Geology And Geophysics

Volcanoes



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Everyone is familiar with the classic science fair experiment of a paper-mache volcanoe.  However, seldom do people truly reflect and attempmt to understand what phenomenon is responsible for the real thing.  How are volcanoes formed?  How and why do they erupt?  Why are they only located in certain parts of the world?


The formation of volcanoes has its origins in the science of plate tectonics.  Simply put, plate tectonics is a scientific principle which states that the most outer layer of the Earth's surface (known as the crust), is not a single, unbroken shell.  Rather it is comprised of a number of plates which interlock much like a jigsaw puzzle.  Of course, over time the edges of these plates have eroded, and due to the large amounts of heat convection which happens underneath the crust, gaps between the plates appear.  In fact, the force with which these plates move is so immense that a plate could find itself pushed underneath another.  Assuming this likely scenario, we see that on the other side of the plate, a rift will open up between two plates.  This rift can emerge into what is known as a volcano, and the molten magma, rock and ash are shot with a violent force into the sky.  


While the classic image of a volcano is more or less a mountain with its top cut off, there are in fact many different forms of volcanoes.  For example, a volcanoe does hot hav to be a mountain at all, it can just be a crack in the earth from which hot magma spews.  These are called fissure vents.  Another type is known as a shield volcano, which is a volcano whose side slope is extremely slight.  This type is formed by the eruption of a great deal of lighter lava, which is able to spread itself out over a greater distance before cooling into rock.  Almost contrary to shield volcanoes are lava domes, which erupt great quantities of thick lava, but only over a short distance.  These are often found in the craters of existing volcanoes.  


However, the most potentially devasting type of volcanoes are appropriately named supervolcanoes.  These are volcanoes who have the destructive capacity to eject over 1000 cubic kilometers worth of rock, magma, ash and debris.  These events are catastrophic and have the potential to influence the way of life of an entire continent, including the ability to start a localized ice age.  


Volcanoes are a fascinating part of the natural world, with an amazing amount of intriguing science around them.   It is integral to the understanding of our world and of how the planet works that we understand the fierce power of these formations.

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