Volcanic hazards and impact

Volcanic hazards

A Volcanic hazard is any potentially dangerous volcanic phenomenon or process that may cause loss of life, injury or other health impacts, property damage, social and economic disruption or environmental degradation. Volcanic hazards occur before, during and after volcanic eruptions.

Most volcanoes have episodes of volcanic unrest when there are signs at the Earth’s surface of the movement of magma and/or fluids in the subsurface. Volcanic hazards associated with unrest may include felt earthquakes, ground fracturing, ground uplift or subsidence, gas emissions and steam explosions. Many volcanoes are monitored using a range of instruments so scientists can attempt to anticipate if or when magma may reach the surface. Monitoring may lead to mitigation actions by civil protection agencies such as temporary evacuation.

A volcanic eruption can be devastating. Large explosive eruptions send columns of volcanic ash and gas high into the atmosphere, and if the ash column collapses, pyroclastic flows (pyroclastic density currents) are formed which sweep down the flanks of the volcano. Ballistic rocks and bombs can be blasted several kilometres from the eruption vent. Sometimes the partial collapse of a lava dome or cone generates fast-moving, highly mobile pyroclastic flows and surges that are not confined to valleys and can even travel uphill (e.g. Unzen volcano, 1991; Soufriere Hills Volcano, Montserrat 1997). Lava flows can engulf villages and destroy roads, for example as during the May-June 2018 eruption in Hawaii. Lahars are hot or cold mixtures of volcanic debris and water that flow down valleys. Volcanic eruptions can last from hours to days, weeks to years and may show a great variety of types of behaviour and diverse hazards.

After an eruption, heavy rainfall will continue to generate lahars as long as loose volcanic debris and ash is on the ground. Lahars continued for decades after the 1991 Pinatubo eruption in the Philippines.

To understand volcanic hazards around a particular volcano it is important to:

  • Document the past behaviour of the volcano through geological and geochronological studies
  • Calculate the frequency and magnitude of past eruptions and consider what may be possible in future
  • Monitor and analyse volcanic activity using multiple methods to enable eruption forecasting
  • Run models to investigate dynamic hazardous processes and generate hazards maps
  • Have access to high spatial and temporal resolution Earth Observation products

Volcanic impacts

The impacts of volcanic hazards can be far-reaching, with disruptive ash fall or lahars affecting areas tens to hundreds of kilometres from the volcano. Aviation disruption can have even wider impacts (e.g. Eyjafjallajökull 2010).

Pyroclastic density currents and lahars have caused most fatalities (50%) in historical times (since 1600AD), followed by indirect causes such as famine and disease (24%). About 58% of fatalities in historical times have been caused by just five catastrophic eruptions, each claiming tens of thousands of lives. Notably these were not all large magnitude eruptions.

On the 3rd June 2018, the Volcán de Fuego in Guatemala exploded sending fast-moving pyroclastic density currents down the flanks of the volcano, spilling out of valleys and across populated areas, killing over 150 people and leading to displacement and disruption.

Assessing the damage and impacts after an eruption is an important part of learning lessons and preparing better for future events.

Our research

Our research contributes to understanding of volcanic processes and phenomena and understanding of volcanic hazards and risk, we support planning, preparation, effective response to and recovery from volcanic eruptions.

Research Projects

RiftVolc RiftVolc

Rift Volcanism: past, present, future

East African Rift STREVA

Strengthening Resilience in Volcanic Areas


European Network of Observatories and Research Infrastructures for Volcanology

As well as research projects, we are also involved in commercial projects which underpins our research in Africa, Asia and Latin America, some of which include:


Collaborative Risk Assessment for Volcanoes and Earthquakes


Global Facility for Disaster Reduction and Recovery Challenge Fund


Auker, M. R., R. S. J. Sparks, L. Siebert, H. S. Crosweller and J. Ewert (2013). "A statistical analysis of the global historical volcanic fatalities record." Journal of Applied Volcanology 2(1): 2.

National Coordinator for Disaster Reduction, Guatemala (CONRED)

Philippine Institute of Volcanology and Seismology (PHIVOLCS)

The Encyclopedia of Volcanoes (Second Edition), H. Sigurdsson. Amsterdam, Academic Press

United Nations Office for Disaster Risk Reduction (UNISDR) annual report 2017

Sendai Framework for Disaster Risk Reduction (SFDRR) 2015