Volcanic Eruption

The Operational Land Imager (OLI) on the Landsat 8 satellite acquired this top image of Mount Etna on December 28, 2018. The image highlights the active vent and thermal infrared signature from lava flows, which can be seen near the newly formed fissure on the southeastern side of the volcano. The image was created with data from OLI (bands 4-3-2) and the Thermal Infrared Sensor (TIRS) on Landsat 8. Image: NASA.


A type of volcanic event near an opening/vent in the Earth’s surface including volcanic eruptions of lava, ash, hot vapour, gas, and pyroclastic material (IRDR Glossary).

The majority of volcanoes in the world form along the boundaries of Earth's tectonic plates. When tectonic plates collide, one often plunges deep below the other in what's known as a subduction zone. Not all volcanoes are related to subduction: another way volcanoes can form is what's known as hotspot volcanism. In this situation, a zone of magmatic activity—or a hotspot—in the middle of a tectonic plate can push up through the crust to form a volcano. Although the hotspot itself is thought to be largely stationary, the tectonic plates continue their slow march, building a line of volcanoes or islands on the surface (National Geographic).

A volcano is currently active if it is erupting lava, releasing gas or generating seismic activity. An active volcano is labelled dormant if it has not erupted for a long time but could erupt again in the future. When a volcano has been dormant for more than 10 000 years, it is considered extinct. Volcanoes can remain inactive, or dormant, for hundreds or thousands of years before erupting again. During this time, they can become covered by vegetation, making them difficult to identify.

How explosive a volcanic eruption is depends on how easily magma can flow or trap gas. If magma is able to trap a large amount of gas, it can produce explosive eruptions.  (Australian Government).


Facts and figures

Over the last 11,500 years, more than 1,500 major eruptions have occurred, with approximately 500 in the Pacific "Ring of Fire" alone (PreventionWeb).

There are volcanoes on every continent, even Antarctica. Some 1,500 volcanoes are still considered potentially active around the world today; 161 of those—over 10 percent—sit within the boundaries of the United States (National Geographic).

There are different types of eruptive events. We can distinguish between primary and secondary events.

Primary events are:

  • Pyroclastic explosions
  • Hot ash releases
  • Lava flows
  • Gas emissions
  • Glowing avalanches (gas and ash releases)

Secondary events are:

  • Melting ice, snow and rain accompanying eruptions are likely to provoke floods and hot mudflows (or lahars)
  • Hot ash releases can start fires (WHO).

Volcanoes can have many different appearances. The shape of a volcano provides clues to the type and size of eruption that occurred. Eruption types and sizes depend on what the magma is made up of. Three common volcano forms are:

  1. Shield volcano: have a broad, flattened dome-like shape created by layers of hot and runny lava flowing over its surface and cooling.
  2. Composite volcano : also known as stratovolcanoes, they are formed from explosive eruptions. These eruptions create steep sided cones.
  3. Caldera volcano: these volcanoes erupt so explosively that little material builds up near the vent. Eruptions partly or entirely empty the underlying magma chamber which leaves the region around the vent unsupported, causing it to sink or collapse under its own weight. The resulting basin-shaped depression is roughly circular and is usually several kilometres or more in diameter (Australian Government).

Related content on the Knowledge Portal


A photo of Mt. Etna erupting on 30 October 2002, taken by astronauts aboard the International Space Station. Image: NASA Earth Observatory/Earth Sciences and Image Analysis Laboratory at Johnson Space Center.

“More than half of the world’s active volcanoes are not monitored instrumentally,” according to GFZ Helmholtz Centre Potsdam. Yet eruptions occur quite frequently, with up to 85 of the 1500 active volcanoes erupting each year, and can cause significant damage. For example, the 2018 volcanic eruptions at Fuego (Guatemala) and Anak Krakatau (Indonesia) resulted in 430 dead and missing persons. This threat to human life makes improving the monitoring of volcanoes all the more important. 

A German research team, made up of scientists  from the Technical University of Berlin and the GFZ German Research Centre for Geosciences in Potsdam,... read more

Publishing date: 06/08/2019
Damage from a 7.4 earthquake and a tsunami that hit the Indonesian island of Sulawesi on 28 September 2018. Image: European Union/Pierre Prakash/Flickr.

In the past year, “there were 315 natural disaster events recorded with 11,804 deaths, over 68 million people affected, and US$131.7 billion in economic losses around the world.” This is according to the Centre for Research on the Epidemiology of Disasters (CRED) in its recently released 2018 Natural Disasters Report

While these 2018 natural disaster values represent a decrease when compared with the annual averages from 2008 to 2017, some geographic areas still experienced great losses of life and damages due to natural hazards. Indonesia was most adversely impacted in terms of lives claimed, with earthquakes in August and September 2018 that left a total of 4,904 people dead or missing, according to the CRED. Earthquakes also accounted for the greatest number of deaths among natural disasters worldwide in 2018. And among all types of natural hazards, floods affected the greatest number of people during the past... read more

Publishing date: 01/07/2019
Gas emissions at Volcán Copahue, captured on January 5, 2013 using EO-1 ALI data from the NASA EO-1 team.

To predict when a volcano will erupt, researchers rely on indirect signals. However, without long-term and ground-based observations, it is difficult to determine whether these signals are normal disturbances or indicators of a looming eruption. New research suggests satellite data could help to fill that gap and improve scientists understanding of the complex warning signs a volcano may issue before it erupts.

The multidecadal study analyzed 17 years of remote sensing observations of 47 volcanoes in Latin America, where more than 60 per cent of active volcanoes are unmonitored. The researchers looked at three types of data: sulfur dioxide gas emissions, which often increase before a volcano erupts; thermal measurements and radar data that show how a volcano is changing shape.

On the basis of their analysis of the satellite data, the team found that the majority of the 47 volcanoes were on a spectrum between open systems, able to release... read more

Publishing date: 04/04/2019

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The team of experts led by UN-SPIDER is conducting multiple activities and institutional visits in Lima. The team is comprised of eight experts from UN-SPIDER; the German Aerospace Centre (DLR); the Argentinian National Space Activities Commission (CONAE); the Mexican Space Agency (AEM); the Agustin Codazzi Geographic Institute of Colombia (IGAC); the Santa... read more

Publishing date: 01/04/2019
Bali, Indonesia. Mount Agung eruption. False color image. 28 November 2017. Based on Sentinel-3 data.

A team of scientists, led by the University of Bristol’s School of Earth Sciences, has used Sentinel-1 satellite imagery to analyze the ground deformation of the Agung volcano in Bali, Indonesia, and explain why it erupted in November 2017 after 50 years of dormancy.

The previous eruption of Agung in 1963 killed nearly 2,000 people and was followed by a small eruption of its neighbouring volcano, Batur. Because this past event was among the deadliest volcanic eruptions of the 20th century, the scientific community deployed a great effort into the monitoring and understanding of the re-awakening of Agung.

Two months before the eruption, a sudden increase in the number of small earthquakes occurred around the volcano. The researchers realized satellite images could reveal the volcanic ground deformation that occurred prior to the 2017 eruption. From satellite imagery and 3D numerical models, they were able to show that this continuous... read more

Publishing date: 06/03/2019

Data Source

Publishing institution: National Aeronautics and Space Administration (NASA)
Based on MODIS data, MIROVA detects near real time volcanic hot spots. In order to do so MIROVA analyses the MiddleInfraRed Radiation (MIR) measured over large volcanoes to detect, locate and measure the heat radiation from volcanic activity. This automated thermal monitoring of the most active volcanoes on Earth in near real time provides the user with a quick overview of the latest thermal images which are available for Google Earth overlapping. Additionally, MIROVA provides an updated Volcanic Radiative Power (VRP) time-series in logarithmic and normal scale. MIROVA has been developed as a collaboration between the University of Turin and the University of Florence.
Publishing institution: Copernicus
Monitoring Unrest From Space (MOUNTS) is a monitoring system for volcanoes worldwide using Sentinel-1 (SAR), Sentinel-2 (SWIR) and Sentinel-5P (TROPOMI) data. The project focuses on calculating parameters which can inform on the state of the volcanic activity. It was developed by a collaboration of Technical University Berlin (TU-Berlin) and the German Research Centre for Geosciences (GFZ) with funding by GEO.X.
Publishing institution: Smithsonian Institution - National Museum of Natural History
The Global Volcanism Program database currently contains 1432 volcanoes with eruptions during the Holocene period (approximately the last 10,000 years). Primary names are sorted below in alphabetical order. Please use the volcano search page to find other names and create a list with synonyms and subfeatures.


The free online course, provided by the University of Iceland, gives an introduction to volcano monitoring techniques, magma movements and volcano unrest. It presents some aspects of why volcanoes are dangerous and volcanic hazards. The course starts on 4 March 2019 and lasts for six weeks.

As magma, molten rock inside volcanoes, approaches the surface it releases volcanic gas that finds its way to the surface, and geothermal activity can change.  In addition to ground-based techniques, satellite observations are extensively used. The main monitoring techniques for volcanoes are explained in the course, with the aim that students understand both the concept of volcanic unrest and how it can be monitored, how eruptions can be monitored, and signs of volcanic eruptions as seen on instruments.

Understanding the possibilities and limitations of present-day volcano monitoring for detecting magma movements is an... read more


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