By ItsNotMagicItsScience

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Lava may look pretty as it weaves its molten way, but underneath they are pure power. Volcanoes are one of the most awesome and destructive spectacles on our planet.

We all know that gas, oil and other minerals and natural resources are found deep under the surface of the planet. But below these solid layers of the earth’s crust lie lakes of hot bubbling liquid that occasionally find their way to the surface with spectacular results.

You may have seen the pictures of lava flowing out of the Kilauea volcano on the island of Hawaii, creating banks of steam as it explodes and solidifies upon contact with the ocean. What you might not know is that it has extended the area of the island by over 200 hectares since it started erupting in the 1980s.

More recently, eruptions of volcanoes like Mount Merapi in Indonesia and Eyjafjallajökull in Iceland (try pronouncing that!) have caused their own chaos, causing thousands of residents to be evacuated to safety and creating ash clouds that have disrupted air-travel across the world.

So while they might sound scary, volcanoes are an everyday part of our world, and they’re a lot more common than you might think. Volcanic eruptions and the rock and lava they spew out have helped to form the surfaces of entire island chains like Hawaii. Today it’s estimated that there are around 600 volcanoes that have erupted that mankind has recorded. However, throughout the entire history of our planet there may well have been millions of them, helping to shape the ground some of us live on today.

Like Kilauea, there are around 20 volcanoes erupting every day, with around 50 or more that are classified by volcanologists, the scientists who study volcanoes, as being active. But before you hide under the table, there are lots of different types of volcanoes and not all of them are catastrophically destructive.

There are lava domes, fissure vents, stratovolcanoes, cinder cones, cryptodomes, even submarine volcanoes on the seabed and more. Some volcanic fields can contain dozens of combinations of these bubbling and towering creations. While they are all slightly different in the way they erupt, you can think of them as holes – a bit like a cut or a graze on your skin – but on the surface of the planet.

These ruptures allow the boiling hot magma and superheated gases in the planet’s mantle to be forced upwards when heat and pressure or the movement of the Earth’s tectonic plates create gaps or tunnels that allow them to escape. Like earthquakes, they are our planet’s way of releasing energy and blowing off steam.

There is a kind of volcano that stands out from all the rest. Supervolcanoes are the most dangerous kind of volcano, with the ability to have an effect on life on entire continents. When Mount Tambora in Indonesia erupted in 1815, in what was the largest eruption on record, the noise of the explosion was heard 2,000km away on Sumatra island and ash fell on Borneo as well as other islands throughout the South China Sea.

Its effects were also felt across the globe. Referred to as ‘The Year Without Summer’, sulphur from the Tambora eruption was dispersed high into the stratosphere – the layer of the atmosphere that lies between 10km and 50km above the surface – this caused a haze, also referred to as a dry fog, to envelop much of Northern Europe and North America. Here, it caused temperatures to drop and triggered a range of extreme weather events that led to crops failing, mass hunger and even famine throughout 1816.

However, Mount Tambora isn’t even a supervolcano. The last known supervolcanic eruption happened over 25,000 years ago at Lake Taupo in New Zealand. But one of the most devastating of all time happened when the Toba volcano in Indonesia erupted nearly 75,000 years ago.

That explosion created Lake Toba, a caldera – a cauldron shaped void – that filled with water and measures more than 100km in length today. It blasted thousands of cubic metres of rock, gases and ash into the atmosphere, where they fell to ground throughout South East Asia. In some parts of Malaysia, geologists have discovered layers of Toba ash almost nine metres deep, and, incredibly, layers as deep as six metres have been found as far away as India.

Geologists have even found a thin layer of sulphuric ash, a few centimetres deep in the fossil record in the United States that corresponds to the Toba incident. Of course, the areas around Toba were flattened and destroyed, but the effects were felt across the entire planet. Ash, dispersed by the wind high in the stratosphere, reflected the sun’s rays, preventing them from reaching the ground except in a hazy trickle, which caused global temperatures to drop by as much as 5°C.

Those thickly layered carpets of ash would have stopped plants, trees and crops from growing. At the same time, sulphur and other compounds from the eruption mixed with rain, poisoning the earth and waters and killing plant life in parts of the world that the ash didn’t reach. All told, it created a volcanic winter that raged across the planet for as long as six years which some scientists estimate may have killed around 60% of the world’s human population of the time, reducing it to a core of 40,000 people or less. This is about the size of a medium sized town!

Of course, with time, the pollution reduced, temperatures increased and as volcanic soils became fertile, plants, animals and people thrived again. Those 40,000 people are now a staggering six billion. But are there any other supervolcanoes we need to be wary of? Almost the whole of Yellowstone Park in the United States is a massive caldera. It last erupted over 600,000 years ago. Fortunately, although the floor of the caldera is constantly moving upwards at a rate of few centimetres a year, experts are pretty sure that there won’t be any catastrophic eruption in the near future, so for now, people are free to enjoy the beauty, the geysers and heated springs that are a feature of the Yellowstone National Park, which sits safely on top of this huge pool of molten rock.