Worlds in Eruption

Worlds in Eruption - Volcanoes

Volcanism, in its various guises, is without doubt one of Nature’s most spectacular and fearsome displays of power. Volcanic eruptions – like those of Krakatoa, Mount St Helens or Montserrat – destroy huge areas of land and can kill thousands of people.

Volcanic activity is also, arguably, the most important of all geological processes. It makes its presence felt from hundreds of kilometres below the Earth’s crust up to the cruising altitudes of commercial airliners. It resurfaces continents, alters climate patterns and – in the long term - may cause mass extinctions of life. For geologists, volcanoes also serve as windows through which they can peer into the heart of the Earth - windows that give invaluable insights into the processes churning away below our feet.

But Earth is far from being the only planet where volcanism has played a salient role.

For over thirty-five years a flotilla of interplanetary spacecraft has set sail for new worlds beyond our own. These intricate robots, bristling with sophisticated instruments, act as our remote senses: seeing, listening, and in some cases touching the surfaces and smelling atmospheres of other distant bodies. They have presented us with conclusive evidence that the effects of volcanism are ubiquitous throughout the Solar System.

Many of these volcanic constructs dwarf anything we find on Earth. And, by studying extraterrestrial volcanoes and the material they throw out, planetary scientists are slowly unravelling the complex geological processes that have sculpted other worlds.

The volcanic power plant

What causes volcanism? There are two basic ingredients needed to make a volcano: heat, and something to melt. The latter is straightforward. Be it rock or ice or a mixture of both, if you add enough heat it will eventually melt. This gives you the molten stuff – magma. When magma escapes to the surface it erupts to form lava flows, which - along with ash and larger boulders - constructs a volcanic cone.

NASA Volcanic plumes spew forth from the surface of Io.

But where does the heat originate? The first source is primordial heat, the energy left over from a planet’s formation. It was generated when immeasurable numbers of planetesimals (comets and asteroids of all shapes and sizes) collided at hyper-velocities to build up the planet. The impacts liberated large amounts of energy, mainly in the form of heat.