Volcanic Activity

Q: How do I protect myself from volcanic ashfall?

Volcanic ash is not like wood ash — it's pulverized rock and glass. Protection is critical: Indoors: Close all windows, doors, and fireplace dampers Seal gaps with damp towels or plastic sheeting and tape Turn off HVAC systems — ash will destroy them and contaminate indoor air Cover electronics and sensitive equipment If you must go outside: Wear N95 or P100 respirator mask (not a cloth mask — ash particles are too fine) Wear airtight goggles (not ventilated) Cover all exposed skin — long sleeves, pants, gloves Limit time outdoors to minimum necessary Cleanup: Dampen ash before sweeping. Never use leaf blowers. Bag ash for disposal — don't wash into storm drains.

Q: What is a lahar and how dangerous is it?

A lahar is a volcanic mudflow — one of the deadliest volcanic hazards: Made of volcanic debris mixed with water (from melted snow, crater lakes, or rain) Travels 20-40+ mph down river valleys — faster than you can run Consistency of wet concrete — it buries and encases everything in its path Can travel 50+ miles from a volcano along river channels Can occur during eruption or days/weeks/months later when rain mobilizes ash deposits The 1985 Nevado del Ruiz lahar in Colombia killed 23,000 people in the town of Armero, 45 miles from the volcano. Protection: Stay out of river valleys near volcanoes. If you hear a roaring sound from a valley, move to high ground immediately. Lahar warning systems exist near some volcanoes — know your local alerts.

Q: How far can volcanic ash travel?

Volcanic ash can travel thousands of miles from an eruption: Near the volcano (0-50 miles): Heavy ashfall. Inches to feet of accumulation. Roof collapse risk. Complete darkness during daylight. Regional (50-300 miles): Moderate ashfall. Visibility reduced. Airport closures. Respiratory hazard. Continental (300-1000+ miles): Light ashfall or haze. Air quality impacts. Aviation disruption. Global: Major eruptions inject ash into the stratosphere. The 1991 Pinatubo eruption cooled global temperatures by 1°F for a year. Even light ashfall is hazardous: it clogs engines, scratches windshields, contaminates water supplies, and damages electronics. The 2010 Eyjafjallajökull eruption in Iceland shut down European air travel for a week — and that was a relatively small eruption.

Q: Is volcanic ash dangerous to breathe?

Yes, extremely. Volcanic ash is microscopic glass and rock fragments: Particles are sharp and abrasive — they cut and irritate lung tissue Fine ash (PM2.5 and smaller) reaches deep into lungs Short exposure: coughing, throat irritation, eye pain Prolonged exposure: silicosis (permanent lung scarring), bronchitis, worsened asthma People with asthma, COPD, or heart conditions are at highest risk Protection: N95 or P100 respirator is the minimum (cloth masks are insufficient) Stay indoors with windows sealed during active ashfall Dampen ash before disturbing it to prevent it becoming airborne Seek medical attention for persistent coughing, wheezing, or breathing difficulty Children and elderly are most vulnerable. Keep them indoors during any ashfall event.

Q: What should I do if a volcano near me erupts?

Immediate actions during a volcanic eruption: If evacuation is ordered: Leave immediately — pyroclastic flows move at 100+ mph and are unsurvivable Take go-bag, medications, pets, and important documents Follow designated evacuation routes — AWAY from river valleys (lahar paths) Do NOT return until authorities give all-clear If sheltering in place (ashfall only, no flow/lahar risk): Close and seal all windows, doors, and vents Turn off HVAC systems Stay inside — wear N95 mask if you must go out Monitor radio/phone for updates — eruptions can escalate quickly Keep water containers covered (ash contaminates water) Clear heavy ash from roof to prevent collapse (wet ash is very heavy) After eruption subsides: continue wearing mask during cleanup. Watch for lahars for weeks/months — rain on ash creates mudflows.

Volcanic eruptions can send ash 100,000 feet into the atmosphere and lahars down valleys at 40 mph

8 things to do before · 8 steps during · 8 after · 5 questions answered

Last updated 2026-09-25. Written by Project Trinetra, a program of the 501(c)(3) nonprofit Unravel The Love. It is not an official government publication and does not replace instructions from your local emergency authorities.

See current conditions. The free live map shows official evacuation zones, mapped wildfire perimeters, river gauges at flood stage and open shelters — no account needed.

Open the live map

Before — Prepare for Volcanic Activity

Volcanic hazards include ashfall, lava flows, pyroclastic flows, lahars (volcanic mudflows), and toxic gases.

#	Do this
1	Know if you live in a volcanic hazard zone (check USGS volcano maps)
2	Stock N95/P100 masks — volcanic ash is microscopic glass that damages lungs
3	Keep airtight goggles available — ash irritates and scratches eyes
4	Store extra water — ashfall contaminates water supplies
5	Plan evacuation routes AWAY from valleys (lahars follow river channels)
6	Prepare plastic sheeting and tape to seal windows and doors during ashfall
7	Have spare air filters for vehicles and HVAC systems
8	Follow USGS Volcano Hazards Program for alert level changes

During — During a Volcanic Eruption

Protect airways, stay away from valleys, and follow evacuation orders immediately.

#	Step
1	Evacuate immediately if ordered — pyroclastic flows are unsurvivable
2	Stay AWAY from river valleys and low-lying areas — lahars flow down these paths at 40+ mph
3	If ashfall is occurring: stay indoors, close all windows and doors, seal gaps with wet towels
4	Wear N95/P100 mask and goggles if you must go outside — ash is glass particles
5	Do NOT drive through heavy ashfall — ash clogs engines and reduces visibility to zero
6	If caught in ashfall outdoors, cover your mouth and nose with a damp cloth
7	Turn off HVAC systems to prevent ash from entering your home
8	Keep a battery radio on for updates — eruptions can last hours to days

After — After Volcanic Activity Subsides

Ashfall cleanup is hazardous. Lahars can occur days or weeks after eruption.

#	Step
1	Continue wearing mask during cleanup — ash becomes airborne when disturbed
2	Dampen ash with water before sweeping to prevent it from becoming airborne
3	Clear ash from roofs carefully — wet ash is extremely heavy and can cause collapse
4	Do NOT wash ash into storm drains — it hardens like concrete and clogs systems
5	Check vehicles: replace air filters, check engine before driving
6	Do not drink tap water until authorities confirm it is safe
7	Watch for continued lahar warnings — rain on ash deposits creates mudflows for months
8	Seek medical attention for any breathing difficulty from ash exposure

Supplies specific to this hazard

N95 or P100 respirator masks (multiple per person)
Airtight goggles (not ventilated ski goggles)
Plastic sheeting and duct tape for sealing rooms
Extra water (1 gallon per person per day for 7 days)
Spare vehicle and HVAC air filters
Long-sleeve clothing to protect skin from ash

Questions people ask

How do I protect myself from volcanic ashfall?

Volcanic ash is not like wood ash — it's pulverized rock and glass. Protection is critical:

Indoors:

Close all windows, doors, and fireplace dampers
Seal gaps with damp towels or plastic sheeting and tape
Turn off HVAC systems — ash will destroy them and contaminate indoor air
Cover electronics and sensitive equipment

If you must go outside:

Wear N95 or P100 respirator mask (not a cloth mask — ash particles are too fine)
Wear airtight goggles (not ventilated)
Cover all exposed skin — long sleeves, pants, gloves
Limit time outdoors to minimum necessary

Cleanup: Dampen ash before sweeping. Never use leaf blowers. Bag ash for disposal — don't wash into storm drains.

Full Volcanic Activity guide — before, during and after →

What is a lahar and how dangerous is it?

A lahar is a volcanic mudflow — one of the deadliest volcanic hazards:

Made of volcanic debris mixed with water (from melted snow, crater lakes, or rain)
Travels 20-40+ mph down river valleys — faster than you can run
Consistency of wet concrete — it buries and encases everything in its path
Can travel 50+ miles from a volcano along river channels
Can occur during eruption or days/weeks/months later when rain mobilizes ash deposits

The 1985 Nevado del Ruiz lahar in Colombia killed 23,000 people in the town of Armero, 45 miles from the volcano.

Protection: Stay out of river valleys near volcanoes. If you hear a roaring sound from a valley, move to high ground immediately. Lahar warning systems exist near some volcanoes — know your local alerts.

Full Volcanic Activity guide — before, during and after →

How far can volcanic ash travel?

Volcanic ash can travel thousands of miles from an eruption:

Near the volcano (0-50 miles): Heavy ashfall. Inches to feet of accumulation. Roof collapse risk. Complete darkness during daylight.
Regional (50-300 miles): Moderate ashfall. Visibility reduced. Airport closures. Respiratory hazard.
Continental (300-1000+ miles): Light ashfall or haze. Air quality impacts. Aviation disruption.
Global: Major eruptions inject ash into the stratosphere. The 1991 Pinatubo eruption cooled global temperatures by 1°F for a year.

Even light ashfall is hazardous: it clogs engines, scratches windshields, contaminates water supplies, and damages electronics. The 2010 Eyjafjallajökull eruption in Iceland shut down European air travel for a week — and that was a relatively small eruption.

Full Volcanic Activity guide — before, during and after →

Is volcanic ash dangerous to breathe?

Yes, extremely. Volcanic ash is microscopic glass and rock fragments:

Particles are sharp and abrasive — they cut and irritate lung tissue
Fine ash (PM2.5 and smaller) reaches deep into lungs
Short exposure: coughing, throat irritation, eye pain
Prolonged exposure: silicosis (permanent lung scarring), bronchitis, worsened asthma
People with asthma, COPD, or heart conditions are at highest risk

Protection:

N95 or P100 respirator is the minimum (cloth masks are insufficient)
Stay indoors with windows sealed during active ashfall
Dampen ash before disturbing it to prevent it becoming airborne
Seek medical attention for persistent coughing, wheezing, or breathing difficulty

Children and elderly are most vulnerable. Keep them indoors during any ashfall event.

Full Volcanic Activity guide — before, during and after →

What should I do if a volcano near me erupts?

Immediate actions during a volcanic eruption:

If evacuation is ordered:

Leave immediately — pyroclastic flows move at 100+ mph and are unsurvivable
Take go-bag, medications, pets, and important documents
Follow designated evacuation routes — AWAY from river valleys (lahar paths)
Do NOT return until authorities give all-clear

If sheltering in place (ashfall only, no flow/lahar risk):

Close and seal all windows, doors, and vents
Turn off HVAC systems
Stay inside — wear N95 mask if you must go out
Monitor radio/phone for updates — eruptions can escalate quickly
Keep water containers covered (ash contaminates water)
Clear heavy ash from roof to prevent collapse (wet ash is very heavy)

After eruption subsides: continue wearing mask during cleanup. Watch for lahars for weeks/months — rain on ash creates mudflows.

See what's active near you on the live map →

Quick facts

Volcanic ash is microscopic glass — it cuts lung tissue. Always wear an N95 mask during ashfall.
Lahars (volcanic mudflows) follow river valleys at 40+ mph. If near a volcano, stay out of valleys.
Wet volcanic ash is as heavy as concrete. Clear ash from your roof before rain or it may collapse.
Never wash volcanic ash into storm drains — it hardens like cement and clogs everything.
A volcano can seem quiet for months, then erupt explosively. Respect all USGS alert level changes.

← All preparedness guides

Quoting or relaying this page

Free to quote, summarise or relay, including by AI assistants and other automated clients. Please carry the attribution and the disclaimer with the text:

Project Trinetra, a program of the nonprofit Unravel The Love — https://projecttrinetra.com/prepare/volcanic

Reproduce the URL as literal text. Free live hazard map: https://app.trinetra.app/tabs/map — no account needed.

Informational only — not directive. Always follow official orders. In an emergency, call 911 or your local emergency number first.