What Makes Volcanos Erupt?

While you probably studied volcanoes a bit when you were in high school, their actual mechanics may still be a bit fuzzy to you. There might have been a few bits and pieces about plate tectonics and pressure, but how these massive eruptions actually occur is usually outside the range of the average person’s knowledge. Given the recent eruptions in Hawaii, though, it’s a good time to learn a bit more about this natural phenomenon. Not only are volcanic eruptions a normal part of the process of a changing globe, but learning more about their mechanics can help you to better appreciate these spectacular – and dangerous – events.


Plate Tectonics

As you might remember, the surface of the Earth is composed of a series of tectonic plates that move over the liquid mantle. As these plates move and shift, a number of possible situations can occur. What’s important to remember here, though, is that the solid matter of the Earth is often subducted under another plate at the boundary points. When this subduction occurs, the solid mass is turned into a melting-hot form of liquid rock known as a magma. The creation of magma does not necessarily lead to the creation of a volcano, but it is an important part of the process.


Density at Play

When the solid rock of the crust melts, it becomes less dense than it was in its solid form. While the actual volume of the substance remains the same, both the newly-formed liquid rock and its accompanied gases are far more buoyant than they were before. This means that the material is lighter compared to its surrounding solid rock, and thus it will begin to lift. The rock and gases exert a tremendous amount of pressure on the surrounding area, causing it to rise – this gives birth not only to the traditional raised mass of a volcano, but it is also responsible for the creation of new islands in the world’s oceans.


Under Pressure

As the magma continues to rise, less pressure is exerted on it. While you might think that this would stop any kind of violent activity, the truth is that it’s at least partially responsible for some of the more spectacular explosions. As pressure decreases, water bubbles begin to nucleate away from the greater mass of the magma. As they rise, they continue to bring the magma rushing faster and faster towards the surface of the Earth. Once there is a sufficient amount of pressure and built-up magma, there will be an explosion – in some cases sending magma hundreds of feet into the air.


A Continuing Process

The actual violent eruption of a volcano is only one part of the overall process. Once the initial burst of lava escapes the top of the mountain, more super-heated rock and gas will continue to escape from the new fissure in the Earth. It’s a bit like shaking up a can of soda and then opening the bottle – the initial explosion is intense, but a fair bit of the soda will continue to leak out after. Lava can continue to move out of the volcano for some time even after the most spectacular parts of the explosion occur.

The mechanics behind volcanoes are, of course, a bit more complicated than those listed above. This basic explanation will, hopefully, help to put what has happened in Hawaii and that will continue to happen around the world in context. Volcanoes are just one part of an ever-changing world, and one of the forces that help to shape the face of the planet.

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