Natural disaster effects: Volcanoes

When volcanoes erupt, they can spew rock, ash, and gases for many kilometres. They can put people, property, and entire ecosystems in danger. A volcanic eruption is a natural disaster. Active volcanoes can erupt at any time, which is a bit scary to think about! But luckily, there are almost always warning signs in the days, weeks, months, or years before.

What are these signs? Before a volcanic eruption, the ground may start swelling, sinking, or cracking, due to the movement of gas and fluids underground. That’s because beneath the Earth's surface, there is extremely hot rock that behaves like a liquid. It is called magma. When pressure builds in the crust, magma starts to move upwards towards the surface through vents and cracks.

As magma moves upwards, the surface of a volcano may get hotter. It may start spewing more gas than before. There may even be hundreds of small earthquakes. Monitoring these signs can help scientists predict and prepare for potential eruptions. When magma reaches the surface, it's called lava.

Sometimes, lava flows gently from a volcano in non-explosive eruptions. But, if a lot of gas is trapped within magma, pressure will build and build until eventually lava erupts explosively out of the volcano, sending hot ash and rock flying. That’s what happened when Parícutin formed in Mexico. It appeared suddenly out of a cornfield during a single explosive eruption! Ash and lava were blown into the air through a single opening called a vent.

It hardened and fell into a simple cone shape, creating a cinder cone volcano. Other volcanoes take shape over many eruptions. Mount Vesuvius in Italy, for example, is known for its history of explosive eruptions. After each eruption, a new layer of solidified lava, volcanic ash, and other volcanic materials forms over the previously-formed layers. So we can say that Mount Vesuvius is a volcano built up of many layers.

It is a composite volcano. What about volcanoes that experience mostly non-explosive eruptions? What do they look like? Mauna Loa in Hawaii is an example of a shield volcano. When this type of volcano erupts, it produces thin, runny lava that spreads far and wide.

This creates a large, dome shape that looks a bit like a warrior’s shield. Because most shield volcano eruptions are non-explosive, they are sometimes described as 'quiet' volcanoes. Even so, their lava can flow quickly and cause a lot of damage. Volcanic eruptions, both explosive and non-explosive, can be disastrous. Flowing lava can burn everything in its path.

Falling ash can disrupt transportation, damage crops, and pose health risks to people and animals. It can be very expensive to rebuild and replace collapsed or destroyed buildings. Sometimes, entire communities must be relocated. However, volcanic eruptions can bring some benefits. Around the world, people live close to volcanoes because the soil is very good for growing crops.

Volcanic ash is rich in nitrogen, which makes the soil ideal for growing a variety of plants, fruits, and vegetables. And the heat from a volcano can be useful too. Underground water and steam heated by magma can be used to generate electricity. This is called geothermal energy. Volcanoes cause change on Earth.

Recognizing the potential dangers and benefits of volcanoes can help us better live alongside them.