Volcanic Eruptions


A volcanic eruption is the sudden release of lava, tephra, and gasses from a volcanic vent or fissure.


Many different types of volcanic eruptions are found around the world. The most common types of eruptions are:

These are only a few examples of the types of volcanic eruptions found around the world. Each eruption can vary in strength, time length, and amount of destruction done to the surrounding area. Additionally, what is released with an eruption can vary greatly, with different amounts of tephra, lava, and gases all possible.


Volcanoes form where Earth's plates move away from each other or collide, pushing one plate under the other. This action allows magma (melted mantle material) to flow out onto Earth's surface. Magma can also be released in the middle of a plate, if the magma is unusually hot and can rise to just under the plate's surface. This hot spot, which can be from 310–620 miles (500–1,000 km) wide, remains in one area as the plate continues to move above it, forming a line of volcanoes.

On Thursday, January 25, 2018, the Mayon volcano spews molten lava during its sporadic eruption in the early morning outside Legazpi city, Albay province, around 340 kilometers (200 miles) southeast of Manila, Philippines.

On Thursday, January 25, 2018, the Mayon volcano spews molten lava during its sporadic eruption in the early morning outside Legazpi city, Albay province, around 340 kilometers (200 miles) southeast of Manila, Philippines.
(AP Photo/Bullit Marquez)

The heat of the magma causes solid rock to become liquid, building pressure and forcing the magma upwards. This melts more rock and adds to the amount of magma headed toward Earth's surface. The magma then collects in magma chambers below Earth's surface, where it stays until a crack opens or the pressure becomes great enough to force it out onto the surface of the earth. When this happens, magma becomes lava and it is said that the volcano is erupting. Depending on the type of volcanic eruption, the amount of lava, gas, and tephra (including ash, dust, lapilli, bombs, cinders, and blocks) released will vary.

Not all volcanic eruptions are devastating to the people around them. Volcanic eruptions on the ocean floor allow new crust to form, filling in gaps created by Earth's plates moving away from each other. Other eruptions may take place in sparsely populated or unpopulated areas or lead to the creation of new islands. Lava released from volcanic eruptions can also build on itself, developing larger volcanoes both under water and on Earth's surface.

Risk factors

Volcanoes can be found around the world; however, the most active volcanoes are in the Ring of Fire, an area around the Pacific Ocean where the most volcanic activity occurs. Because of the way volcanoes are formed, the most common areas for volcanic eruptions are along tectonic plates that are either converging (coming together) or diverging (moving away from each other). Scientists and researchers monitor volcanic activity in order to try to predict when a volcanic eruption may occur. Signs of an upcoming eruption may develop months or weeks before the actual eruption. Other times, signs may lead to a false alarm and no eruption takes place. Monitoring volcanic activity allows for the development of early warning systems that can give people the chance to evacuate and prepare for a volcanic eruption.

Effects on public health

On Tuesday, March 6, 2018, a column of volcanic smoke rises from the crater on the Shinmoedake volcano after its eruption in Kirishima, southern Japan. The volcano erupted violently several times Tuesday,

On Tuesday, March 6, 2018, a column of volcanic smoke rises from the crater on the Shinmoedake volcano after its eruption in Kirishima, southern Japan. The volcano erupted violently several times Tuesday, shooting up ash and smoke up to 2,300 meters (7,500 feet) in its biggest explosion since 2011.
(Kyodo News via AP)

The gases released by volcanoes often blow away very quickly, reducing their health threat. The pollution is sometimes called vog, or a volcanic fog. However, people exposed to a large amount of gas, or those who are in an area where the gas does not dissipate quickly, may have difficulty breathing or experience nose, throat, and eye irritation. Common volcanic gases include carbon dioxide, sulfur dioxide, hydrogen chloride, and hydrogen fluoride. People who are exposed to volcanic gases for a longer period may also experience headaches, swelling, dizziness, and suffocation. Suffocation because of volcanic gases is the most common cause of death from a volcanic eruption.

Other health threats from volcanic eruptions include burns, illness, injury, mudslides, floods, drinking water contamination, wildfires, and the spread of infectious diseases. Each volcanic eruption is unique and so are the health threats that go along with it.


People who are in an area affected by a volcanic eruption should try to limit the amount of contact they have with ash and volcanic gases. This can be done by staying indoors or by using an air-purifying respirator. Injuries and burns should be seen by a physician as soon as possible. People who continue to experience headaches, dizziness, or respiratory problems after the initial eruption should also speak to a physician. For the most part, volcanic eruptions do not pose many long-term health threats if precaution is taken, such as not drinking water contaminated with ash and remaining indoors away from the ash and gases.

Public health role and response

Emergency response to a volcanic eruption may begin before the event has even taken place. An early warning system may be used to let citizens know that they need to evacuate from hazard zones and prepare for a potential eruption. People with disabilities or health problems may be evacuated with the help of support organizations or governmental groups. Bottled water and food, which can be stored and prepared without power, may be collected along with emergency supplies, such as first aid kits, flashlights, and air purifying respirators.

After the eruption, emergency personal may take a census of the population and search for people who need medical help. Refuge zones are set up in areas with cleaner air where affected citizens can receive water, food, and medical help. Transportation often is available to help people get to these refuge zones. Security in evacuated areas may also be set up in order to protect the property of those who have left the hazard zones.

Cleanup from a volcanic eruption can take anywhere from a few days to months depending on the amount of devastation. Ash may clog filters, destroy engines, and cause buildings to collapse because of the strain it puts on roofs. Drinking water may be contaminated and power may be out for an extended period. For these reasons, emergency response and refuge zone assistance usually continue well after the initial eruption has taken place.


Most people do not experience any long-lasting health effects after being in an area affected by a volcanic eruption. Symptoms should fade quickly once individuals reach an area where the air is free of volcanic gas and ash. Silicosis cannot currently be cured. Those individuals exposed to silica and diagnosed with the disease should work with their physician to alleviate symptoms and limit complications.

A disease in which the air passages of the lungs become inflamed and narrowed.
Also known as molten rock, lava is magma that has been exposed to the earth's surface through a volcano. Liquid lava can reach temperatures from 1,292 to 2,192°F (700 to 1,200°C). Lava forms rock when cooled.
An extremely hot fluid material found under Earth's crust. When magma hits the surface of the earth, it begins to cool and becomes lava.
A lung disease caused by inhaling silica dust. Silicosis is considered a type of occupational lung disease because it is most often found in people who are working in hard-rock mining, tunneling, quarrying, and other jobs that expose them to silica dust. Natural disasters, such as volcanoes, which cause a large amount of silica dust, can also cause silicosis.
The general term for rock particles and fragments produced by a volcanic eruption.


Although volcanic eruptions cannot be prevented, current technology and careful preparation can reduce the health risks and destruction associated with volcanoes. Volcanos around the world are active and there are many more eruptions than are normally reported, as in the case of the 2018 volcanic activity that occurred in Hawaii, Guatamala, and Indonesia within weeks of each other. The ability for scientists to monitor volcanic activity allows early warning systems to be used and people in high-risk zones are often able to evacuate before an eruption occurs. Additionally, having an emergency plan in place, along with extra food, water, and emergency supplies, such as a first aid kit and air purifying respirators, reduces the risk of injury and long-term negative health effects from ash and volcanic gases.

See also Asthma ; Earthquakes ; Silicosis ; Wildfires .




Kusky, Timothy. Volcanoes: Eruptions and Other Volcanic Hazards. New York: Facts on File, 2008.


Centers for Disease Control and Prevention. “Volcanoes.” http://emergency.cdc.gov/disasters/volcanoes/index.asp (accessed May 9, 2018).

Federal Emergency Management Agency. “Volcanoes.” http://www.ready.gov/volcanoes (accessed May 9, 2018).

How Stuff Works. “How Volcanoes Work.” http://science.howstuffworks.com/nature/natural-disasters/volcano.htm (accessed May 9, 2018).

U.S. Geological Survey. “Current Alerts for U.S. Volcanoes.” http://volcanoes.usgs.gov/activity/status.php (accessed May 9, 2018).


Federal Emergency Management Agency (FEMA), PO Box 10055, Hyattsville, MD, 20782, (202) 646 2500, (800) 621 3362, http://www.fema.gov .

International Union of Geodesy and Geophysics, Hertzstrasse 16, Karlsruhe, Germany, 76187, 49 (721) 60844494, Fax: 49 (721) 711-73, secretariat@iugg.org, http://www.iugg.org .

World Organization of Volcano Observatories, 903 Koyukuk Dr., Fairbanks, AK, 99775, (907) 474-1542, Fax: (907) 474-7290, wovo.iavcei@gmail.com, http://www.wovo.org .

Tish Davidson, AM

  This information is not a tool for self-diagnosis or a substitute for professional care.