Volcanic hazards and impact

Ash pouring from Iceland's Eyjafjallajökull volcano in 2010 (Images & caption courtesy of NASA).

Volcanic hazards encompass all threat relating to an eruption including direct threat to life and infrastructure and threat from related phenomena such as mudflows and floods.

For communities living around a volcano, an eruption can be catastrophic. Lava flows can engulf villages and destroy roads, for example in Hawaii and Laki in Iceland. 

Large explosive eruptions send ash and gas high into the atmosphere, and when the ash column collapses, pyroclastic flows are formed which sweep down the flanks of the volcano destroying everything in their path.


After an explosive eruption, large amounts of ash blankets the area, which can cause roofs to collapse. During periods of sustained rainfall mudflows or lahars can form, which are incredibly destructive, burying towns and villages.

When Nevado Del Ruiz volcano, in Columbia, erupted in 1985, it melted ice from the glacier which sat on top of the volcano, creating giant mudflows which destroyed towns and villages killing more than 23 000 people.

Gas release

Along with ash, large volumes of gases are released into the atmosphere.  During the 1783–84 eruption of the Laki fissure in Iceland, emissions of gases resulted in stunting the growth of crops, causing famine and the death of about 70% of Iceland's livestock and about 20% of Iceland's human population.

But volcanic eruptions not only pose a direct threat to life, they also pose an indirect threat to local (and global) infrastructure. Eruptions can cause loss of livelihoods through the destruction of crops, buildings (hospitals, schools, offices and homes) and water supplies.

Ash clouds

Volcanic eruptions are also a global hazard. As we saw in 2010 with the eruption of Eyjafjallajökull, Icleand, ash clouds can have large impacts on the aviation industry. The Eyjafjallajökull eruption resulted in the closure of airspace over northern Europe for ten days, impacting hundreds of thousands of people globally, and resulting in financial losses of millions of pounds.


Eruptions occurring on volcanic islands can produce tsunamis with devastating effects reaching tens or hundreds of kilometres away.

Understanding volcanic hazards and impact

The impact of a volcanic eruption depends on a number of factors relating to the volcano. For example,

  • magnitude of the eruption
  • type of eruption
  • magma composition
  • location of the volcano
  • secondary factors; such as wind direction, rainfall and local population

In understanding volcanic hazards and assessing the risks of a particular volcano it is important to understand the volcanic system:

  • knowing the past behaviour of the volcano
  • monitoring the current activity
  • working with local communities;
    to develop an understanding of the local infrastructure to effectively communicate the risks and to help communities prepare for and recover from a volcanic eruption

Research Projects

East African RiftSTREVA

Strengthening Resilience in Volcanic Areas


For more information on volcanic hazards and impacts, please contact Dr Sue Loughlin or Dr Julia Crummy