Question: What would happen if you were near or on a volcano and it erupted?

Natasha Dowey answered on 4 Mar 2019: last edited 4 Mar 2019 11:47 am

This is something I’ve thought about a lot. When I was working on Santorini in Greece and Tenerife in Spain, I was working right on top of dormant volcanoes. That means a volcano that isn’t erupting right now, but is just sleeping, and will very likely erupt in the future.

Normally, before a volcano erupts, there would be some warning signs- but not always. As magma moves beneath the ground, it causes the rocks to strain and adjust, and may cause earthquakes to occur. A lot of volcanoes around the world have seismometers on them- these are machines that tell us about the little earthquakes inside the volcano. If earthquake activity was unusual or increased, it may indicate that an eruption is going to happen. Volcanoes also release gases, and if a volcano were about to erupt these gases may change or become more intense (basically, the volcano could get really smelly!). So- you would hope that there would be warning signs, and that the local government would release warnings about what is likely to happen, and whether you should be evacuated.

So, let’s assume that we’ve had some warning signs, and we’ve been evacuated to a safe distance with the other local people. What would happen next would depend on the type of volcano. Some types of volcano are highly explosive (the type that I studied). These eruptions would likely occur with quite a dramatic bang, and would send clouds of gas, ash and rock high up into the sky. Ash and pumice, a type of volcanic rock, may rain down from the sky, covering peoples homes. This can be dangerous for people, breathing in the ash, or because their rooves are in danger of collapsing under the weight of the rock. The most dangerous type of hazard in this kind of eruption is known as a “pyroclastic density current”, which is a hot cloud of ash, gas and rock that emerges from the volcano and travels at very high speed through valleys. Recently this happened at the Volcan del Fuego Guatamela eruption last year, in which many people sadly lost their lives.

Not all eruptions are explosive- many are “effusive” which means they are more likely to erupt rivers of lava than clouds of ash. In this type of eruption, you may expect fountains of lava to be erupted from either a central vent, or from lines across the landscape called “fissures”. This kind of eruption occurs on Hawaii- last year they had a really long period of lava eruptions. Lava is a different kind of hazard- it can release a huge volume of dangerous gas into the environment (Hawaii is not a pleasant place to live for asthma sufferers), and can cover large areas, destroying crops, homes, and roads.

Either way, the safest place to be is as far away as possible. Although volcanologists study volcanoes, they tend to study them when they are quiet. Some are trained to study them during eruptions, but must take very great care to do so.