The state of Washington contains 7 active volcanoes. These active volcanoes include
Mount Baker and Mount Saint Helens. However, not all of the volcanoes within the state are
tall stratovolcanoes. One of these lesser known volcanic fields produced three recent
eruptions northwest of the town of Stabler. These eruptions were a mixture of explosive
and effusive, but regardless would have been impressive to witness. What I am referring to
is the West Crater, which is part of a yet unnamed larger volcanic field.
This video will discuss this active volcano, and mention what its future hazards are.
The West Crater volcano can be found near the very southern edge of the west central portion
of Washington state. Specifically, it can be found 23 miles south of Mount Saint Helens,
and 17 miles northwest of the town of Carson. Due to this volcano's geographic location,
it is technically the closest active volcano to downtown Portland.
When I describe the west crater volcano, I am not just referencing the single vent which bears
that name. Rather, I am referring to a group of 13 volcanic features in the region which
seem to have a single point of origin at depth. The West Crater volcano began forming 360,000
years ago, when subduction related magma reached the surface in the region. These early eruptions
constructed a new cinder cone, which would later be known as Soda Peak. Over time, this cone grew
to more than a mile wide, and stood more than 1500 feet higher than the surrounding landscape.
The lava which erupted from this cinder cone was basaltic in composition, which meant that
lava flows from this vent moved relatively quickly and thus spread out over a large area.
20,000 years later, a new series of eruption began 4 miles to the southeast, which began
constructing a feature known as Trout Creek Hill. Unlike the prior eruption at Soda Peak,
the lava which erupted onto the surface was less siliceous and thus moved far more quickly. As a
result, these eruptions built a 3 mile wide shield volcano, with a central rounded peak,
and a gentle slope. One of the lava flows from this volcano traveled more than 12 miles to the
south and for a time dammed the Columbia River. Over the subsequent tens of thousands of years,
infrequent large volume eruptions of lava continued in the region. At depth, however,
the magma chamber which fed these eruptions was becoming more viscous. Instead of erupting basalt,
future eruptions would now erupt andesite. The first of these andesitic eruptions
created a large lava dome and related lava flows at (Sue-sawn) Siouxon Creek. Although
the area has since been heavily vegetated, and carved by glaciers, you can still find
remnants of this ancient series of eruptions. Over the next two hundred thousand years,
several other prominent peaks were formed by andesitic eruptions. Two examples include
Timbered Peak and Bare Mountain. After the end of the last ice age,
the region once again began to show signs of unrest. Then, 8000 years ago,
lava erupted onto the surface and formed a small spatter cone at Hackamore Creek. Over the course
of this eruption, the spatter cone was built to a modest height of 50 feet, and deposited 4 million
cubic yards of andesitic scoria. What had just occurred was one of the smallest eruptions of
lava on record in the entire cascade range. However, eruptive activity was not complete.
100 years later, a vent opened up 3400 feet to the southeast.
Due to the viscosity of the lava which erupted, it formed a large lava dome known as west crater. The
andesite then flowed both to the east and west, and traveled about 2.5 miles in each direction.
The most recent eruption from the West Crater occurred in 5750 BC, when a phreatic explosion
created a 1400 foot wide and 350 foot deep explosion crater near the peak of Bare Mountain.
The long eruptive history of this volcano suggests that additional eruptions will occur in the
future. The next eruption will occur somewhere in a 9 by 9 mile section of forest, which I
have outlined on screen. The next eruption could produce a lava dome OR create another explosion
crater. Regardless, as long as the area remains sparsely populated, the next eruption should not
pose much of a threat to anyone. Overall, the odds of an eruption from the West Crater are about 1 in
5000 each year. As a result of these hazards, the US Geological survey designated the West
Crater as a low threat volcanic field. I hope that you enjoyed this video. If
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