashed to steam and as a super heated gas it need to expand rapidly but being trapped under ground applies pressure which is quickly over powered in a atomic like explosion earning a VEI of 5-6. Some of these eruptions produce super heated plumes that can rise 55 kilometers in the atmosphere in case you are wondering NASA describes space as starting at 100 kilometers from the surface of the earth just to give you an idea of the height these plumes can reach. They produce pyroclastic density currents(PDC) which are super heated ash flows that can travel up to 100 miles an hour, destroy anything in there path. These PDC are what is responsible for the destruction of the city of Pompeii and all the people that lived there (note Mt. Vesuvius is not a maar but is a Strato-volcano like Mt St. Helens). It is common to find maar’s as a shallow lake sometimes as deep as 10 to 200 meters and as wide as 60 to 8000 meters. I will describe more volcanoes and what I have learned in upcoming posts but until then get to know what your walking around on.