A Tour of the Cascade Volcanoes from Space: Washington

Earlier this month, we visited the Cascade Range volcanoes on British Columbia. Today we're hitting the volcanoes in Washington, including likely the most famous volcano (after Yellowstone) in the United States as well as a contender for the most powerful (known) eruption in the Cascades. All the images come from the Sentinel-2 Earth observing missions launched by the European Space Agency. This missions will become even more vital for monitoring the planet after NASA's Terra and Aqua satellite reach the end of their operational life in the near future. Remember, if you want to see the full resolution version of these images, I put them here.

The first potentially active Cascade volcano in the US, Mt. Baker is also one that shows off that it is far from extinct. Occasionally this volcano near Bellingham will show off a small fumarole (hot gas vent) that will get people's attention. This is all part of the hot springs and hydrothermal vents at the summit area of Baker, likely driven by magma that intruded under the volcano in the 1970s. These features are also the cause of the impressive (and dangerous) ice caves on the volcano.

The last confirmed eruption of Mt. Baker was only 144 years ago and during the 1800s, it erupted at least nine times! Most of these eruptions were relatively small, only ranking as VEI 2-3 eruptions. However, evidence exists for at least one larger eruption at Baker in the past 10,000 years.

However, Baker itself is part of a larger, long-lived volcano field that dates back to over 1 million years ago and includes the Kulshan Caldera. The explosive eruption that formed the caldera 1.15 million years ago was on par with the Crater Lake-forming eruption of Mt. Mazama (~50 cubic kilometers).

Since then, the numerous eruptions in the area have moved to the southwest creating a series of volcanic features like lava domes and flows, as well as explosive and lahar (volcanic mudlfow) deposits. The latter are the biggest hazard for people living near Baker. The abundant snow and ice on the volcano leave a high potential for mudflows that could inundate towns along two major rivers to the west of the volcano. Even with all the potential threat from a new Baker eruption, the monitoring infrastructure at the volcano needs a big improvement as to keep people in the region safe.

If the Cascade Range has a dark horse, it is Glacier Peak. Located in the wilderness south of Baker and northeast of Seattle, many people don't even know the volcano is there. As the name suggests, Glacier Peak has a dozen glaciers and has been beaten up by glaciers during the last Ice Age, so it has a craggy complexion.

Yet, Glacier Peak is the source of one of the most explosive Cascade eruptions in the last few thousand years. Ash from the eruption ~13,000 years ago can be identified into Montana and the Great Plains. Only 1,800 years ago, the volcano produced a series of explosive eruptions likely caused by collapsing lava domes (much like Mount St. Helens or Russia's Shiveluch). All this explosive activity also triggered mudflows that traveled tens of miles down the river valleys leading from the volcano's many glaciers.

Even if Glacier Peak isn't high on most people's list, it has only been ~224 years since its last confirmed eruption. That was only one of a series of eruptive periods the volcano has experienced over the last 5,000 years. A big explosive eruption from Glacier Peak could wreak havoc on air travel over the western United States if lots of ash is thrown up into the stratosphere.

Rainier might not be the biggest volcano in the Cascades, it is definitely the meanest. Even when it is not erupting, it has unleashed giant lahars that reached Puget Sound and dozens have people have perished over the last century on its ice-laden and crumbling slopes. It looms over Seattle as a constant reminder that, yes, the Pacific Northwest is a highly geologically active place to live.

Exactly when the last eruption at Rainier is unclear. There were many reports of potential small eruptions from the volcano across the 1800s, but none have been confirmed. Many of those might have been phreatic - that is, steam driven - rather than caused by magma. The most recent confirmed eruption was around 1450 CE and the volcano produced a VEI 4 explosive eruption ~2200 years ago. However, the most devastating events at Rainier over the last 10,000 years are like the volcanic mudflows like the Electron mudflow that happened ~500 years ago.

It is not an exaggeration to say that a major eruption of Rainier could be catastrophic for the cities on the east side of Puget Sound. The potential for mudflows and ash fall that could last months to years would disrupt air, rail and road traffic along the I-5 corridor. The highly weathered nature of Rainier thanks to all the hydrothermal and glacial activity means that an eruption could lead to collapses of parts of the volcano's slopes. If Rainier starts getting restless, we all better take it seriously.

Mount St. Helens is the teen idol of the Cascade Range. One of the range's youngest volcanoes, it is also one of the most active. It also doesn't play by the rules as it sits to the west of the main line of Cascade volcanoes (and we're not entirely sure why). Most people are familiar with the volcano's famous 1980 eruption, but the volcano was erupting as recently as 2008. Mount St. Helens tends to be rocked by short earthquake swarms that emphasize the restless nature of the magmatic system under the volcano.

Of course, from space, the most prominent feature at Mount St. Helens is the massive north-facing crater, the scar of the catastrophic May 18, 1980 eruption. Much of the landscape north of the edifice has ecologically recovered, but many of the results of the eruption are still present, like the dead trees on Spirit Lake. You can also see the lava dome on the south side of the crater where lava oozed out in 1980-86 and 2004-08.

Even though St. Helens looks so odd today compared to the other Cascade volcanoes, it may well return to more conical shape over thousands of years. Lots of volcanoes around the planet show evidence that they experienced major collapses but those scars healed with later lavas and debris. In fact, when we get to the California Cascades, we'll see one of the biggest collapse avalanches deposits on Earth, but you'd never guess it looking at its source.

Located almost due east of Mount St. Helens, I always think about the experience of the hikers who were at the summit of Adams when its neighbor erupted in May 1980. Imagine standing on top of a volcano only to see the next nearest volcano blowing its top off in cataclysmic fashion. It would both be awe-inspiring and, at the same time, disconcerting as you question the ground beneath your feet.

Mount Adams isn't nearly as active as Mount St. Helens. The last confirmed eruption from Adams was around 950 CE but it likely produced over a dozen eruptions in the last ~10,000 years. One of the most unique features of Adams is its long lava flows, some of which reached ~6 miles from Adams summit.

Even if Adams isn't as active at its petulant sibling to the west, it makes it up in shear size. It has erupted more lava and tephra than any other Cascade volcano except California's Mount Shasta over the last 1 million years. Much like most Cascade volcanoes in Washington, the biggest danger it poses is avalanches and mudflows, many of which can be triggered by events that are decidedly not volcanic -- heavy rains, earthquakes or even just gravity acting on the weakened rocks of Mount Adams.

Two smaller volcanic areas exist just to the south of Mount St. Helens. Although West Crater and Indian Heaven might look like remnants of a distant volcanic past, they are still watched by the Cascade Volcano Observatory. Both are considered low threats, but West Crater last erupted around 8,000 years ago while Indian Heaven may have erupted as recently as 9,000 years ago.

That's it for the Washington Cascade volcanoes. Next time, I'll take us through the complicated Oregon Cascades, from Mt. Hood to Crater Lake.

* so, in the previous post, I mentioned I'd be using the indigenous names for many of these volcanoes. Well, it turns out that is ... complicated. In doing some more research on these names, it sometimes isn't entirely clear what is the "indigenous" name and what are names attributed to indigenous people by non-indigenous writers. I will still list what is thought to be the indigenous name, but but I'll have some more to say on this when I write about Oregon's volcanoes.