Monday, July 4, 2011

A Convergence of Wonders: Day 2, Lava Beds and Newberry Caldera

A Convergence of Wonders is a chronicle of our recent journey through the Pacific Northwest and Northern Rocky Mountains. This the second day's story...
What is that blazing orange light interrupting my slumber?? June 16 dawned very early, with twilight beginning around 4:30 AM, and sunrise about 5:20. I was up for good at that point. There was no sleeping in the brightness; tents don't insulate you from the outdoors as well as solid walls. I've always loved dawn at Lava Beds National Monument, though. The sky is as big there as any place I know, with far-off horizons and clear air.

Our day was going to be spent on the two largest volcanoes of the Cascades, and hardly anyone has heard of either of them: Medicine Lake Highland, and Newberry Caldera. Crater Lake was slated to be on the day's menu, but 10-12 feet of snow still coated the rim, and we just weren't going to see it this time around. Both Medicine Lake and Newberry have been called basaltic shield volcanoes, but they are more complicated than "normal" shields with a variety of lava and magma compositions and are described as "shield-shaped volcanoes". We started the day on the flank of Medicine Lake Highland, but we couldn't actually see the volcano until mid-day, when we were far enough away. It is the largest single volcano in the Cascades with a volume of around 130 cubic miles (Shasta has around 85-100 cubic miles).

The best known part of Medicine Lake Highland is Lava Beds National Monument, where we spent the night. The park preserves a series of basalt flows that developed a network of lava tubes, underground conduits that allowed the basaltic lavas to flow for miles before cooling. The tubes drained at the end of the eruption, leaving a series of caves. Lava Beds preserves the largest concentration of lava tubes in North America, in excess of 700, with a combined length of more than 30 miles.

The students had explored a few of the lava tubes the previous night, so we sampled just two in the morning. Valentine Cave is in a separate younger flow, and is remarkably clear of debris and easy to walk through (the CCC cleared much of the talus in the 1930s). It has most of the interesting cave features such as lavacicles, bathtub rings (lava benches), rafted boulders, lava falls, and pahoehoe flows on the cave floor.
Outside the caves, there were an unusual number of wildflowers in evidence, given the long spring and cooler temperatures. This is an Indian Paintbrush on the flank of Mammoth Crater, the source for more than two-thirds of the lava flows in Lava Beds.
After a visit to the Visitor Center, where we were certified as free of white nose syndrome (this is a horrific bat disease, not a human one), we went to the more ominous sounding Skull Cave. The name is like something out of a campy adventure movie, and the reality is also kind of frightening. Skull is a cave with multiple levels, and the first drop to the second level down is just within the zone of total darkness. Animals and a few humans without sources of light would move into the cave, looking for water maybe, and just as it got dark they would step over the side into the abyss (literally and figuratively). Today there is a metal stairway to negotiate the dropoff, and we explored the icy depths (literally icy; water sinks into the cave in the winter, freezes, and stays there, even in summer).

Skull has the largest opening of any cave in the park because it is part of the main feeder tube that transported the lava for 10-15 miles. Unlike the smaller caves, the main tube is relatively unstable, and huge blocks of basalt have broken off the ceiling and littered the cave floor to the extent that few original flow features are visible. It was so large I half-expected to see Han Solo, the Millenium Falcon, and a giant space worm in there.
Our next stop was more sobering. California was never kind to the hundreds of native cultures that existed prior to the Mission era and the Gold Rush. Many were slaughtered or sickened to extinction without leaving any kind of record. The Modoc culture was destroyed, but not without a fight. Lava Beds was the site of the last battles between the U.S. military and native peoples in California, in 1872-1873. Despite being outnumbered as much as 10-1, the Modoc people held out for five months.
I've provided a detailed commentary on the battles that took place in my Other California series about Lava Beds. In short, the Modocs held the advantage of knowing the territory, and of taking shelter at Captain Jack's Stronghold, a natural fortress that was almost impossible to take as long as there were a few armed defenders. Pressure ridges and schollendomes provided the trenchs and "castle" walls that made the stronghold practically impregnable.
A fire swept through the Stronghold and much of the northern part of Lava Beds a few years ago, leaving just a few Junipers unscathed. Being the only trees for some distance, a lot of birds were in evidence, including a pair of juvenile Great Horned Owls.
Why do owls always look so perturbed? I suppose a bunch of tourists with cameras had something to do with it...
We moved on to an outlier of the park, a deeply eroded tuffaceous cone called Petroglyph Point. The cone had erupted in the midst of Tule Lake, and the yellow layers of tuff had been deeply eroded by waves on the lake, forming a striking west-facing cliff punctuated by tafoni, hollows formed by weathering. One can see the wave-cut notches running along the base of the cliff behind the chain-link fences. Why are the fences there? Oh yeah, petroglyphs. Petroglyph Point is the largest panel of petroglyphs in the country...
Most of the rock carvings in the cliff predate the Modocs. The lake lapped at the base of the cliff, and the artists would have required rafts or canoes to reach the site. Because the lake has been mostly diverted and dried up for agricultural purposes, blowing sand and dust threatens the integrity of the rock art. See more info on the panel here.
We were finally far enough away to see the full extent of the Cascade's largest volcano, by volume. Medicine Lake Highland is the broad gently sloping dome on the horizon. Mt. Shasta can be seen on the right skyline (click on the photo for an enlarged view).
Then came one of the dreaded "pushes". We had to put about 170 miles between us and our next destination, Newberry Volcano. Oregon has some pretty volcanoes, including Mt. Theilsen and Mt. McLaughlin, but they were only occasionally visible between stretches of dense forest. The road was very straight and monotonous after Klamath Lake. Eventually though, we arrived at Newberry Caldera, a shield-like volcano similar in many respects to Medicine Lake Highland. We also found a wall of snow. The bathrooms were unavailable, the camp we had reserved months earlier was not open yet (fortunately I knew this and had made alternate arrangements), and there was no official parking available to see our main site, the obsidian dome. We made do, and most of the students hoofed it over the snowbanks to see the obsidian up close (more than a few snowballs were launched as well).
I crossed the highway and climbed the hill to get a better perspective on the dome. Mountains like Newberry and Medicine Lake have multiple magma sources, probably because very hot deep mantle source basalts melt some of the more silica-rich continental crust. The volcanoes spew out plenty of highly fluid basalt flows, but also occasionally produce much stickier rhyolite flows, forming small plug domes. The rhyolite lava often forms obsidian and pumice, as it did here.
We were in the midst of a caldera on the summit of Newberry. A caldera forms from the collapse of the top of a volcano due to the withdrawal of magma during eruption sequences. Paulina Peaks on the rim of the caldera loomed high above us while we hiked through the snow. Crater Lake (which we were not able to visit) is one of the world's best examples of a recently formed caldera. The catastrophic explosion that accompanied Crater Lake's origin probably did not happen at Newberry. The caldera development was more gradual and less explosive.
We were ready to get to camp, and traveled the final 30 miles as quickly as we could. We set up in the group site at Tumalo State Park, a pleasant site just outside Bend, Oregon. The evening was nice enough, but somehow overnight, the temperature dropped to 28 degrees. This is summer??
On day three, we head for the coast and for great disappointment (this sentence has multiple meanings, as you will see).

3 comments:

Gaelyn said...

Newberry Crater is so diverse. I really like walking on the hills of obsidian and River Cave is a very big lava tube. Fun trip so far, except for the snow and cold.

Ron Schott said...

In many trips up and down California I've never made it to Medicine Lake. Is there a good geologic map or guidebook for my next trip?

Garry Hayes said...

Resources on Lava Beds and Medicine Lake Highland:

http://www.nps.gov/labe/planyourvisit/upload/Visitor%20Guide%20to%20the%20Medicine%20Lake%20Highlands.pdf

http://www.siskiyous.edu/class/geol62/MLVtext2008.pdf

http://www.cr.nps.gov/history/online_books/geology/publications/circ/838/roadlog7.htm

I also edited a field guide for Lava Beds for the fall 2007 meeting, available from NAGT here: http://nagt-fws.org/publications.html