What you need to know about volcanic ash
By
Brian Lada, AccuWeather meteorologist
Updated Apr 16, 2021 5:19 PM EST
When a volcano erupts, it emits gases, molten rock and particles of rock and glass. Those particles, volcanic ash, can have long-term effects on the surrounding environment and people.
A volcanic eruption is one of the most powerful forces in nature, a seemingly unstoppable phenomenon that can have far-reaching impacts far beyond the area surrounding the volcano itself.
When a volcano erupts, many people think of lava spewing and oozing out of the ground and flowing through the nearby landscape, destroying everything in its path and re-shaping the landscape forever. However, this is not the biggest danger brought on by a volcano.
“Volcanic-ash hazards are far-reaching and disruptive, affecting more people, infrastructure, and daily activities than any other eruptive phenomena,” the United States Geological Survey (USGS) said.
Very fine grains of ash can be ejected tens of thousands of feet into the sky during a major eruption, but closer to the volcano, it can rain down like heavy snow that never melts.
The ash is typically made up of microscopic pieces of rock fragments, volcanic glass or a variety of minerals that do not dissolve in water.
“Falling ash can turn daylight into complete darkness,” the USGS said. “Many people describe the experience as eerie and frightening, disorienting and confusing, or dreadful.”
A 2011 eruption of Shinmoedake, Japan, that spewed ash across the region. (Image/USGS)
In extreme cases, this ash can pile up so much that it is measured in feet. In 1984, Rabaul, Papua New Guinea, was buried in volcanic ash that solidified cars in place and weighed down roofs to the point of collapse.
However, only a fraction of an inch of ash accumulation is needed to impact crops, livestock and infrastructure and require widespread clean-up. These issues can be compounded when it rains, particularly when ash falls on towns and cities as wet ash can conduct electricity, increasing the risk of a fire sparking.
Although it might look like ash from burned wood, volcanic ash is a very different substance.
"Though called ash, volcanic ash is not the product of combustion, like the soft fluffy material created by burning wood, leaves, or paper. Volcanic ash is a hard rain of rough particles. It does not dissolve in water, is extremely abrasive and mildly corrosive, and conducts electricity when wet," the USGS explained.
Volcanic ash accumulates on buildings, and its weight can cause roofs to collapse. A dry layer of ash 4 inches thick weighs 120 to 200 pounds per square yard, and wet ash can weigh twice as much.
Ash buries cars and buildings after the 1984 eruption of Rabaul, Papua New Guinea. (Image/USGS)
On top of the weight, ash can quickly clog up ventilation systems and require people to frequently change the face mask that they are using to prevent inhaling the debris and to slow the spread of the coronavirus.
Depending on the wind, the ash can cause significant disruptions not only in the areas immediately surrounding the volcano, but hundreds or even thousands of miles away.
Following the volcanic eruption on the Caribbean island of St. Vincent, winds blowing to the east sent clouds of ash over Barbados, located more than 100 miles east of the La Soufrière volcano.
People in Barbados were told to stay indoors due to the poor air quality with some residents describing the ash as “falling like snow.” Wearing a mask when outside is also recommended, in addition to helping protect against COVID-19 infection.
A satellite image from Saturday, April 10, shows an ash cloud from the La Soufrière volcano spreading eastward across Barbados. (Image/NASA Worldview)
Even when there is not a dense cloud of ash raining from the sky, the fine particles in the atmosphere can create chaos.
In 2010, air travel was shut down across much of Europe for an entire week after Eyjafjallajökull erupted in Iceland, sending a cloud of hazardous material over the continent.
Commercial airlines had to ground all of their planes that used jet engines as the very fine ash could get into the engines and cause them to stall, potentially causing the plane to crash, Science Magazine explained.
On a much larger scale, a significant, long-duration eruption could spew enough debris into the atmosphere to affect temperatures around the globe.
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In the wake of a major volcanic eruption, the settled ash, along with other volcanic rock and rubble, can set the stage for a potentially disastrous weather-induced event known as a lahar.
Lahars are essentially large debris flows in which rock, mud and water tumble down a steep mountainside, sweeping away everything in their path.
“Volcanoes are a perfect setting for these events because of an abundance of steep, rocky rubble and a ready source of water in the form of rain, snow or ice,” the USGS explained.
About two years after Mount St. Helens cataclysmically erupted in 1980, a lahar was triggered near the mouth of the volcano that gushed downhill and eventually came to a stop 50 miles away, wiping out everything in its path.
The lahar flowed from the crater of Mount St. Helens into the North Fork Toutle River valley and eventually reached the Cowlitz River 80 km (50 mi) downstream. The lahar also entered Spirit Lake, which can be seen in the lower left corner. (Image/ USGS / Casadevall, Tom.)
Not all lahars are this big, and they can occur while a volcano is still erupting.
During the La Soufrière eruption on the island of St. Vincent, a dry river bed was filled with mud and debris from a lahar.
Bridge destroyed by lahar in North Fork Toutle River during eruption of Mount St. Helens, May 18, 1980. (Image/USGS/Waitt, Richard)
Folks that live in close proximity to a volcano should be prepared for both the long-lasting impacts of ashfall and the potential for lahars flowing off the steep terrain.
The USGS recommends people stay indoors to avoid exposure to ash, especially those with pre-existing respiratory conditions.
People that must travel outside amid the ash, even if it has settled on the ground and is no longer falling from the sky, should wear a face mask, pants, a long-sleeve shirt and goggles.
Air quality fluctuations due to volcanic activity, wildfires or any other phenomenon can be seen on AccuWeather’s air quality forecast page by clicking here.
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier, Spectrum, FuboTV, Philo, and Verizon Fios.
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News / Severe Weather
What you need to know about volcanic ash
By Brian Lada, AccuWeather meteorologist
Updated Apr 16, 2021 5:19 PM EST
When a volcano erupts, it emits gases, molten rock and particles of rock and glass. Those particles, volcanic ash, can have long-term effects on the surrounding environment and people.
A volcanic eruption is one of the most powerful forces in nature, a seemingly unstoppable phenomenon that can have far-reaching impacts far beyond the area surrounding the volcano itself.
When a volcano erupts, many people think of lava spewing and oozing out of the ground and flowing through the nearby landscape, destroying everything in its path and re-shaping the landscape forever. However, this is not the biggest danger brought on by a volcano.
“Volcanic-ash hazards are far-reaching and disruptive, affecting more people, infrastructure, and daily activities than any other eruptive phenomena,” the United States Geological Survey (USGS) said.
Very fine grains of ash can be ejected tens of thousands of feet into the sky during a major eruption, but closer to the volcano, it can rain down like heavy snow that never melts.
The ash is typically made up of microscopic pieces of rock fragments, volcanic glass or a variety of minerals that do not dissolve in water.
“Falling ash can turn daylight into complete darkness,” the USGS said. “Many people describe the experience as eerie and frightening, disorienting and confusing, or dreadful.”
A 2011 eruption of Shinmoedake, Japan, that spewed ash across the region. (Image/USGS)
In extreme cases, this ash can pile up so much that it is measured in feet. In 1984, Rabaul, Papua New Guinea, was buried in volcanic ash that solidified cars in place and weighed down roofs to the point of collapse.
However, only a fraction of an inch of ash accumulation is needed to impact crops, livestock and infrastructure and require widespread clean-up. These issues can be compounded when it rains, particularly when ash falls on towns and cities as wet ash can conduct electricity, increasing the risk of a fire sparking.
Although it might look like ash from burned wood, volcanic ash is a very different substance.
"Though called ash, volcanic ash is not the product of combustion, like the soft fluffy material created by burning wood, leaves, or paper. Volcanic ash is a hard rain of rough particles. It does not dissolve in water, is extremely abrasive and mildly corrosive, and conducts electricity when wet," the USGS explained.
Volcanic ash accumulates on buildings, and its weight can cause roofs to collapse. A dry layer of ash 4 inches thick weighs 120 to 200 pounds per square yard, and wet ash can weigh twice as much.
Ash buries cars and buildings after the 1984 eruption of Rabaul, Papua New Guinea. (Image/USGS)
On top of the weight, ash can quickly clog up ventilation systems and require people to frequently change the face mask that they are using to prevent inhaling the debris and to slow the spread of the coronavirus.
Related:
Depending on the wind, the ash can cause significant disruptions not only in the areas immediately surrounding the volcano, but hundreds or even thousands of miles away.
Following the volcanic eruption on the Caribbean island of St. Vincent, winds blowing to the east sent clouds of ash over Barbados, located more than 100 miles east of the La Soufrière volcano.
People in Barbados were told to stay indoors due to the poor air quality with some residents describing the ash as “falling like snow.” Wearing a mask when outside is also recommended, in addition to helping protect against COVID-19 infection.
A satellite image from Saturday, April 10, shows an ash cloud from the La Soufrière volcano spreading eastward across Barbados. (Image/NASA Worldview)
Even when there is not a dense cloud of ash raining from the sky, the fine particles in the atmosphere can create chaos.
In 2010, air travel was shut down across much of Europe for an entire week after Eyjafjallajökull erupted in Iceland, sending a cloud of hazardous material over the continent.
Commercial airlines had to ground all of their planes that used jet engines as the very fine ash could get into the engines and cause them to stall, potentially causing the plane to crash, Science Magazine explained.
On a much larger scale, a significant, long-duration eruption could spew enough debris into the atmosphere to affect temperatures around the globe.
CLICK HERE FOR THE FREE ACCUWEATHER APP
In the wake of a major volcanic eruption, the settled ash, along with other volcanic rock and rubble, can set the stage for a potentially disastrous weather-induced event known as a lahar.
Lahars are essentially large debris flows in which rock, mud and water tumble down a steep mountainside, sweeping away everything in their path.
“Volcanoes are a perfect setting for these events because of an abundance of steep, rocky rubble and a ready source of water in the form of rain, snow or ice,” the USGS explained.
About two years after Mount St. Helens cataclysmically erupted in 1980, a lahar was triggered near the mouth of the volcano that gushed downhill and eventually came to a stop 50 miles away, wiping out everything in its path.
The lahar flowed from the crater of Mount St. Helens into the North Fork Toutle River valley and eventually reached the Cowlitz River 80 km (50 mi) downstream. The lahar also entered Spirit Lake, which can be seen in the lower left corner. (Image/ USGS / Casadevall, Tom.)
Not all lahars are this big, and they can occur while a volcano is still erupting.
During the La Soufrière eruption on the island of St. Vincent, a dry river bed was filled with mud and debris from a lahar.
Bridge destroyed by lahar in North Fork Toutle River during eruption of Mount St. Helens, May 18, 1980. (Image/USGS/Waitt, Richard)
Folks that live in close proximity to a volcano should be prepared for both the long-lasting impacts of ashfall and the potential for lahars flowing off the steep terrain.
The USGS recommends people stay indoors to avoid exposure to ash, especially those with pre-existing respiratory conditions.
People that must travel outside amid the ash, even if it has settled on the ground and is no longer falling from the sky, should wear a face mask, pants, a long-sleeve shirt and goggles.
Air quality fluctuations due to volcanic activity, wildfires or any other phenomenon can be seen on AccuWeather’s air quality forecast page by clicking here.
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier, Spectrum, FuboTV, Philo, and Verizon Fios.
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