Types of Volcanoes

Are all volcanoes alike? While many people think of a volcano as cone-shaped mountain that spits red hot lava and has a plume of ash like the one shown below, in fact, there are 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.), the chemistry of the magma that erupts from it, and the amount of ash and lava in the eruption. Depending on the chemistry of the magma, the volcano can erupt either explosively or non-explosively; the style of eruption also affects the overall shape of the volcano.

While other types exist, there are three main types of volcanoes. They are cinder cones, composite volcanoes (stratovolcanoes), and shield volcanoes.



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 were ejected from a single vent. Cinder cones are commonly found near shield volcanoes or stratovolcanoes. Some only erupt once such as the famous Paricutin cinder cone, while others may erupt many times.


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 from conduits where magma travels from deep within the Earth to the surface through a central vent which connects to multiple radiating dikes and secondary vents. 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 (see video below) 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) that can barrel down the slopes of the volcano at incredible speeds (up to 120 miles per hour!) destroying everything in their path.


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

Shield volcanoes are 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 Hawaii’s big island is the largest single mountain on earth. It reaches 30,000 feet above the ocean floor and is approximately 100 miles across at its base.

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.


What is a Volcano?

ger_hazards_volc_understanding_volcanoesA volcano is an opening in the surface of a planet (or moon) that allows hot material to escape from the magma chamber below the surface. When the hot material, such as lava, ash, and gas make their way to the surface, the volcano erupts. The style of eruption depends on the type of magma. Eruptions can be explosive, sending hot mixtures of ash and gas high into the sky; or they can be calm, only sending small amounts of lava down the slope.

Several factors determine the explosiveness of a volcanic eruption. These include: dissolved gases, water vapor, temperature, and composition. The composition determines the viscosity, or the resistance to flow, of the magma. Magmas with a high viscosity are thick and slow moving, and have a high silica content. Low viscosity magmas are thin and runny, and have a low silica content.

The three types of magma are:



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 When tectonic plates bump into each other (converge) one of the tectonic plates can be pushed under another one deep into the Earth under the crust (called subduction). The tectonic plate that was forced into the Earth then melts from the high temperature and high pressure and can eventually rise to the surface as magma and form a volcano from the melted crust. The big volcanoes in Washington are formed this way.

2) Mid-Ocean Ridges When tectonic plates move away from each other (diverge) the hot, buoyant magma beneath the crust rises to fill the space. This typically happens in oceanic crust underwater and forms “black smokers”.

3) Hot Spots The third way that volcanoes can form is at 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 magma rises and pushes its way to the surface through the tectonic plate. Yellowstone and the Hawaiian islands are two famous examples of hot spot volcanoes.


May is Volcano Preparedness Month

3345May is Volcano Preparedness Month, and to prepare we will bring you a different volcano profile each week and provide information on how to prepare for any emergency. Preparing today could save you and your family during the next eruptive event.ger_hazards_volc_hazard_overview_1140.png

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 long line of volcanoes that stretches from British Columbia to northern California. Each of Washington’s five major stratovolcanoes are still active. In fact, all of them except for Mount Adams have erupted in the last 250 years. Volcanoes do not erupt at regular intervals, so it is difficult to know exactly when or where the next eruption will happen. It is important to prepare ahead of time.

Learn about the volcanic hazards where you live, work, and play; make a family emergency plan today!



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.



  • Learn about your risks—Know the danger and hazards you face at home, at work, and where you recreate 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.


    • 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 signed 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.


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.


    • 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.


Stay tuned for: Volcano Hazards portal update, Volcano webpage updates, and more!

New Webpage Available: Rockhounding


Washington has an extraordinary variety of rocks and fossils. Collectors have the opportunity to find beautiful agate, amethyst, garnet, jasper, opal, and even the occasional nugget of gold. Our state also has a plethora of fossils including crinoids, clams, trilobites, snails, corals, and at least one dinosaur. The state also has abundant petrified wood, which is the Washington State Gem, and has had over 40 Columbian Mammoth discoveries, which is the Washington State Fossil.

Check out our rockhounding page to find out:

Minerals and Fossils in Washington

rockhounding_storymap.jpgOur Mineral and Fossil Story Map compiles known locations of minerals and fossils such as petrified and opalized wood, fossil crabs, cephalopods, gastropods, trilobites, pelecypods, braciopods, leaf fossils, gemstones, geodes, zeolites, and chalcedony and opal. It is best viewed in full-screen mode.

The Rules

Be aware that this map may show locations where the minerals are amazing, but where rockhounding is not permissible. Determining land ownership and collection rules at that site is your first responsibility.

Before you set out, determine land ownership of your area of interest, learn the permissible collection activities and that owner’s rules governing where you can collect, what you can and cannot collect, and how it may legally be collected.

The consequences for collecting materials without permission are steep, as in most cases this would be considered trespassing and stealing.

ger_rockhounding_adit.pngSafety First

You’re responsible for your own safety. Steer clear of open mine tunnels or shafts—they can collapse, crushing you or trapping you inside. No mineral specimen is worth your life.

Where To Start

Our “Where Do I Start?” tab provides links to:

  • Museums like the Burke Museum in Seattle or Stonerose Interpretive Center in Eastern Washington
  • Local rock and gem clubs
  • Handbooks and publications on gold
  • Other rockhounding websites
  • And many others





April TsuInfo Now Available


This issue of TsuInfo includes articles on:

  • Upcoming Cascadia Rising exercise in the Pacific Northwest
  • The March CARIBE WAVE 2016 tsunami exercise
  • Tsunami Preparedness Week Activities in California during March 20-26, 2016

Find this month’s issue here: http://file.dnr.wa.gov/publications/ger_tsuinfo_2016_v18_no2.pdf

Stay tuned for more info on Cascadia Rising in June!

TSUINFO ALERT IS A BI-MONTHLY newsletter that links scientists, emergency responders, government officials, and community planners to the latest tsunami news and research. This newsletter is published by the Washington Department of Natural Resources, Division of Geology and Earth Resources on behalf of the National Tsunami Hazard Mitigation Program, a state/federal partnership funded through the National Oceanic and Atmospheric Administration. It is made possible by a grant from the Federal Emergency Management Agency via the Washington Military Department, Division of Emergency Management.





Earth Day 2016: Moving Toward Green Energy

What is Geothermal Energy?


Schematic representation of an ideal geothermal system

Geothermal energy is thermal energy generated and stored in the earth. When most people think of geothermal they think of hot springs, fumaroles, and geysers. These are surface features that are linked (through faults and fractures) to the subsurface hydrothermal reservoir. Geothermal energy can be harnessed by drilling into hydrothermal reservoirs and extracting the hot fluids and/or steam.

Check out this Geothermal 101 video or this one on geothermal heat pumps to learn more.

Geologists and engineers can tap deep into a hydrothermal reservoirs to generate electricity, or use the shallow heat beneath the surface to heat and cool homes through geothermal heat pumps.

How is it used?


Geothermal power plant, USGS photo

Geothermal energy is a renewable, environmentally friendly, baseload power source that has potential to be successful in Washington State.  It has many uses, which are dependent upon the temperature of the resource. Low (<194 degrees F) and moderate temperature (194–302 degrees F) geothermal resources can be used for residential and commercial heating/cooling, or for agriculture. Moderate to high-temperature (>302 degrees F) resources can be used to generate electricity. For more information, see the USGS Fact Sheet.

Geothermal Potential of Washington

Washington is home to five major active volcanoes and numerous hot springs and fumaroles (check out DGER’s geothermal portal to see where they are all located).


Most of the high-temperature wells and hot springs in Washington are associated with active volcanism and recent faulting. Faults provide pathways for heated fluids to travel from their source to the surface. There is also a large, yet poorly understood area of warm water in the Columbia Basin in eastern Washington.


2014 geothermal resource assessment results

We conducted a statewide geothermal resource assessment in 2014  which revealed three areas in the Cascade Range with elevated geothermal potential within developable land: the Mount St. Helens seismic zone, Mount Baker, and the Wind River valley (outlined in the map above). These three sites are currently being studied in detail by DGER, Seattle based geothermal company AltaRock Energy Inc., USGS, and a number of other talented partners. This study is funded by the U.S. Department of Energy Geothermal Technologies Office and is in the second phase of exploration now.

Please check back soon for project updates from this year’s field season.


The Great M7.8 San Francisco Earthquake, April 18, 1906

110 years later, why the San Francisco Earthquake still matters


Wreckage of buildings from the M7.8 San Francisco earthquake. (from University of Nebraska at Lincoln Gallery of the Open Frontier)

The San Francisco Earthquake of 1906 was one of the most important geologic events of our time. Shaking damage destroyed many buildings, but it was the fires caused by severed gas lines during the earthquake that caused the city to burn for days after the shaking had stopped. More than 3,000 people are estimated to have died as a result, as well as 225,000 survivors left homeless by the 28,000 buildings that were destroyed. Check out the photo collections in these archives.

The earthquake itself was significant at an M7.8, but the damage it caused put into motion more intense focus on the study of earthquakes. This disaster spurred a movement for more scientific study of the geology and fault systems in California and eventually other locations along the coast. Read more about the “Dawn of Scientific Revolution” from the USGS.

How we are preparing for the next “big one”


Earthquake early warning systems like ShakeAlert work because the warning message can be transmitted almost instantaneously, whereas the shaking waves from the earthquake travel through the shallow layer of the Earth at speeds of one to a few kilometers per second (0.5-3 miles per second). This diagram shows how such a system would operate. When an earthquake occurs, both compressional (P) waves and transverse (S) waves radiate outward from the epicenter. The P wave, which travels fastest, trips sensors placed in the landscape, causing alert signals to be sent ahead, giving people and automated electronic systems some time (seconds to minutes) to take precautionary actions before damage can begin with the arrival of the slower, bur stronger S waves and later-arriving surface waves. Computers and mobile phones receiving the alert message calculate the expected arrival time and intensity of shaking at your location. USGS image created by Erin Burkett (USGS) and Jeff Goertzen (Orange County Register).

To try and mitigate damage and loss of  life, a coalition of scientists are working toward implementing an early warning system in California, Oregon, and Washington. Earthquake early warning (EEW) systems can measure earthquakes fast enough to transmit an alarm to cell phones and other reception sites to give valuable seconds of warning to prepare for the disaster.

According to the USGS Earthquake Hazards Program, a few seconds could give us enough time to:

  • Public: Citizens, including schoolchildren, drop, cover, and hold on; turn off stoves, safely stop vehicles.
  • Businesses: Personnel move to safe locations, automated systems ensure elevators doors are open, production lines are shut down, sensitive equipment is placed in a safe mode.
  • Medical services: Surgeons, dentists, and others stop delicate procedures.
  • Emergency responders: Open firehouse doors, personnel prepare and prioritize response decisions.
  • Power infrastructure: Protect power stations and grid facilities from strong shaking.

This prototype system, called ShakeAlert, will hopefully become fully functional in the coming years. Learn more about ShakeAlert, by watching a video here or reading this report.

As always, check out our Earthquakes and faults webpage to learn more about Washington’s mapped faults, and what to do before, during, and after an earthquake.

Geology Portal Update


The Geochronology and Seismogenic  Features databases have been updated and are now available on the Geology Portal. The datasets can also be downloaded direct from our GIS & Databases webpage.

Updates to the datasets include the addition of: age analysis data from several new publications,  earthquake data from the last few years, and hyperlinks to paleoseismic investigation publications (trenches).  Happy clicking!




Czajkowski, J. L., 2016, Washington State geochronology database—GIS data: Washington Division of Geology and Earth Resources Digital Data Series 6, version 1.1, originally released November, 2014. [http://www.dnr.wa.gov/publications/ger_portal_geochronology.zip]

Bowman, J. D.; Czajkowski, J. L., 2016, Washington State seismogenic features database–GIS data: Washington Division of Geology and Earth Resources Digital Data Series 1, version 4.1, originally issued December 2013. [http://www.dnr.wa.gov/publications/ger_portal_seismogenic_features.zip]

Rainforest Rivers of the Outer Olympic Coast


New LiDAR product available!

This imagery shows floodplain details from five rivers on the outer Olympic Peninsula—the Quinault, Queets, Hoh, Bogachiel/Quillayute, and Sol Duc. The headwaters of these rivers begin in melting snowfields and glaciers of the Olympic Mountains. They then flow through a region of dense temperate rainforest and westward to the Pacific Ocean.

The brightest white areas represent the river elevation (set to 0 feet), and as elevations increase in the floodplains, the white progressively changes from light green to dark green. This type of model shows where river channels have migrated in the past by vividly displaying floodplain features such as terraces, meander scars, and oxbow lakes.

Channel migration can be affected by a number of factors including topography, geology, land use, and land cover, such as forest. Large woody debris from the western Olympic Peninsula’s mature rainforest stabilizes floodplains and reduces channel migration by restricting flow and keeping sediment in place. Historic removal of large trees from riparian zones in the lower reaches of these rivers has increased sediment transport and channel movement.

This poster was made by DGER cartographer Dan Coe and is available here for download.

Check out our Presentation Archive for other cool products!



New LiDAR Collection Underway


This winter and spring have witnessed a flurry of LiDAR-(light detection and ranging) related activity at the Division of Geology and Earth Resources (DGER) as the new LiDAR program begins to take shape.  The ongoing collection of new aerial LiDAR data in western Washington will ultimately serve as the foundation data for mapping, geologic hazard mitigation, urban planning, habitat and vegetation modeling, and transportation applications.

Our first few days of sunny weather allowed LiDAR vendors to make lots of headway in the lower elevations. Flights for the project began on March 17th in both the northern and southern collection areas (see maps below). Collection flights in higher elevation areas will follow the snowline.

Collection and Partnerships

King County LiDAR Project:

DGER is an active participant in the King County LiDAR mapping project which began collections in February.  Managed by Kitsap County for the Puget Sound LiDAR Consortium, this project aims to collect more than 1,000 square miles of LiDAR data.

A couple of clear flying days have resulted in steady progress in the Puget Lowland areas.  Quantum Spatial Inc., the vendor that is contracted for both collection and data processing, reported that more than 75% of the area has been flown. Collection of the higher elevation areas will follow later this spring or summer, as snow retreats.


Current acquisition status map for the King County LiDAR project

 USGS 3D Elevation Program (3DEP):

In partnership with the Skagit, Whatcom, Snohomish, and Lewis counties, the Swinomish Tribe, Sierra Pacific Industries, and Seattle City Light, DGER was awarded a grant from the 3DEP  program this past fall.

The 3DEP program aims to:

—Systematically acquire LiDAR elevation data over the United States over the next 8 years

—Offer grants to local agencies to partner on the collection and processing costs

—Collect over 5,400 square miles of LiDAR data in two areas of interest (AOI)

  • The northern AOI will cover large areas of Whatcom, Skagit, and Snohomish counties, and
  • The southern AOI will cover portions of Thurston, Lewis, Gray’s Harbor, Wahkiakum, Cowlitz and Clark counties

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Another collection window for Puget Lowland areas will present itself again in autumn, when leaves have fallen, allowing higher accuracy for ground elevation models. We like to avoid collecting data in the summer as ‘leaf-on’ conditions reduce the density of ground hits we can obtain.

Want to know more about how LiDAR is collected?

Check out the “What is LiDAR?” tab on our  website and watch an informative video here, by NEON Education.


A laser is mounted on a light aircraft in order to collect the data

Updates on these projects and other news for the LiDAR program will be posted through this blog or on DGER’s LiDAR webpage, so stay tuned!