Geohazards explains why and how to monitor volcanoes

Volcano seismic station equipped with monitoring system (Seismic and visual-seen in next photo) at Mt Yasur on Tanna.

The sole body mandated to monitor volcanoes in Vanuatu is the Geohazards Division under the Vanuatu Meteorology and Geo-Hazards Department (VMGD) in Port Vila. Geohazards explains why and how to monitor volcanoes.

Why do we monitor volcanoes in Vanuatu?

In Vanuatu, we have many active volcanoes and many people live near the volcanoes. Any future eruptive activity should be watched out for so people living nearby are kept safe.

Monitoring volcanoes will allow for an estimate of the sizes and styles of any eruptions, and their consequent threats to lives and property.

This information can keep people safe.

How to monitor active volcanoes:

Volcanic monitoring assumes that movement of molten rock (magma) beneath a volcano will occur before any eruption can start.

The two best techniques used around the world to monitor volcanoes are visual and seismic. Therefore, the easiest way of monitoring a volcano is just by looking at it!

However, it is not possible for a scientist to visit a volcano every day so we now use remotely operated cameras for those observations.

Our volcano web cameras are specifically designed for remote operation. The controlling computer asks them to take a photo at regular intervals and downloads the file to our data centre in Port Vila. Every hour Geohazards Division makes available a picture to the Department website (http://www.vmgd.gov.vu/vmgd/index.php/geohazards/volcano).

Our cameras are night-capable, allowing pictures to be taken at night when there is enough light such as when there is a full moon. So, at night we can see the glow from the volcano if it is active enough.

Seismic monitoring of small local earthquakes commonly provides the first indication of volcanic unrest.

In Vanuatu, the Geohazards Division has established seismic sensors on many of the active volcanoes. These include Tanna (Yasur), Ambrym, Ambae and Lopevi. Data from these sensors are sent back to Port Villa 24 hours a day. The public and local community with internet access can see some of the data from theses sensors on the Department web page (http://www.vmgd.gov.vu/vmgd/index.php/geohazards/volcano).

The staff at Geohazards Division look for volcanic earthquakes and volcanic tremor when they analyse the data.

Volcanic Earthquakes are caused when the rocks are broken by the molten rock (magma) moving through them. If the rocks are relatively cool and brittle, then the moving molten rock (magma) will make earthquakes as it breaks through. Sometimes theses can be felt by the local community.

If a flank eruption was going to happen at a large volcano like Ambrym or Ambae we would expect to see these earthquakes.

Volcanic tremors are caused when the hot volcanic gases escape from the molten rock (magma). As they pass through cracks on the way to the surface they cause a small ground vibration. This can be an almost continuous signal. Volcanic tremor can also be caused by the movement of the molten rock (magma) itself through the volcano on its way to the surface. Also, the molten rock (magma) can react with the local ground water, geothermal system or lake water creating a tremor signal.

When steam and water are present we often see volcanic tremor. The escape of the gas can also make the gas plumes you often see from the volcanoes. Often the plume will appear as a light blue or brown colour. The brown colour is not always volcanic ash. Today Geohazards Division can use data from satellites to see the amount of gas from volcanoes.

As Geohazards Division has the capacity to monitor many of the active volcanoes in Vanuatu, the people living nearby are now safer. The Geohazards Division staffs and public can follow the volcanoes activity on the web page (www.vmgd.gov.vu) and Facebook (Vanuatu Geohazards Observatory or Vanuatu Meteorology and Geohazards Department).

Geohazards can be reach through email: geohazards@meteo.gov.vu

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