Volcanoes inspire awe with spectacular eruptions and incandescent rivers of lava, but often their deadliest hazard is what quietly falls from the sky.
When a large volcano erupts, as Mount Spurr appears close to doing about 80 miles from Anchorage, Alaska, it can release enormous volumes of ash. Fine ash can infiltrate the lungs of people and animals who breathe it in, poison crops and disrupt aquatic life. Thick deposits of ash can collapse roofs, cripple utilities and disrupt transport networks.
Ash may lack the visual impact of flowing lava, but as a geologist who studies disasters, I’m aware that ash travels farther, lasts longer and leaves deep scars.
Volcanic ash: What it is, and why it matters
Volcanic ash forms when viscous magma – molten rock from deep beneath Earth’s surface – erupts, exploding into shards of rock, mineral and glass carried in a near-supersonic stream of hot gas.
Towering clouds of ash rise several miles into the atmosphere, where the ash is captured by high-altitude winds that can carry it hundreds or even thousands of miles.
As the volcanic ash settles back to Earth, it accumulates in layers that typically decrease in thickness with distance from the eruption source. Near the vent, the ash may be several feet deep, but communities farther away may see only a dusting.
Breathing danger: Health risks from ash
Breathing volcanic ash can irritate the throat and lungs, trigger asthma attacks and aggravate chronic respiratory conditions such as COPD.
The finest particles pose the greatest risk because they can penetrate deep into the lungs and cause death by asphyxiation in the worst cases. Mild, short-term symptoms often resolve with rest. However, the long-term consequences of ash exposure can include silicosis, a lung disease and a possible cause of cancer.
The danger increases in dry regions where fallen ash can be kicked up into the air again by wind or human activity.
Risks to pets and livestock
Humans aren’t the only ones at risk. Animals experience similar respiratory symptoms to humans.
Domestic pets can develop respiratory distress, eye inflammation and paw irritation from exposure to ash.
During the 2010 Eyjafjallajökull eruption in Iceland, farmers were advised to shelter sheep and cattle because the ash contained fluoride concentrations above the recognized safety threshold of 400 parts per million. Animals that remained exposed became sick and some died.
Harm to crops, soil and water
Soil and crops can also be damaged. Volcanic ash alters the acidity of soil and introduces harmful elements such as arsenic and sulfur into the environment.
While the ash can add nutrients such as potassium and phosphorus that enhance fertility, the immediate impact is mostly harmful.
Ash can smother crops, block sunlight and clog the tiny stomata, or pores, in leaves that allow plants to exchange gases with the atmosphere. It can also introduce toxins that render food unmarketable. Vegetables, fruit trees and vines are particularly vulnerable, but even sturdy cereals and grasses can die if ash remains on leaves or poisons emerging shoots.
Following the 1991 Mount Pinatubo eruption, vast tracts of farmland in central Luzon in the Philippines were rendered unproductive for years due to acidic ash and buried topsoil. If multiple ashfalls occur in a growing season, crop failure becomes a near certainty. It was the cause of a historic famine that followed the eruption of Mount Tambora in 1815.
Ash can ground airplanes, gum up infrastructure
Ash clouds are extremely dangerous to aircraft. The glassy ash particles melt when sucked into jet turbines, clog fuel systems and can stall engines in midair.
In 1982, British Airways Flight 9 lost power in all four engines after flying through an ash cloud. A similar incident occurred in 1989 to KLM Flight 867 over Alaska. In 2010, Iceland’s Eyjafjallajökull eruption grounded more than 100,000 flights across Europe, disrupting travel for over 10 million passengers and costing the global economy billions of dollars.
Volcanic ash can also wreak havoc on infrastructure by clogging water supplies, short-circuiting electrical systems and collapsing roofs under its weight. It can disrupt transportation, communication, rescue and power networks, as the 1991 eruption of Mount Pinatubo in the Philippines dramatically demonstrated.
What to do during ashfall
During an ashfall event, the most effective strategy to stay safe is to stay indoors as much as possible and avoid inhaling ash particles.
Anyone who must go outside should wear a properly fitted N95 or P2 mask. Cloth masks provide little protection against fine ash. Rainwater tanks, troughs and open wells should be covered and monitored for contamination. Livestock should be moved to clean pastures or given uncontaminated fodder.
To reduce structural damage, ash should be cleared from roofs and gutters promptly, especially before rainfall.
Older adults, children and people who are sick are at greatest risk, particularly those living in poorly ventilated homes. Rural communities that are dependent on agriculture and livestock are disproportionately affected by ashfall, as are low-income people who lack access to clean water, protective masks or safe shelter.
Communities can stay informed about ash risks through official alerts, including those from the Volcanic Ash Advisory Centers, which monitor ash dispersion and issue timely warnings. The International Volcanic Health Hazard Network also offers guidelines on personal protection, emergency planning and ash cleanup.
The long tail of ash
Volcanic ash may fall quietly, but its effects are widespread, persistent and potentially deadly. It poses a chronic threat to health, agriculture, infrastructure and aquatic systems.
Recognizing the risk is a crucial first step to protecting lives. Effective planning and public awareness can further help reduce the damage.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Accurate information for Southcentral Alaska, from the Alaska Volcano Observatory
Kristi Wallace, a volcanologist with the Alaska Volcano Observatory, provided the following to give accurate information on ashfall impacts from a Mount Spurr eruption on Southcentral Alaska:
Ashfall on southcentral Alaska from a Spurr eruption, if it were to occur, is expected to be as thick as ¼ inch based on historical eruptions in 1953 and 1992 and geological studies of eruptions over the past many thousands of years. Ashfall would only occur if the winds were blowing from the volcano toward your community during an eruption so it is possible that your community might not get ashfall. Ashfall is expected to fall for a few hours which is considered an acute or short-term exposure and not chronic or long-term. This amount of ash is more of a nuisance than a hazard for most people.
- Volcanic ashfall is not toxic.
- Ashfall is an air quality concern, especially if the particles are very fine-grained — 10 microns or 1/100th of a millimeter, or smaller — so people with existing respiratory or cardiovascular conditions should seek medical guidance regarding risk associated with ashfall. Most impacts can be minimized by reducing exposure to ash and wearing a properly fitted dust mask — N95 or similar — during exposure.
- Silicosis or the lung disease from ash exposure is not a concern for anyone in Alaska because the ash exposure is short term and not over many months or years.
- One-quarter inch of ash will not collapse roofs and it is not recommended to shovel roofs due to the risk of falling off roofs and ladders.
- Ashfall will not contaminate groundwater supplies.
- Ashfall is not expected to impact open water drinking water supplies based on the small amount and the Alaska Department of Environmental Conservation is working with public water facilities to monitor water quality after ashfalls.
- Ashfall is not expected to impact local utilities based on the small amount of ash and all local Southcentral Alaska utilities, such as power, IT, communications, etc., are well informed and have plans in place to minimize impacts to keep services up and running.
- Pets and livestock are not expected to be impacted by ¼ inch of ash. Minimize
exposure during ashfall of a few hours and provide clean drinking water and food. - Ash will not poison crops. Leaf damage can occur from ash leachates, not poisoning.
- One-quarter inch of ash is not expected to have significant loading impacts for most arable crops. Volcanic ash is a natural fertilizer which is why many communities around the world live near volcanoes, where soils are so fertile.
How to get information on volcanic activity and ashfall on my community?
- The best way to get information about the current status of Mount Spurr Volcano is to visit the Alaska Volcano Observatory: avo.alaska.edu/volcano/spurr/activity. You can sign up for AVO volcano notifications here: https://volcanoes.usgs.gov/vns/.
- Official warnings of ashfall on communities and mariners will be issued by the National Weather Service Anchorage Forecast Office, weather.gov/afc, including where and when is it expected to fall, as well as how much is expected to fall.
- Contact your local emergency management office. Some communities offer subscription service for notifications that are delivered electronically. Others will have information on their local emergency management website.
- Information on ashfall impacts and mitigation: volcanoes.usgs.gov/volcanic_ash/ash.html.
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