Lassen Volcanic National Park—the southernmost Cascade Range volcano
July 13, 2020
The Cascadia Subduction zone extends along the entire coast of Washington and Oregon, but also along the northern coast of California. South of Mendocino, California, the plates change from converging with each other (the ocean plate loses and slides beneath the continental plate in the subduction zone) to sliding past each other along the San Andreas fault (a transform-type plate boundary). Check out my last post, on 10 May 2020, to see maps of the entire Cascadia Subduction zone and an explanation of why volcanoes occur there.
Volcanism in the Lassen region has been ongoing for about 3.5 million years. The center of volcanism has shifted over time, as shown in the map and diagram below.
Mt Lassen erupted most recently in 1914–17. It was the youngest volcano eruption in the Cascades until Mt St Helens erupted in 1980. The results of this eruption are most visible in the Devastated Zone, which can easily be viewed from the main road through the park. But our focus in a July backpacking trip to Lassen was the eastern side of the park, where Cinder Cone was built in 1666—it must have been a big event for the native people who were living in the area at that time.
A favorite part of Lassen Volcanic National Park is Bumpass Hell, a hydrothermal feature located in the southern park of the park. The area includes roaring fumaroles (steam and volcanic-gas vents), thumping mud pots, boiling pools, and steaming ground. Water from rain and snow that falls on the highlands of the park feed the hydrothermal system. Once deep underground, the water is heated by a body of hot or molten (i.e., liquid) rock beneath Lassen Peak. Rising hot water boils to form pools and mud pots. Super-heated steam reaches the surface through fractures in the earth to form fumaroles at the surface.
Another process that formed Lassen Park is the action of glaciers during the Last Glacial Maximum about 20,000 years ago.
Lassen Volcanic National Park is one of the under-appreciated parks. It has a large variety of geologic features that make it well worth a visit, and it is possible to do short backpacking trips that enable visitors to enjoy solitary experiences.
glad you guys are still traveling, exploring and blogging. this was a nice virtual vacation for us sheltering in place in SF. maybe put this park on our list for when we get outta jail! all is well in SMP, more or less. xoxo Thompson & Billy
It’s an easy (and safe) trip from Ashland, but not too far from SF either. We do miss SMP and our wonderful neighbors there, but happy to be out of the city now.
I grew up in So. Oregon but never knew any of this about Mt. Lassen! Don’t know why my family never went camping there or why we didn’t talk about it. Thank you so much for this, Karen. You add to my understanding of the world with every Landscape entry.
Yet another example of how under-appreciated the park is! Thanks for reading.
Lovely, insightful post about your journey to Lassen. Thank you! Miss you! Love, Josie & Michael
So good to hear from you – will need to write up some more California geology!