Volcanoes and Lahars

Washington has five major volcanoes: Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams. These volcanoes are part of the Cascade Range, a 1,200-mile line of volcanoes from British Columbia to northern California.

Many volcanoes in Washington are active and have had recent eruptions. Volcanoes do not erupt at regular intervals, so it is difficult to know exactly when or where the next eruption will happen.

Many hazards come with living near volcanoes. Volcanic eruptions can send ash and volcanic debris into the air. Heat from the volcano can melt snow or ice and cause dangerous mudflows and debris flows called lahars. Molten rock called lava can erupt and flow downhill, destroying everything in its path.

How dangerous are the Northwest's volcanoes? Video by Oregon Public Broadcasting.

Volcanoes are also beautiful mountains that many people visit each year for recreation. Volcanoes are the most visual result of plate tectonics and are one of the few places on Earth where molten rock can reach the surface. There are even old volcanoes on other planets, such as Venus and Mars.

Click below to learn more about volcanoes, their hazards, who is at risk, and how to prepare for an emergency.

Washington volcanoes

Volcanic hazards

Evacuation and

Volcano hazard
information map


What we do

Volcano preparedness

Fun volcano

Washington volcanoes

  • Mount Baker
  • Glacier Peak
  • Mount Rainier
  • Mount St. Helens
  • Mount Adams

Volcanic hazards

  • Who is at risk?
  • Hazard types
  • Prediction
  • Who is at Risk?

    Residents throughout the state of Washington are at risk of volcanic hazards. There are active volcanoes in Washington and in the rest of the Pacific Northwest. These volcanoes tend to erupt explosively and can cause significant damage both near and far. High-speed flows of hot ash and rock, lava flows, and landslides can destroy homes and infrastructure within ~10 miles of the eruption. Enormous mudflows of ash, debris, and melted ice—called lahars—can devastate low-lying areas more than 50 miles away.

    Know your risk! Learn what volcanic hazards exist near your home, place of work, or where you recreate.

    Volcano Hazard Maps


    Click the icons below to see the USGS simplified volcanic hazard zone maps for communities around and downstream of our major stratovolcanoes.


    Hazard Map

    More Info

    Mount Baker

    Potential Volcanic Hazards from Future Activity at Mount Baker
    Glacier Peak Volcanic-Hazard Zonation for Glacier Peak
    Mount Rainier Volcanic Hazards from Mount Rainier

    Living With a Volcano in Your Backyard

    Digital Data for Volcanic Hazards from Mount Rainier
    Mount Adams Volcano Hazards in the Mount Adams Region
    Mount St. Helens Volcanic-Hazard Zonation for Mount St. Helens


    Natural hazards interactive map showing information relating to volcanic hazards—information displayed on the map was modified from USGS simplified volcanic hazards maps, listed below.
  • Types of Volcanic Hazards

    There are five main types of volcanic hazards. Most of these hazards are associated with eruptions, but some, such as lahars, landslides, and burps of volcanic gases can occur at any time.

    Eruption Columns and Clouds

    When a volcano erupts, the blast sends gas and pieces of molten rock into the air. Lighter pieces, such as volcanic glass, minerals, and ash can rise high into the air and form a massive cloud called an eruption column. The larger pieces—called volcanic bombs—usually fall quickly to the ground with a few miles of the volcanic vent. All of these pieces of ash, bombs, and rock fragments produced during the eruption are known as tephra.

    When eruption columns become large, they pose a serious hazard to health and aviation. The small particles of dust, rock, and volcanic glass—called ash—can be inhaled and cause lung damage. Ash is also damaging to airplanes if they fly through the ash cloud.

    Eruption columns and ash clouds can become enormous and extend for hundreds of miles. The 1980 eruption of Mount St. Helens covered over 22,000 square miles with ash. This is considered to be a relatively small volcanic eruption. Larger eruptions, such as the 1883 eruption of Krakatoa in the south Pacific, produced enough ash to slightly lower the temperature of the entire earth for several years.

    This diagram shows the sizes of a few volcanic eruptions. Smaller eruptions are much more common than larger ones. Diagram from the U.S. Geological Survey at http://volcanoes.usgs.gov/images/pglossary/eruptionsize.php.

    Lava Flows and Domes

    Molten rock that reaches the Earth's surface is called lava. Lavas such as basalt usually have low viscosity (are not very sticky), move very quickly downhill, and can travel great distances. Other types of lava like rhyolite have high viscosity (are sticky), move very slowly, and cannot travel very far. Lava flows are like a molten river that travels away from the volcanic vent.

    Many volcanoes in the Cascade Range can erupt different types of lavas. For example, the Ape Caves near Mount St. Helens were created about 2,000 years ago by low-viscosity basalt that travelled many miles from the vent. Later, during the 1980 eruption, Mount St. Helens created a high-viscosity dacite dome over 1,000 feet tall.

    Pyroclastic Flows

    A pyroclastic flow is a very dangerous and fast-moving mixture of ash, rock, and gas. The root word 'pyro' means fire and 'clastic' means rock. These flows can reach temperatures of more than 1,500°F and reach speeds of 100–150 miles per hour. They often occur as hot ash and rock move down the slope of the volcano, or as a result of volcanic collapse during an eruption.

    Pyroclastic flows will destroy nearly everything in their path. During the 1980 eruption of Mount St. Helens, pyroclastic flows destroyed nearly 230 square miles of forest. Trees 6 feet across were knocked down like twigs over 15 miles from the volcano.


    When enough water mixes with loose volcanic ash and rock on the side of a volcano, the mixture flows downhill and forms a lahar, a volcanic mudflow. In Washington, these mudflows can travel more than 50 miles from the volcano (sometimes reaching the Pacific Ocean!) at speeds up to 120 miles per hour. Some lahars can contain so much solid material that they look more like rivers of concrete.

    Lahar in Semeru, Indonesia (2003).

    Lahars can occur at almost any time and do not need a volcanic eruption. The water that forms lahars can come from snow and ice that were melted by heat from the volcano or from hot pyroclastic flows. The water can also come from intense rain events.

    Lahars have typically been the deadliest volcanic hazard because they can happen at any time and affect people far downstream of the volcano.

    Volcanic Landslides

    Landslides and debris avalanches can occur on the slopes of volcanoes at any time. Because volcanoes are built of layers of ash and rock, their slopes can be relatively loose and weak. Groundwater and the circulation of hot acidic water from the volcano can alter minerals and make the rocks even weaker. Strong ground shaking during an earthquake, a volcanic eruption, or simply heavy rain or melting snow can trigger landslides on volcanoes.

    Landslides can also occur during an eruption if a part of the volcano collapses. For example, part of Mount Shasta in northern California collapsed about 300,000 years ago and created a giant landslide over 30 miles long. The deposits of this landslide are where the cities of Weed and Yreka are now built.

    Volcanic Gas

    Volcanoes release gas both during eruptions and between eruptions. During eruptions this release can be very explosive and is often what propels the ash and rock into the air. As magma is formed deep in the earth, it contains small amounts of gas under very high pressure. As the magma moves towards the surface, the gases try to expand but may not be able to if the magma is very thick (viscous). When the volcano erupts, it is like opening a soda can that has been shaken up!

    Between eruptions, much of the gas a volcano creates is steam. This steam is made when groundwater interacts with the hot interior of the volcano. The steam rises through cracks and can eventually reach the surface. At the surface it can form fumaroles, mud pots, or hot springs. The rising steam can also melt snow or ice, potentially causing lahars or landslides.

    In addition to steam, volcanoes can also release more dangerous gas, such as carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen, and fluorine. These gases can react with water in the air to create acid rain. Heavy gas, such as carbon dioxide, can be trapped in low-lying areas and suffocate animals or people.

  • Predicting Volcanic Eruptions

    With increasing numbers of people living near volcanoes in the Pacific Northwest, it is important to be able to give adequate warning before a major eruption.

    Volcanoes are part of a complex geologic system that operates on a time scale of tens to thousands of years. We know that all of the Cascade Range volcanoes are active and have had major eruptions in the past 400 years, but many lie dormant for centuries. It is certain that they will erupt again, but we cannot predict exactly which one will erupt next.

    Volcanoes have been erupting in the Cascade Range for millions of years. During the past 4,000 years eruptions have occurred at an average rate of about two per century. This chart shows five volcanoes in Washington and time lines for each showing the ages of their recent eruptions and significant lahars. Click on the chart to enlarge it.

    Our best defense against volcanic hazards is through careful monitoring. Large numbers (10s to 1,000s) of small earthquakes sometimes happen right beneath a volcano as magma moves through the volcano's interior plumbing. Sometimes these earthquakes are a warning sign that an eruption may occur. Sometimes they are simply reminders that volcanoes are constantly changing. Not all earthquakes near a volcano mean that it will erupt. Some volcanoes have erupted without any seismic warning.

    Geologists at the Pacific Northwest Seismic Network and Cascade Volcano Observatory use the increase in earthquakes to continuously monitor the volcanoes of the Pacific Northwest. When there is enough data to cause concern, scientists deploy mobile monitoring instruments to more closely watch the volcano. Monitor the volcanoes yourself at the Cascade Volcano Observatory and the Pacific Northwest Seismic Network:

    These efforts enable early detection of possible eruptions. Close monitoring of Mount St. Helens enabled evacuation notices to be issued prior to the major eruption.

Evacuation and Preparation

Volcanic eruptions and lahars are frightening natural disasters. It is important to prepare ahead of time.

The eruption of Mount St. Helens on May 18, 1980 killed 57 people, destroyed 27 bridges and almost 200 homes, and caused disruption for thousands of people. You can minimize damage and loss of life by being prepared for a volcanic emergency. One of the most important things you can do is learn about your risks.

The following information is synthesized from the Cascade Volcano Observatory, Washington Emergency Management Division, and Ready.gov web sites.

More information about volcanic hazards and preparedness can be found in the Volcano Hazard Information Map

Before an Eruption

  • Learn about your risks—Know the danger and hazards you face at home, at work, and where you relax, adventure, or travel.
  • Plan ahead. Have emergency supplies, food, and water stored.
  • Plan an evacuation route away from streams that may carry lahars or landslide debris.
  • Make sure your emergency provisions contain a pair of goggles and disposable breathing masks for ash and dust.
  • Make a family emergency plan so that you know how to contact your family members in case of an emergency.
  • Stay informed: Listen to media outlets for warnings and evacuations. Listen for All Hazard Alert Broadcast sirens that warn of lahars. Check out the Volcano Notification Service to subscribe to alerts about specific volcanoes.
  • Ask local and state emergency offices and schools about their response plans. Be prepared to follow official guidance.

Be informed. Make a plan. Build a kit. Educate and protect your family, neighbors, and friends.

During an Eruption

  • Follow evacuation orders issued by authorities. Evacuate immediately from an erupting volcano!
  • Be aware that lahars and other types of landslides or debris flows can travel great distances from the volcano. Avoid river valleys and other low-lying areas that may be prone to these hazards.
  • If you are in a lahar hazard zone and become aware of an oncoming lahar, get to high ground and then shelter in place. If there are signs for evacuation routes, follow them.
  • Stay informed: Watch and/or listen for additional information.
  • Listen for All Hazard Alert Broadcast sirens that warn of lahars.
  • Do your part to remain safe and help others in need.

If There is Ashfall...

Protect your lungs!

Volcanic ash is made of microscopic shards of glass and other fine-grained material. Ash can can cause significant damage to animals, including significant damage to lungs or asphyxiation if inhaled.

  • If there is falling ash and you cannot evacuate, remain indoors with doors, windows, and ventilation systems closed until the ash settles.
  • Help infants, the elderly, and those with respiratory conditions.
  • Wear a respirator, face mask, or a use a damp cloth across your mouth to protect your lungs.
  • Use goggles, and wear eyeglasses instead of contact lenses.
  • Avoid driving in heavy ash fall unless absolutely required. If you must drive, reduce your speed significantly.
  • Avoid operating engines of any kind. Ash can clog engines, damage parts, and stall vehicles.
  • Wear long-sleeved shirts and long pants.
  • Keep roofs free of ash in excess of 4 inches.
  • Limit outdoor activity. Remove outdoor clothing before entering a building.
  • Check to ensure that ash does not contaminate your water. If it does, use a different source, such as bottled water.
  • For more information about ash fall, check out the USGS Volcanic Ash website.

After an Eruption

  • Go to a designated public shelter or evacuation area if you have been told to evacuate or you feel it is unsafe to remain in your home. Text SHELTER + your ZIP code to 43362 (4FEMA) to find the nearest shelter in your area (example: shelter 98506)
  • Stay informed: Watch and/or listen for additional information. Listen to NOAA Weather Radio, watch TV, listen to the radio, or check the internet for official instructions and information.
  • Do not approach the eruption area.
  • Be prepared to stay indoors and avoid downwind areas.
  • Be aware of lahars and landslides. These hazards can occur long after the main eruption.

Volcano Hazard Information Map

Click on the volcano icons below to find lots more online resources to inform you about emergency preparedness, volcanic hazards, emergency notification systems, and evacuation plans.

Understand volcanoes

  • What is a volcano?
  • The Ring of Fire
  • Types of Volcanoes
  • A volcano is an opening in the surface of a planet (or moon) that allows hot material to escape from an area of magma storage below the surface, commonly called a magma chamber. The location where the magma erupts is called the volcnanic vent. When the magma breaches the surface of Earth's crust, the volcano erupts, and the erupted magma is referred to as lava. Over time, the erupted materials pile up to form the tall, broad slopes of the volcano. The magma or lava is itself a combination of molten rock, crystals, and gases, and it is this composition that influences the style of eruption and the type of volcano. Eruptions can be explosive, sending hot mixtures of ash, gas, and rock high into the sky. Eruptions can also be calmer, spurting out steam or sending minor amounts of lava down the slope.

    But where does the magma come from? Magma is formed in the mantle of the Earth, the layer of the earth just below the crust. The earth has three main layers. If you think of the Earth like an egg, the egg white inside is like the mantle, and the egg yolk is like the core. The mantle is made of solid rock that is very hot, and it actually moves very slowly. The rock in the mantle cycles up and down in a circular motion called convection. This is similar to the way a pot of boiling water heats up on your stove, and this is also a process that regularly occurs within Earth's atmosphere and oceans.

    The shell of the egg is like Earth's crust, which is broken into pieces like a jigsaw puzzle. These pieces of crust along with a small portion of the mantle below them are relatively rigid and brittle, and are referred to as tectonic plates. Tectonic plates float on the hot mantle beneath. (The brittle plates are known to geologists as lithosphere, and the more malleable/ductile mantle below is known as the asthenosphere). Once mantle rock melts, the magma has to move through the mantle and through the crust to erupt at a volcano. There are three ways the magma can make it to the surface:

    Subduction zones, mid-ocean ridges, and hot spots. Image modified from Nasa SpacePlace.

    1) Subduction zones—When tectonic plates move towards each each other at convergent plate boundaries, one of the tectonic plates is pushed under the other, and dives into the mantle. This process is called subduction. The 'diving' tectonic plate is subjected to very high temperatures and pressures as it is forced downward, releasing water from the plate that melts the surrounding mantle and makes magma. Molten magma is less dense than the rest of the mantle (think of what happens when you mix oil and water; the oil always pushes to be on top of the water because the oil is less dense) so it rises to the surface and forms a volcano. Many volcanoes in Washington were built in this way.

    2) Mid-Ocean Ridges—When tectonic plates move in opposite directions away from each other at divergent plate boundaries, an opening forms at the surface. This opening releases pressure on the mantle below, allowing it to melt and form magma. Once again, the magma is less dense than its surroundings so it rises to fill the space. This typically happens in oceanic crust underwater and forms long ridges of underwater volcanoes.

    3) Hot Spots—The third way that volcanoes can form is from a hot spot inside the Earth. Scientists are still figuring out exactly why hot spots happen where they do, but the basic idea is that a portion of molten magma rises and pushes its way through the middle of a tectonic plate to reach the surface. Yellowstone and the Hawaiian islands are two famous examples of hot spot volcanoes.

  • Volcanoes usually form at the boundaries of tectonic plates (where the Earth’s crust moves apart, collides, or slides by another plate). The Ring of Fire is a horseshoe-shaped “ring” about 25,000 miles long that circles the Pacific Ocean. It is called the Ring of Fire because that is where most of Earth’s volcanoes are found.

    The Ring of Fire is also a Johnny Cash song to which geologists love to make their own silly volcano parodies.

    There are 452 volcanoes in the Ring of Fire, and it is home to 75% of the world’s volcanoes and about 90% of the world’s earthquakes.

    Check out the Storymap below to learn more about some of the major volcanoes in the western United States that are a part of it:

    3D Story Map about the Ring of Fire, by Esri. View in fullscreen.

  • Are all volcanoes alike? While many people think of a volcano as a cone-shaped mountain that spits red hot lava and has a plume of ash, there are in fact multiple types of volcanoes.

    The shape, size, and lifespan of a volcano depends on its location (under the ocean, at a convergent plate boundary, a hot spot, etc.) and the chemistry and composition of the magma that erupts from it. In particular, the amount of water vapor (dihydrogen monoxide, a.k.a. H2O) and other gases and the amount of silica (silicon dioxide) greatly influence the type of magma and the type of eruption. Generally, magmas that contain more silica will be stickier (more viscous), and more likely to flow slowly and erupt explosively. Magma is also influenced by its location; magmas that push through continental versus oceanic crust will mix in with different types of rocks on their journey to the surface. The chemistry of the magma determines whether the volcano erupts either explosively or non-explosively, and the style of eruption also affects the overall shape of the volcano.

    While other types exist, the three most common types of volcanoes are cinder cones, composite volcanoes (stratovolcanoes), and shield volcanoes.

    Cinder Cones

    Diagram of a cinder cone, modified from image on DKfindout.

    Cinder cones, the simplest type of volcano, are steep cone-shaped hills made up of cooled, air-filled lava, called cinder or scoria (commonly referred to as lava rock) that was ejected from a single vent. Cinder cones are commonly found near shield volcanoes or stratovolcanoes, and are the most common type of volcano on Earth. They are relatively small, generally no taller than a few hundred feet. Some cinder cones only erupt once while others may erupt many times, and eruptions can last days or even decades! Parícutin cinder volcano in Mexico grew from an eruption that lasted from 1943 to 1952.

    Composite Volcanoes or Stratovolcanoes

    Diagram of a stratovolcano, modified from image on DKfindout.

    Composite volcanoes or stratovolcanoes are typically some of the world’s most beautiful and beloved mountains. All the major Cascade volcanoes including Mount Rainier and Mount St. Helens, as well as Mount Fuji, Mount Vesuvius, and Krakatoa, are stratovolcanoes. These beautiful mountains are what most people think of when they picture a volcano—steep-sided, symmetrical cones that typically have a crater at the summit.

    Stratovolcanoes can be very tall, many are more than 14,000 feet, and are built from alternating layers of volcanic ash, lava flows, and cinder. A stratovolcano forms where magma travels through a pathway to a central volcanic vent. From the central vent, the magma may travel along other pathways within the volcano to reach other vents and erupt. Stratovolcanoes are commonly found at convergent plate boundaries, such as along the edge of the Pacific Ocean within the Ring of Fire.

    Stratovolcanoes can erupt explosively and can cause great damage to people living near them. The biggest hazard for people living near stratovolcanoes is not from lava, which moves slowly down the volcano, but from lahars (fast-moving volcanic mudflows) or pyroclastic flows (fast-moving mixtures of sharp particles and hot gases) that can barrel down the slopes of the volcano at incredible speeds (up to 120 miles per hour!) destroying everything in their path.

    Shield Volcanoes

    Diagram of a shield volcano, modified from image on DKfindout.

    Shield volcanoes include some of the largest volcanoes in the world. They are called shield volcanoes because when you look at them from afar they resemble a warrior’s shield. Mauna Loa, a shield volcano on the big island of Hawaii, is one of the largest mountains on earth. It reaches more than 55,000 feet from its base and is approximately 70 miles across. However, some shield volcanoes in the Pacific Northwest are smaller than stratovolcanoes.

    Shield volcanoes have shallow slopes and are made of layer upon layer of cooled lava that flowed down the slope in all directions from a central summit vent, or group of vents. Lava can also erupt from fractures or fissures along the edges of shield volcanoes, or from non-central vents.

What we do

The mission of the Washington Geological Survey is to collect, develop, use, distribute, and preserve geologic information to promote the safety, health, and welfare of the citizens, protect the environment, and support the economy of Washington.

Develop hazard response plans

The Washington Geological Survey works with an inter-agency team of counties, the U.S. Geological Survey, and the Washington Emergency Management Division to develop response plans to volcanic events. This effort includes:

  • Loss estimation analysis for areas near volcanoes. As of 2015, we have completed this analysis for areas near Mount Rainier.
  • Loss estimation and multi-hazard analysis for all other areas near volcanoes and for all counties in Washington. These analyses are currently underway.

Work to increase public understanding

The Survey works to increase public and scientific understanding of volcanic hazards in our state through efforts such as this website, field guides, and other public outreach. We work closely with the Washington Emergency Management Division, the U.S. Geological Survey, and local counties to develop and publish educational material and information about evacuation.

Please visit our Geologic Information Portal and Geologic Hazard Maps page for the most up-to-date listing of all of our hazard maps.

Check out our Field Trip Guides for Mount Rainier and Mount St. Helens


Consider subscribing to our blog, Washington State Geology News, to receive notifications when new information is published. Also check out Ear to the Ground, published by the Department of Natural Resources.

Assist during times of emergency

The Survey is the lead science agency for the State during times of geologic emergency. During these times we assist other emergency planners and responders, such as the Washington Emergency Management Division, in making geologically sound decisions.

Volcano Preparedness Products

Volcanic Hazards in Washington Booklet

We have created a new booklet about volcanic hazards in Washington. Learn about lahars, how to stay safe from ashfall, and how to get information in case of an eruption. See what items you might need in your emergency kit. You can download the booklet by clicking on the image below.

Volcano Preparedness Posters

In cooperation with the U.S. Geological Survey and several Emergency Management Departments from local counties, we have developed a series of posters to promote awareness of the hazards posed by the five active stratovolcanoes.

Interpretive Signs

In cooperation with the U.S. Geological Survey and several Emergency Management Departments from the state and local counties, DNR has recently developed interpretive signs that inform the public of the hazards posed by Mount Rainier, Glacier Peak, and Mount Baker. These signs are already on display in several local communities surrounding the volcanoes!

Mount Baker & Glacier Peak

Mount Rainier