Living with volcanoes

Discovering Geology – volcanoes

Volcanic eruptions are often dramatic events that attract attention, sometimes on a global stage. Out of curiosity and awe, we are often drawn to volcanic landscapes to view the awesome power of nature first hand.

But, what about the people that live alongside an active volcano every day? On first thought, it may seem unwise to choose to live with such hazardous neighbours, but all of us live with risk every day, we just weigh the risks up against the benefits. Here are some of the main reasons why people live alongside volcanoes:

  1. Volcanic environments can be good locations for farming. Erupted volcanic material, particularly some forms of ash, can create fertile soils that are ideal for growing crops. In response to frequent eruptions, some farmers have adapted their crops, and farming styles, to suit different types of ash.
  2. Volcanic environments often evoke a strong sense of place. Whether that be driven by aesthetics, community, history, culture or religion, ‘volcanic communities’ often have a very strong bond with ‘their’ volcano and assign strong symbolic meanings to their environment.
  3. More than that, volcanic environments are simply just home for many people. That’s where their family, friends and jobs are.
  4. Volcanoes evoke wonder and attract millions of tourists around the world. This supports local economies and provides jobs.
  5. Volcanic environments can produce rich mineral deposits and be tapped to provide geothermal energy for nearby communities.
  6. Practically, some people just cannot afford to move elsewhere.
  7. And sometimes, people are forced by others to live in these environments.

Eruptive products, and the forces that produce them, shape the landscape, sometimes removing land and sometimes adding to it. For example in 1973, the volcano of Eldfell on the island of Heimaey in Iceland erupted. Heimaey has Iceland’s only harbour in the south of the country and for a few months it appeared that this would be destroyed. However, the lava did stop flowing having increased the land area by over 2 km², and enhanced the shape of the harbour, making it more of a safe haven for the fishing fleet than it was originally!

Crops growing in the fertile soils of the Popocatepetl volcano, south of Atlixco, Mexico.
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Crops growing in the fertile soils of the Popocatepetl volcano, south of Atlixco, Mexico. Source: © Alexander Schimmeck, Unsplash

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Volcanic deposits are enriched in elements such as magnesium and potassium. When volcanic rock and ash weathers, these elements are released producing extremely fertile soils. Thin layers of ash can act as natural fertilisers producing increased harvests in years following an eruption. Volcanic deposits (particularly ash) are also quite porous, retaining moisture longer than many non-volcanic soils. As a consequence, land close to a volcano is often good for agriculture.

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Close to home: living and farming with volcanic ash. Eruptions of Volcan Tungurahua in Ecuador, from 1999 until 2016, produced ash fall that affected people living on the slopes of the volcano. Source: Strengthening Resilience in Volcanic Areas project.

Volcanic areas can also become rich resources of ore deposits when rocks are ‘cooked’ in extremely hot water — a process called hydrothermal alteration. The country of Cyprus, which roughly translated means copper, owes its name to the mining of copper deposits. This copper occurs in parts of the Earth’s crust that has been pushed upwards; long ago, seawater circulated through the volcanic oceanic crust and was heated up to 350°C. This heated water became acidic and corroded the rock through which it was flowing, becoming enriched in elements such as copper. On cooling minerals such as copper sulphides were deposited.

Roman coins made from copper
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The Roman supply of copper came almost entirely from Cyprus; it was known as aes Cyprium, ‘metal of Cyprus’. Source: Thanasis Papazacharias /Pixabay

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Many countries with active volcanoes are able to use the heat generated by volcanic activity as geothermal energy (e.g. Iceland and New Zealand). Water in the upper crust of the Earth is heated above a magma chamber or rocks that are still very hot; this is often apparent on the surface due to the presence of hot springs or geysers. To use this water as geothermal energy, the water needs to be pressurised. Pressure builds up when the boiling water is trapped beneath a dense impermeable rock layer, such as a clay, preventing it from expanding. By drilling a deep hole through this layer, the steam rises to the surface and expands, either driving turbines or being directed through heat exchangers.

Nesjavellir Geothermal Power Station
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In Iceland 25% of the country’s total electricity production is from geothermal energy and over 66% of their primary energy use, including the heating of nine out of ten homes. Source: WikiImages / Pixabay

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References

British Geological Survey. 2012. Geohazard note: Volcanic hazards. British Geological Survey.

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Plymouth, Montserrat. Mud flow deposits at clocktower.

Volcanoes

There are more than 1500 active volcanoes on Earth. Around 50-70 volcanoes erupt every year. There are 82 volcanoes in Europe, 32 of these are in Iceland, one of the UK’s closest ‘volcanic neighbours’.

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Effusive andesitic lava dome, Montserrat

Eruption styles

Volcanic eruptions can be explosive, sending ash, gas and magma high up into the atmosphere, or the magma can form lava flows, which we call effusive eruptions. Whether an eruption is explosive or effusive largely depends upon the amount of gas in the magma.

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Mt Fuji, Japan from space

Types of volcano

When magma erupts at the surface, as lava, it can form different types of volcanoes depending on the viscosity, or stickiness, of the magma, the amount of gas in the magma, and the way in which the magma reached the surface.

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Anak Krakatau volcano

Volcanic hazards

A volcanic hazard refers to any potentially dangerous volcanic process that puts human life, livelihoods and/or infrastructure at risk of harm.

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Footnotes

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