Monitoring Volcanoes

How do we monitor volcanoes?

Volcanoes give us clues about whether they're going to erupt soon or not. We can't always be sure, but monitoring volcanoes helps us to have some idea about future eruptions. We can do this by monitoring the shape of the volcano, the amount of heat it gives off, the shaking of the land, and the gases present in the air.

Ground deformation monitoring volcanoes

When we talk about ground deformation in the monitoring of volcanoes, we are talking about changes to the surface of a volcano. Imagine a volcanic eruption for a second. Think about how magma rises up through the volcano and then eventually makes its way onto the Earth's surface as lava. What do you think happens to the ground when this happens? It is common for a volcano to swell up when an eruption is near. This happens as the magma rises up through the volcano.

The volcano's surface doesn't just change by swelling. Other potential pre-eruption changes can include the cracking of the ground because of the pressure of the magma moving inside the volcano.

Even though a lot of lava can spew out of a volcano during an eruption, the changes in the ground (ground deformation) are actually quite small (usually.) Because of this, scientists need to use sensitive equipment to pick up the changes. The most common piece of equipment that does this is called a tiltmeter. You might have guessed from 'tilt' being in the name, but this type of device measures how tilted the landscape is. This way, if there is any swelling we need to know about, the tiltmeter should pick up on it. Scientists sometimes also use data from satellites to look at how the shape of a volcano is changing.

Fig. 2 - Using GPS on La Réunion island to look at the ground deformation of the volcano.

Seismic monitoring volcanoes

Seismic - wait - isn't that to do with earthquakes? It is, indeed. If you've read our explanation of Earthquakes, you'll know that an earthquake is the shaking of the Earth's surface caused by moving tectonic plates. The word 'seismic' is used to relate to all things earthquakes. Any guesses on what seismic monitoring is, then?

Seismic monitoring of volcanoes is used to measure earthquakes happening near a volcano. These earthquakes happen more often and more intensely near the time of a volcanic eruption because the movement of magma causes the ground to shake (earthquake). So, how do we measure these earthquakes? Seismometers are special devices that pick up the seismic waves caused by earthquakes. If the seismometer picks up on lots of earthquakes, it might be because a volcanic eruption is around the corner.

Gas monitoring volcanoes

Volcanoes don't just release lava - they also release gas. The main gases that are released near a volcanic eruption are carbon dioxide (CO₂) and sulphur dioxide (SO₂). SO₂ is toxic and causes humans to develop respiratory (breathing) problems if they inhale too much of it.

Two main ways of gas monitoring are:

1. Gas-trapping bottles - these bottles will trap any gas so it can be analysed.
2. Robots called 'Spiders' - this is a special device that measures gases coming out of a volcano.

An increase in any of the gases can, and probably will mean an impending eruption.

Fig. 3 - Volcanic gas of Mount Aso, Japan

Thermal monitoring volcanoes

Thermal vests, thermal leggings, thermal flasks - all of these things are to do with heat.

Thermal monitoring of volcanoes, then, focuses on the heat coming off a volcano. It probably comes as no surprise, as magma and lava are very hot. Lava can be over 1,170°C - definitely not something you want to touch or get too near to! Do you think a volcano releases as much heat during an eruption as it does when magma is not rising up through the volcano? No - volcanoes release much more heat as an eruption gets nearer. This means that if we monitor a volcano by measuring its temperature, we can guess when magma is rising up through a volcano and therefore that an eruption might happen soon.

Water temperature measurement

Alongside doing thermal measurements on the volcano's surface, as mentioned above, scientists also measure the temperature of the water in streams and rivers. An increase in the water temperature can be an indication of an impending eruption.

Why do we monitor volcanoes?

Why bother? Why spend lots of time, effort and money on using what can be very expensive equipment to monitor volcanoes? Volcanic eruptions can have a large range of impacts on people and the environment. People dying, villages being destroyed, habitats being wiped out, and the economy suffering is all impacts that people have suffered because of volcanic eruptions near where they are living. We monitor volcanoes to try and stop these things from happening or to reduce the damage that these impacts have. Predicting volcanic eruptions can help us to get people into 'safe zones', far away from where the volcano will erupt; it can also help us to get emergency supplies ready and support people in what can be a difficult and dangerous time. Monitoring volcanoes doesn't just teach us more about how volcanoes work - it can also save lives.

Monitoring volcanoes summary

Let's look at a summary of the information given throughout this explanation:

• Volcanoes can be monitored in different ways:
  • Seismometers measure the earthquake that occurs near an eruption.
  • Thermal measuring of the volcano's surface to indicate any temperature changes that occur close to an eruption.
  • Measurements of the temperature of water sources close to the volcano. Any increase can indicate an impending eruption.
  • Tiltmeters and GPS satellites monitor any landscape changes (ground deformation), such as the swelling of a volcano near an eruption.
  • Gas monitoring by using gas-trapping bottles, such as so-called Spider robots. Gases such as carbon dioxide (CO₂) and sulphur dioxide (SO₂) are being released by a volcano, but the gases will increase near an eruption.
  • Looking at past eruptions can help discern a pattern which might be helpful in monitoring and predicting future eruptions.
• Monitoring volcanic eruptions are of vital importance. Eruptions can damage villages and land, destroy (wildlife) habitats, and it can cause people to be displaced, injured or die. This will also have significant economic impacts.