How Things Work: Volcanoes

Credit: Maria Raffaele/Art Editor Credit: Maria Raffaele/Art Editor

A recent volcanic eruption in Iceland created mayhem, causing evacuations and widespread flooding in the country. Other parts of western Europe were affected as well, as volcanic ash grounded planes. While volcanic eruptions and ash become the center of the spotlight for breaking news, it is important to understand the nature behind the fearsome and destructive power of volcanoes.

Most humans will only see the surface of the earth, but thousands of kilometers of molten rock exist beneath our feet, under the solid ground on which we live. This molten rock is called magma, and it sometimes makes its way to the surface of the earth through volcanoes. The exit of magma can sometimes be forceful, resulting in a volcanic eruption.

Usually, magma exists as solid rock, according to the website This is because of the enormous pressure that exists under the earth’s surface, which prevents magma from becoming a fluid. However, there are occasions when magma can rise closer to the surface when pressure is released. This is explained by plate tectonics, a theory that the earth’s surface is composed of interlocking plates that move in the inner regions of the earth. Sometimes, the boundaries between these plates separate, allowing magma to rise between them. Other times, the plates will crash into each other such that the edges move downwards, which also forces magma to flow upwards between the plates.

The reason magma is forced upwards is a result of differences in density between the layers of the earth. When magma becomes more fluid, its density decreases relative to the rock by which it is surrounded. This is the same reason why helium balloons rise in air — the density of helium is less than that of air. Most magma eventually becomes trapped in magma chambers just below the earth’s surface, but some will find a way to the top.

Magma erupts because of the gases that become dissolved in it. Again, eruption has to do with pressure; once the confining pressure of surrounding rock becomes less than the escaping pressure of gas, the gas will erupt out of the earth’s surface and carry magma with it. The power of volcanic eruptions is dictated by the amount of gas in the magma, as well as how resistant the magma is to its gases escaping. If the magma has a higher resistance, more gas pressure can build up before it erupts, causing a stronger eruption.

A volcano describes any sort of opening on the earth’s surface through which magma or gases can erupt. While frequently associated with explosive eruptions, another common type of eruption forms effusive lava, which is slow moving.

The reason why Iceland’s volcano is causing so much trouble is because of the force of the volcanic eruption, which sent columns of ash into the air. Wind has scattered ash into the atmosphere of many countries in Western Europe, preventing planes from flying. In addition, according to, magma from the eruption also melted 200-meter thick glaciers, causing extensive flooding that tore down bridges, roads, and homes. Ash in the atmosphere reduced visibility to mere yards, and many people near the eruption had to evacuate their homes and find refuge in Red Cross shelters.

Although volcanoes are associated with fire and destruction, they play an important role in shaping the earth’s surface. They are involved with the creation of islands, and volcanic rocks add nutrients to soil.