David Kitchen, University of Richmond 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.

Livestock face greater dangers. If grazing animals eat volcanic ash, it can damage their teeth, block their intestines and poison them. 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 also contaminate surface water by introducing toxins and increasing the water’s acidity. The toxins can leach into groundwater, contaminating wells. Fine ash particles can also settle in waterways and smother aquatic plants and animals. During the 2008 Chaitén eruption in Chile, ash contamination led to widespread fish deaths in the Río Blanco.

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. David Kitchen, Associate Professor of Geology, University of Richmond This article is republished from The Conversation under a Creative Commons license. Read the original article.

Jonathan P. Stewart, University of California, Los Angeles and Lucy Arendt, St. Norbert College Earthquakes and the damage they cause are apolitical. Collectively, we either prepare for future earthquakes or the population eventually pays the price. The earthquakes that struck Myanmar on March 28, 2025, collapsing buildings and causing more than 3,000 deaths, were a sobering reminder of the risks and the need for preparation. In the U.S., this preparation hinges in large part on the expertise of scientists and engineers in federal agencies who develop earthquake hazard models and contribute to the creation of building codes designed to ensure homes, high-rises and other structures won’t collapse when the ground shakes. Local communities and states decide whether to adopt building code documents. But those documents and other essential resources are developed through programs supported by federal agencies working in partnership with practicing engineers and earthquake experts at universities. This essential federal role is illustrated by two programs that we work closely with as an earthquake engineer and a disaster management expert whose work focuses on seismic risk.

Improving building codes

First, seismologists and earthquake engineers at the U.S. Geological Survey, or USGS, produce the National Seismic Hazard Model. These maps, based on research into earthquake sources such as faults and how seismic waves move through the earth’s crust, are used to determine the forces that structures in each community should be designed to resist. A steering committee of earthquake experts from the private sector and universities works with USGS to ensure that the National Seismic Hazard Model implements the best available science.

Second, the Federal Emergency Management Agency, FEMA, supports the process for periodically updating building codes. That includes supporting the work of the National Institute of Building Sciences’ Provisions Update Committee, which recommends building code revisions based on investigations of earthquake damage. More broadly, FEMA, the USGS, the National Institute of Standards and Technology and the National Science Foundation work together through the National Earthquake Hazards Reduction Program to advance earthquake science and turn knowledge of earthquake risks into safer standards, better building design and education. Some of those agencies have been threatened by potential job and funding cuts under the Trump administration, and others face uncertainty regarding continuation of federal support for their work. It is in large part because of the National Seismic Hazard Model and regularly updated building codes that U.S. buildings designed to meet modern code requirements are considered among the safest in the world, despite substantial seismic hazards in several states. This paradigm has been made possible by the technical expertise and lack of political agendas among the federal staff. Without that professionalism, we believe experts from outside the federal government would be less likely to donate their time. The impacts of these and other programs are well documented. We can point to the limited fatalities from U.S. earthquakes such as the 1989 Loma Prieta earthquake near San Francisco, the 1994 Northridge earthquake in Los Angeles and the 2001 Nisqually earthquake near Seattle. Powerful earthquakes in countries lacking seismic preparedness, often due to lack of adoption or enforcement of building codes, have produced much greater devastation and loss of life.

The US has long relied on people with expertise

These programs and the federal agencies supporting them have benefited from a high level of staff expertise because hiring and advancement processes have been divorced from politics and focused on qualifications and merit. This has not always been the case. For much of early U.S. history, federal jobs were awarded through a patronage system, where political loyalty determined employment. As described in “The Federal Civil Service System and The Problem of Bureaucracy,” this system led to widespread corruption and dysfunction, with officials focused more on managing quid pro quo patronage than governing effectively. That peaked in 1881 with President James Garfield’s assassination by Charles Guiteau, a disgruntled supporter who had been denied a government appointment. The passage of the Pendleton Act by Congress in 1883 shifted federal employment to a merit-based system. This preference for a merit-based system was reinforced in the Civil Service Reform Act of 1978. It states as national policy that “to provide the people of the United States with a competent, honest, and productive workforce … and to improve the quality of public service, Federal personnel management should be implemented consistent with merit system principles.” The shift away from a patronage system produced a more stable and efficient federal workforce, which has enabled improvements in many critical areas, including seismic safety and disaster response.

Merit-based civil service matters for safety

While the work of these federal employees often goes unnoticed, the benefits are demonstrable and widespread. That becomes most apparent when disasters strike and buildings that meet modern code requirements remain standing. A merit-based civil service is not just a democratic ideal but a proven necessity for the safety and security of the American people, one we hope will continue well into the future. This can be achieved by retaining federal scientists and engineers and supporting the essential work of federal agencies. This article, originally published March 31, 2025, has been updated with the rising death toll in Myanamar. Jonathan P. Stewart, Professor of Engineering, University of California, Los Angeles and Lucy Arendt, Professor of Business Administration Management, St. Norbert College This article is republished from The Conversation under a Creative Commons license. Read the original article.