I’ve said there are just two Cascade Range volcanoes in California—Mt. Lassen and Mt. Shasta. But there is a third called Medicine Lake Volcano, as shown on the map below (from https://en.wikipedia.org/wiki/Cascade_Volcanoes). Lava Beds National Monument is located just north of the volcano, where numerous flows have completely covered the landscape during the past 500,000 years.
Because it is a shield volcano, like the volcanoes in Hawaii, the Medicine Lake volcano is not as obvious in the landscape as the classic-shaped composite (or strata) cones like Shasta and Lassen . Shield volcanoes have a low profile because the lava forms from silica-poor magma (mostly basalt) that is more fluid and can’t hold up steep-sided cones like their composite cousins with more sticky, thick eruptive materials formed from magma richer in silica. The photo below (view to SW from Schonchin Butte) shows the western half of the Medicine Lake volcano with many cinder cones of various ages on its flank. One is obviously very young because it lacks any vegetation. In contrast, Mt. Shasta in the background (right side of photo) has steeper slopes and an overall higher elevation. Although Medicine Lake volcano may not look as impressive, by volume it is the largest Cascade Range volcano!
Why is the Medicine Lake volcano different than the other Cascade Range volcanoes? Because it is at the intersection of the Cascade Ranges and the Basin and Range province, where normal faults are causing Earth’s crust to be pulled apart and where avenues are provided for magma to travel more directly from deeper depths (the mantle), without as much mixing with the silica-rich continental crust. The photo below (view to the NW from Schonchin Butte; taken by Jay Ach) shows Gillem bluff, which is a fault block that has been uplifted and tilted westward (left side of photo) relative to the down-dropped block to the east that is occupied by Tule Lake and agricultural fields. The dark area in front of Gillem bluff is the Devil’s Homestead flow that erupted about 10,000 years ago.
The Medicine Lake volcano has had eruptions of more silica-rich magmas—for example, Glass Mountain on the eastern flank, where a ~950-year-old eruption produced extensive obsidian flows. But at Lava Beds, most of the lavas are basalt that form a wide variety of small cones and flow types. Just like in Hawaii, visitors can see rope-like “pahoehoe” lava (photo below) that forms when the lava is very hot and flowing freely.
When the lava is cooler and flowing more slowly, it forms “aa” lava. In the photo below, Jay is saying “ah-ah” as he tries to walk across the very rough Devil’s Homestead flow.
Most of the flows in Lava Beds emanated from Mammoth Crater, an impressive hole-in-the-ground at the southern end of the park, where the Big Nasty Trail provides an interesting 2-mile-long excursion across lava that is really not all that nasty.
A map in the Visitors Center, located near the Mushpot Cave, shows how lava from Mammoth Crater has flowed north across the landscape. It also shows where the most popular caves are located.
In addition to cinder cones, there are “spatter cones”. It is fun to imagine blobs of hot lava being spewed from a hole in the ground and being slapped onto a growing pile. This spatter cone (with Karen for scale; photo taken by Jay Ach) is located on the Big Nasty Trail.
The main attraction of Lava Beds is the lava tubes that form a wide variety of caves ranging from easy (i.e., one can walk upright) to difficult (i.e., it’s necessary to crawl through some parts). We elected to stick to the easier caves, which still provided lots of interesting features. Good lights are necessary in all caves; for protection, hard hats and warmer clothing are useful in some caves. Below is a photo of Jay and me at the entrance of Valentine Cave, our favorite because of the large variety of lava features, including canals along the tube edges that formed by fast-flowing lava as it moved through. Note the “lava stalactites” that formed on the tube’s roof by the bits of lava that lingered after the flow had continued farther downhill.
Also visible in Valentine cave is lava “frozen” in place while flowing through the tube. It is easy to imagine the lava when it was actively flowing. The photo was taken by Jay using “light painting” to illuminate the space.
The bleakness of the landscape was punctuated by the colors of wild flowers in the month of June when we visited the park. We particularly liked the penstemon flower with its brilliant purple-blue color. The photo was taken along the Big Nasty Trail.
Others interesting features of the park are the desert vegetation and the sky. The photo below was taken by Jay in the campground as the sun was setting, using some clever lighting techniques. The trees are junipers.
The night sky is particularly stunning in this location far from any city. Jay took this photo of the Milky Way in the campground, again using clever lighting techniques to show the trees and the sky in the middle of the night.
It was close to a new moon during our visit, which helped make stars in the night sky even more clear. Jay took this photo just before sunrise; the planet of Venus is also prominent in the sky. The disk of the moon is only visible because of the long exposure.