How Fast Does Magma Rise?

The specific volcano they discuss in this article is Plinian, the history of this volcano is brought up and how it is a very violent volcano. These very powerful eruptions tend to occur after a long period of time which then are followed by seismic restiveness. Some of the many volcanoes that show this type of behavior are Mount Vesuvius  in Italy, Mt. Pinatubo in the Philippines and Mt. St. Helens in the USA.Plinian Eruption at Mount St. Helens

Two Professors from Universities decided to do a experiment to find out how fast magma flowed through the chambers to the surface. So they took magma and rocks from this eruption and analyzed it to discover where that rock and magma had come from and to their surprise it was  from the interior of the volcano. This process took four hours to occur so they believed that this type of eruption would give them enough time in order to properly evacuate people that are near the volcano.

“Plinian Volcanoes are characterized by long periods of quiescence, during which they show very little activity. Moreover, the rare eruptions are preceded by quite short bursts of tectonic activity, signaled only by minor earth tremors and increased emission of gas. During the build-up that precedes the eruption itself, magma rises to the surface within a very brief interval, and is expelled from the volcano at high pressure in a huge explosion.”

We have talked a decent amount about volcanoes  and the different types of magma they can produce in this article they discuess the Velocity of the magma raising and how what it is made up of will affect that. The professors were able to take samples of the hardened magma and do an analysis of it. ‘While being heated to a temperature of 825 degrees centigrade at high pressure. After a certain time under these conditions, characteristic crystalline margins begin to develop around the feldspar crystals in the pumice.’ This then brought them to the conclusion that the magma was rising to quick and did not allow it enough time to form crystalline. We talked about this for a day in class and i found it interesting and very logical to understand its just cool to read about something such as this and be able to understand it and why it occurs.

Rising magma beneath Chaiten volcano

” The researchers were surprised by the results of their analysis. Their calculations suggested that the rock fragments they had collected had ascended from the earth’s interior to the crater floor in less than four hours. To accomplish this, the material must have risen at a rate of about one meter per second.” This was a very big shock to them because it meant that Plinian can develop with great speed which would not allow them to react in enough time in order to perform a successful evacuation. Which makes this volcano high risk. They then go on to discuss how certain types of volcanoes have certain tell tail signs of when it is about to erupt and possibly what to expect with that eruption.



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