A volcanic eruption might spell doom for most plant and animal species in the immediate vicinity, but the process that leads to eruption isn’t as fast and furious. The reason why volcanoes erupt is mainly due to the high temperature deep down inside the surface of the earth. On an average the temperature inside the surface rises one degree Celsius after every 30 meters. This means that hundreds of meters inside the surface of the earth, the temperature is so high that it melts rocks and creates magma.
Since liquid magma is comparatively less dense that the surrounding solid rock, it rises above the solid rock. This process continues and molten rock, or magma, collect in magma chambers inside the surface of the earth. The explosive process of a volcanic eruption is triggered when the magma chamber is completed filled with magma.
The increase in the quantity of magma inside the magma chamber creates enormous pressure on the surface of the earth, which is hiding all that molten rock. At some point of time, the surface cannot simply handle the rise in the pressure and cracks are formed. Just like rapid decompression, which can bring down even the most sophisticated airplanes in the world, the magma crushes through the surface and explodes into the atmosphere, resulting in a volcanic eruption. The eruption releases hundreds of thousands of tons of magma and other gases into the atmosphere and ceases when the magma chamber is fully or partially emptied, with the process of filling the chamber continuing.
After the volcanic eruption ceases and magma chamber is not pressurizing the surface, the molten rock cools down and solidifies, creating a kind of plug on the magma chamber. However, the quantity of magma inside the chamber continues to rise till the eruption process repeats itself.
