The Ten Most Hazardous US Volcanoes

Update, October 29, 2018: The Yellowstone Observatory posted more information on Yellowstone Caldera’s ranking and on the threat assessment process today.

Original post:
It’s a little early to be making top-ten lists for 2018, but the USGS just released their 2018 update to the National Volcanic Threat Assessment:

The link takes you to an abstract of the report and a free PDF download.

Note that threat level doesn’t mean that the volcano is about to erupt. They looked at the bigger picture, placing volcanoes according to how they scored on a list of potential hazards.

If we had assessed only the hazards aspects of U.S. volcanoes, then the generally more explosive volcanoes in Alaska and CNMI [the Marianas**] would be more strongly represented in the higher (more hazardous) ranks. Because we include exposure factors in the assessment, volcanoes in CONUS are more strongly represented in the highest threat category owing to the greater nearby ground-based and airborne population, and more critical infrastructure exposed to volcano hazards . . .Eleven of the 18 [very high threat] volcanoes are in Washington, Oregon, and California, where explosive and often snow- and ice-covered edifices can project flowage hazards long distances to reach densely populated and highly developed areas. Five of the 18 volcanoes are in Alaska, near important population centers, economic infrastructure, or below busy air traffic corridors. The remaining two very high threat volcanoes are on the Island of Hawaiʻi, where densely populated and highly developed areas now exist on the flanks of highly active volcanoes. Large eruptions from any of these very high threat volcanoes could cause regional- or national-scale disasters.

**: In its October 26th weekly update, the USGS says that Supertyphoon Yutu has destroyed ground-based monitoring equipment on Saipan, affecting all CNMI volcanoes, including Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Sarigan, Pagan, Almagan and Guguan. Only satellite monitoring is possible now.

Ten Most Hazardous Volcanoes

The ten highest-threat volcanoes on the list are:

1. Kilauea, in Hawaii. We know. We know.

2. Mount St. Helens, in Washington. Global Volcanism page (GVP). Local volcano observatory (VO) page. Wikipedia page.

3. Mount Rainier, in Washington. GVP. CVO. Wikipedia. Continue reading


Update on Popocatépetl

Volcanologists at the University of Mexico released a bulletin (Spanish) this morning; here is the Google Translate version. Click the link in the top menu for more information about Popocatépetl as well as updates.

Bulletin UNAM-DGCS-620
University City
11:00 hs. September 29, 2018

Ramón Espinasa Pereña

Ana Lillian MartĂ­n del Pozo


• Exhalations and vulcano-tectonic earthquakes have been increasing, because a significant amount of magma is rising, said Ramón Espinasa, from the Cenapred
• The Geophysics Institute placed well seismographs to monitor the activity and predict a major eruption
• Don Goyo has not gone to sleep since December 1994 and the tremor of September 19 of last year, whose epicenter was in a relatively nearby area, affected him, said Ana Lillian Martín del Pozzo, of IGf

The Popocatépetl volcano presents a lot of activity, and is increasing; An example of this is the increase in volcano-tectonic exhalations and earthquakes, the latter of an order of magnitude greater than that seen in the last 24 years.

This data indicates that a significant amount of magma is rising and “within months, a year or the day after tomorrow”, could present an even more important activity than it had, said RamĂłn Espinasa Pereña, deputy director of Volcanic Risks at the UNAM. the Research Directorate of the National Center for Disaster Prevention (Cenapred).

Continue reading

Meanwhile, in Puebla . . .

See update at bottom of post, or click the Popocatepetl link at the top of this page.

This is a 2011 view of nearby Popocatepetl volcano from downtown Puebla.

Today, people in this Mexican city are watching Popocatepetl with concern (you can follow updates on its activity through the link in the top menu–it has been a bit more restless lately).

Reportedly (Spanish), Puebla State’s Civil Protection director has made a public statement. Per Google Translate of this linked news story:

Although in the last hours and days the Popocatépetl volcano has presented constant explosive activity, with incandescent fragments expelled by the crater, the Civil Protection director of the state of Puebla, Rubén Darío Herrera Cabrera, assures that it is a normal cyclic activity and that there is nothing to worry about.

The incandescent fragments, explained the head of Civil Protection, are pieces of the dome . . .

Even though spectacular fumaroles have been seen in recent days, the largest of which is 2,400 meters above the crater, there is nothing to worry about; “Another point that is constantly monitored is the seismicity and that is totally low, we have very few reports of seismicity, which gives us peace of mind,” said Herrera Cabrera, adding that the volcanic warning light continues in Yellow Phase 2.

This is an image from last night’s explosion as seen from one of CENAPRED’s webcams:


This is a night-time image, but the camera is a very good one and the Moon is quite bright. That’s chunks of incandescent material blown out of the crater, not flowing lava. Popo’s lava is very sticky and forms a dome in its crater that eventually pressurizes and blows up–apparently this is the demise of Dome #78. (CENAPRED)

Again, just click on the link at the top of the page for links to more information about Popocatepetl and updates from me.

Update, September 25, 2018: Popo got into a dramatic mood yesterday; updates are at the Popocatepetl link at the top of this page. Meanwhile, here is an eruption the volcanologists monitoring this volcano captured–it’s just one of several yesterday:

Featured image: Luisalvaz, via Wikimedia. CC BY-SA 4.0

Guest Videos: What Is Lightning?

When thunder roars, go indoors! — words of wisdom from James Spann and other meteorologists.

Note that on Earth, lightning is most frequent in equatorial regions.

For almost 40 years–ever since Voyager passed the planet Jupiter–scientists have wondered why lightning is more frequent at Jupiter’s poles. It otherwise seems to work pretty much the same way as terrestrial lightning.

Thanks to data from the Juno mission, they may have figured it out now.

Meanwhile, back on Earth–
Continue reading

Guest Video: The Salton Sea

A study at the end of June made headlines about earthquake hazard on the San Andreas Fault. The research looked at the area covered by the Salton Sea:

According to news reports, geologists found:

. . . a nearly 15.5-mile-long, sheared zone with two, nearly parallel master faults and hundreds of smaller, rung-like cross faults. . . The discovery . . . reveals the southern tip of the San Andreas Fault changes fairly gradually into the ladder-like Brawley Seismic zone. The structure trends northwest, extending from the well-known main trace of the San Andreas Fault along the Salton Sea’s northeastern shore, to the newly identified East Shoreline Fault Zone on the San Andreas’ opposite edge.

. . .

Future earthquakes in that zone or near the San Andreas Fault could potentially trigger a cascade of earthquakes leading to the overdue major quake scientists expect along the southern San Andreas fault zone . . .

So, perhaps it’s good that the “Riviera” scheme never worked out.

While seismologists scramble over the area to learn more about earthquake hazards, the USGS is monitoring the local volcano situation–which includes five vents discovered in 2013–through the California Volcano Observatory.

Again, not a good place for a resort!

Featured image: 12019, at Pixabay. Public domain.

PopocatepĂ©tl: A Dangerous Volcano

August 12, 2018: I’ve just read this scientific paper (open-access, freely downloadable from Springer), written by volcanologists in easy-to-understand English, that describes just how difficult it is to manage a potentially violent volcano like PopocatepĂ©tl over a long-term “semi-crisis” like the one unfolding there today. Check it out! It really gives you good background on both the volcano and its human setting.

People in central Mexico have always felt a strong personal link with Popocatepétl, which they often call Don Goyo.

As we saw last time, when this volcano broke its five-decade silence with a VEI-2 bang in 1994, local people responded with traditional ceremonies; artists were drawn to the event; government officials took emergency measures; and scientists expanded their monitoring networks.

For almost a quarter of a century now, Don Goyo has been on center stage. People have adjusted to it and are moving on with their lives, as people always do after a natural disaster.

But scientists just updated the official hazard map (Spanish) for PopocatĂ©petl, which we’re going to take a look at in this post.

The volcanologists did reassure everybody that there is no sign of any increased or upcoming increase in activity; the volcano is still at a “Yellow, Phase 2” alert level.

Also, to counter popular rumors, they stated in no uncertain terms that Don Goyo is not connected to Guatemala’s Fuego, which recently had a deadly eruption, or to Kilauea, out in Hawaii, with its spectacular lava flows. Each of these three volcanoes has its own plumbing system and exists for different geological reasons.

The problem with Popocatépetl is that, not only in 1994 but also at any point in modern times, this volcano has never shown the levels of violence that the geologic record proves that it is capable of.

And now Don Goyo has 25 million human neighbors, unfamiliar with its historic power and living less than 65 miles (100 km) away from its summit.

Ashfall risk from Popocatépetl

Ashfall risk for Popo

See CENAPRED’s hazard map (Spanish) for details. “Ciudad de MĂ©xico” is Mexico City.

  • The dotted line shows the area that would get at least 4 inches (10 cm) of ash if Don Goyo had another eruption as powerful as one about 14,000 years ago.
  • Red: In a big eruption, this unfortunate area could get lots of volcanic ash (up to yards/meters in depth) as well as a bombardment of rocks up to a foot (30 cm) in size.
  • Orange: Just a little ash would fall here in a small eruption, but up to 3 feet (1 meter) or more in a big one.
  • Yellow: This region isn’t at much risk of ashfall in small eruptions at PopocatepĂ©tl, but it could get several inches (dozens of centimeters) in a large eruption.

Seismic sensors, deformation monitoring, and gas/hydrothermal studies can pick up signs of such approaching events, especially the big ones.
Continue reading

Mount Rainier

This was first published at my other blog on May 3, 2014.

There is a king in the Pacific Northwest, his brow crowned in glittering ice.

Mount Rainier starts to rise only about 25 miles from the Seattle-Tacoma metropolitan area. Today this beautiful Cascades stratovolcano, towering 14,410 feet above Puget Sound, dominates the skyline of towns and cities that sit on material that once made Rainier almost 2000 feet taller.

Flank Collapse

About 5600 years ago, around the time when the ancient Egyptians were getting organized, Mount Rainier’s northeast flank and summit collapsed. It was dramatic even as described by scientists, who say that a cubic mile (4 cubic kilometers) of flank and summit material (now called the Osceola Mudflow):

…washed across Steamboat Prow and Glacier Basin and then ran up to about the 6400-foot level of Goat Island Mountain and Sunrise Ridge. It then descended the White River valley 80 to 150 m (260- 490 ft) deep, spread out over 210 km2 (82 mi2) of Puget Sound Lowland 70-100 km (44-62 mi) from source, and flowed into Puget Sound, moving underwater up to 20 km (12.4 mi) to the present sites of Tacoma and the Seattle suburb of Kent. The contemporaneous phreatic and phreatomagmatic explosive eruptions blew hydrothermal clay and mud northeastward across Sunrise Ridge and spread pumice across an arc from south to northeast of the volcano. The Osceola edifice collapse left a horseshoe-shaped crater open to the northeast at Mount Rainier, much like the open crater formed at Mount St. Helens in 1980.

Mount St. Helens composite image by Ewen Roberts

Mount St. Helens composite image by Ewen Roberts.

Geologists believe that this collapse happened because the rock had been weakened by the circulation of hot, acidic water inside the volcanic structure. Over time, through many eruptions, Rainier built itself back up into the majestic but dangerous structure everyone today knows and loves.

The USGS says it has seen no change in the pattern and expects Rainier to continue growing, erupting and collapsing.

Volcanic Hazards

Today, about 80,000 people are at risk from a potential mudflow, also known as a lahar, from Mount Rainier, say experts at the United States Geological Survey (PDF). This could be triggered by the sort of volcanic activity that the USGS monitoring network would pick up, but it might also happen without warning as another flank collapse. Such a collapse, say the geologists, could reach Orting, Washington, in as little as 40 minutes.

For this urgent need, an acoustic network now surrounds Rainier. Pierce County, Washington, also is developing a specific volcanic hazard plan (PDF) for Mount Rainier.

No one wants to live in fear when there is so much beauty and wonder about this monarch of the Cascades. Having recognized its dangers, people are working to minimize them so that everybody can continue to enjoy this beautiful mountain.. This requires a lot of work but, as shown in Jayson Yogi’s video of a 2011 Rainier summit climb via the Emmons Glacier, difficult struggles have their own special rewards.

Update, July 17, 2014: “Detailed imaging of Mount Rainier shows subduction zone in glorious detail.” Scott Johnson, Ars Technica.

Front Page Image of Mount Rainier is by Michael Lehenbauer.


Mount Rainier,” United States Geological Survey: Volcano Hazards Program.

“Mount Rainier – Living Safely With A Volcano In Your Back Yard.” (PDF) USGS Fact Sheet 2008-3062

Timeline — B.C.” Air War College: Contents of 12,000 Year Timeline.

“Volcanoes of the Cascades: Their Rise and Their Risks.” Richard L. Hill. Globe Pequot Press, Guilford, Connecticut. 2004.

Guest Video: Early Earthquake Warning Systems

You may have heard of earthquake warning systems. Here is how one of them works.

In that example, people in Palm Springs and along the line of the spreading rupture are out of luck, but the system definitely helps communities farther away.

Early warnings have saved many lives in Mexico, but there are limitations to what any early warning system can do.

False alarms are inevitable. Another problem is that earthquakes are unpredictable and little is known about why they occur. Seismologists, for example, wonder why Mexico experienced three major earthquakes in six months.

And local media report that the sirens are stressing people out to the point where some even hear them when they are not in operation.

A seemingly good solution to reduce anxiety would be to set your phone/alarm system to only register large-amplitude ground movement. Unfortunately, according to a recent study, early earthquake warnings work best for relatively small seismic waves.
Humanity has come a long way since a large earthquake in 1556 killed over 800,000 Chinese people, but there is still quite a way to go.

Featured Image: Andy Maguire. CC BY 2.0.

Kick-’em-Jenny Volcano on Orange Alert

Update: On March 22, UWISRC lowered the alert level to yellow, but the 1.5-kilometer exclusion zone is still in place.

Update, March 15: UWI seismic experts note that the number of quakes at the volcano is dropping. However, Kick-‘Em-Jenny has done that before and then gone on to an eruption, so they are keeping the level at orange for now.

No, seriously, that’s the name of this underwater Caribbean volcano. Here’s a post I did on it at the Clear Sight blog in 2015.

The University of the West Indies Seismic Research Centre has raised the alert level to orange again and has set up an exclusion zone. More details are available in this UPI story.

Per the Kick-’em-Jenny Global Volcanism Program page, the exact details of the current increase in activity are unspecified. A combined British/UWISRC research team recently studied the volcano.

Featured image: Lyn Topinka, USGS, via Wikimedia.

Guest Videos: Finding Megaquakes Before They Happen

On March 8, a two-month seafloor-drilling expedition set off to investigate the underwater megathrust fault that most threatens New Zealand’s North Island–the Hikurangi subduction zone.

The South Island is also at risk from its own big fault zone:

Information obtained from these investigations will help geoscientists all over the world improve their understanding of subduction zones and the deadly megathrust earthquakes they spawn.

Sometimes it is also possible to get 3D studies of a subduction zone.

The Hikurangi zone researchers also want data that will help them understand slow-slip quakes and their relationship to the damaging “fast” earthquakes that we’re all familiar with.

Featured image: US Air Force/Technical Sergeant Daniel St. Pierre.