Tuesday, October 6, 2015

Faulting, Volcanism, and Life in Northernmost California: the Tulelake Graben

Gillem's Bluff at Lava Beds National Monument
Lava Beds National Monument at the extreme north end of California is a fascinating place. It preserves hundreds of lava tubes and lava flows only a few thousand years old. It also preserves the memory of a people, the Modoc tribe, who were destroyed so settlers could raise alfalfa and potatoes. And there are lakes that formerly gave life to millions upon millions of birds. The smaller lake that persists (with human help) provides shelter for the migratory birds who remain. The lake basin below Lava Beds is protected as the Tulelake National Wildlife Refuge.
Multiple fault scarps (the shadowed terraces) cross the region north of Lava Beds National Monument
It began with faulting. The crust in this region has been stretched beyond the breaking point, and some of the fault blocks have sunk against the others, forming a series of horsts (the uplifted blocks), and one deep graben (the sunken block). The main fault scarp in the top picture is called Gillem's Bluff. One can just make out the waters of Tulelake at its base.
The faults provided an avenue for basaltic magma to reach the surface. The rough blocky a'a lava in these photographs is the Devil's Homestead flow, which emerged just over 10,000 years ago from fissures at the Fleener Chimneys in Lava Beds National Monument.
The graben became a collecting sump for waters in the Klamath River drainage. The present incarnation of Tulelake covers only about 15 square miles (five miles long and three miles wide), but the lake once extended across one hundred square miles. Diversions of the rivers that fed the lake caused vast portions of the lake to dry up and the new land was converted to agricultural fields. Not that the original European settlers particularly cared, but the lake was a critical stop where migratory birds rested and fed during their long journey between the Arctic regions and their winter homes in central and southern California. The topography literally funneled the birds through to Tulelake and  the Klamath Lakes a bit farther north. The lands here are mostly arid, and the water was a sanctuary.
The birds still come, Sandhill Cranes, Ross's and Snow Geese, Greater White-fronted Geese and many others, more than a million each year, but they face challenging conditions of overcrowding and disease, especially in dry years when there is less water and food (the lake is at the end of the receiving line in terms of water allotments). Avian cholera sometimes kills thousands of them. But they've survived, and I hope they will continue to do so.
Earthly violence in the form of earthquakes and volcanic eruptions created this strange landscape, but water made it productive and full of life. It's a fascinating place to visit, especially in spring and fall when the bird migrations peak.

Monday, October 5, 2015

Time Heals All Wounds. Or Does it Just Hide Them? The Ghosts of Nelder Grove

It's a beautiful place, really. It was one of the most serene places I've been in my travels, away from busy roads, cities, tourist traps, and most of all, crowds. We were only 10 miles from Yosemite National Park on a Sunday afternoon, yet we shared the place today with just six other people, all of whom were quietly looking up as if in a a medieval cathedral.
Sequoia groves are like that. The ancient trees are so big and so tall, so grand, that they seem to inhabit a different universe than "normal" trees. They tower above, like placid gods looking down on their earthly domain. They are the only species in their genus,  Sequoiadendron giganteum. The species, or species very much like it, once grew across the northern hemisphere. Through habitat loss, perhaps related to the ice ages, they disappeared from most of their range. Only on the western slopes of the Sierra Nevada have they survived, living in 68 isolated groves, and numbering only in the few tens of thousands (the more widespread Coast Redwoods of northwest California are related, but are classed in a different genus).
We were walking through a mountain cathedral, marveling at the beauty and size of the incredible trees, but I realized there were ghosts all around us. There were only 16 mature Sequoia trees along the trail we were following, but there were dozens of gigantic stumps. This serene forest was a shadow of its former glory. Someone had cut down these forest giants. According to the Friends of Nelder Grove, the entire grove includes just over 100 mature trees spread over 1,540 acres (2.4 square miles). There are 277 stumps hidden in the shadows. Three quarters of the trees that had survived for 2,000 years or more were cut down in a few decades, between the 1890s and 1920s.
The sad part is that the wood, though resistant to rot, is brittle and was rarely used for anything more substantial than grape stakes and shakes, even toothpicks. As much as 75% of the wood went to waste, as most of the trees shattered when they hit the ground. Loggers would build trenches filled with tree branches for the trees to have a soft landing, but to no avail.
The remaining trees have been protected since the 1920s, but they still face some serious threats. The trees are adapted to fire. Their trunks are very thick and do not readily burn, so the wildfires that would burn through the grove every decade or so would kill off saplings of other trees and clear the forest duff, but would rarely kill the Sequoia trees. The nature of the fires has been changing. The policy of the Forest Service for decades was to suppress fires at all cost, allowing the other conifers like White Fir and Sugar Pine to grow very tall, reaching the lowest branches of the giant Sequoia trees.
Sugar Pines are especially susceptible to catching fire, and the fire rises up the trunk into the crown. Crown fires can kill the Sequoia trees by destroying their foliage. So by protecting the trees from fire, we've made it easier for fire to destroy them. The situation has not been helped by the growing effects of global warming. Ongoing drought has led to super wildfires on a scale never before seen in the Sierra Nevada. Several recent fires burned through 200,000 acres or more.
The deep conifer forests threaten the Sequoia trees in a different way. The seedlings need bare soil and sunny conditions to germinate, but the thick forest instead provides shade and thick forest duff. The remaining ancient giants are not being replaced by young trees, not at a rate fast enough to guarantee the future of the grove.
At least we've reached a point where we know what many of the problems are, and steps (sometimes baby steps) are being made to preserve the future of these incredible trees. In the meantime, the Nelder Grove is a quiet treasure, a beautiful place for meditation.
The Nelder Grove is off of Sky Ranch Road, about 8 miles off of Highway 140 north of Oakhurst, just a few miles from the south entrance of Yosemite National Park. The last two miles of road are unpaved, but the gravel is well-graded. Our walk was along the Shadows of the Giants trail, but there is a network of trails throughout the grove. The Mariposa Grove in Yosemite is presently closed to visitation as the site is being renovated to improve the visitation experience and protect the trees. Of course when it is finished, the grove will still be visited by hundreds of thousands of people yearly. If you want to see a Sequoia grove the way it should be, quiet and uncrowded, check out Nelder. For more information, check out the web pages of the Friends of Nelder Grove, or this Sierra Nevada Geotourism site.

Saturday, October 3, 2015

Running Circles Around California's Greatest Volcano

From the northwest, Shasta and Shastina are two prominent peaks.
I'm going to get into rhetorical trouble for this. "Greatest" is a hugely subjective term, and there are going to be some disagreements. But Mt. Shasta is California's greatest volcano. Not necessarily my favorite (though it might be), but the greatest. How does one judge such thing? My standard of the day is topographic prominence and topographic isolation.
A gigantic debris avalanche covers the countryside for 28 miles north of Shasta.

Topographic prominence is the elevation difference between the summit and the highest or key col to a higher summit. Topographic isolation is the minimum great circle distance to a point of higher elevation. By those metrics, Mt. Whitney, the highest point in the state has the greatest prominence and isolation. It's 1,646 mi (2,649 km) to another mountain that is higher than Whitney, and it has a prominence of 10,080 ft (3072 m). But Whitney is surrounded by dozens of mountain peaks that are nearly as tall. It doesn't exactly stand out. But Mt. Shasta stands alone, with a prominence of 9,832 ft (2997 m), and it is 335 mi (539 km) to another peak that is higher (in the Sierra Nevada). In short, Shasta is a huge mountain that provides an awesome sight from all compass directions. And that's what today's pictures are about.

Last week we took four days to completely circle Shasta, first traveling north on Interstate 5 to pass by the western flank of the mountain, then following Route 97 to swing around the north side. We took Route 161 along the Oregon border to get to Tulelake and Lava Beds National Monument for a view form the northeast. We then drove over Medicine Lake Highland for a look at the south flank.
Whitney Glacier is the longest glacier in California, and the only valley glacier.

Shasta has a few other distinctions. It has the largest and longest glaciers in California (above). Whitney glacier is 2 miles (3.2 km) long, while adjacent Hotlum glacier covers 0.7 square miles (1.8 km2). Both glaciers have grown in size over the last fifty years, seemingly at odds with global warming. The growth is explained by increased precipitation over the years (from higher evaporation rates over the warmer oceans), even though temperatures in the region have increased 2-3 degrees. As warming continues, the growth spurt will end, and so probably will the glaciers themselves.
Sandhill Cranes pause in their migration at the Tulelake National Wildlife Refuge on the northeast side of Shasta
Another strange aspect of Shasta is the unusual hummocky surface that extends north from the mountain for 28 miles (43 kms), almost to the town of Yreka. The lumpy surface is the remains of a gigantic debris avalanche that destroyed a previous incarnation of Mt. Shasta around 300,000 years ago. The avalanche was not recognized for what it was until a similar event traveled 12 miles from Mt. St. Helens in the eruption of 1980. The landslide is one of the largest ever documented in the world.
Shasta from the Tulelake National Wildlife Refuge

Volcanism has been taking place at Mt. Shasta for around 600,000 years, but most of the cone-building has happened within the last 200,000 years. Shasta is actually an edifice of four different cones that formed at different times. The Sargents Ridge and Misery Hill cones are the oldest, and the least obvious. Whitney Glacier follows the edge of the Misery Hill crater.
The southeast flank of Shasta from near Bartle.

Shastina erupted around 9,700-9,500 years ago, and the main peak, Hotlum Cone, has been erupting during the last 9,000 years. The most recent volcanic episode may have been only 200 years ago. Several villages have been constructed on the flanks of the volcano, including McCloud, Weed, and Mt. Shasta City. Around 20,000 people call the volcano home.

Unless you count the Lemurians. And the Atlanteans. Such a prominent mountain could not be without legends and myths, and Shasta has plenty. Tired half-conscious climbers have reported seeing survivors of the Atlantic disaster wandering the upper slopes, and an entire cottage industry swirls around the mysticism of the mountain, and all the beings who live in gigantic underground cities within the volcano. I suppose it all makes sense...

The biggest volcano in the Cascades, the biggest volcano in California, visible for a hundred miles or more in many directions, it's a great volcano. Maybe the greatest.

Wednesday, September 30, 2015

Yesterday's Mystery Rock Explained (Sort of...)

Yesterday's mystery rock was strange. Had I not been standing on the flanks of the largest volcano in California (and possibly in the lower 48 states), I would have guessed that the rock had been formed by boring (that's as in "digging", not "uninteresting") clams or some other creature. Many of you guessed the same, and I don't blame you at all.
The easy answer, the quickest explanation is to say that this is the surface of a boulder of vesicular basalt, the term "vesicular" referring to the presence of gas bubbles that formed during the extrusion of  lava on the Earth's surface. The boulder was being used as a vehicle barrier at the pullout for the Devil's Homestead lava flow at Lava Beds National Monument. The monument covers a portion of the northern flank of Medicine Lake Highland, a huge volcanic shield complex along the boundary between the Cascade Range and the Modoc Plateau.
The thing is, I've never seen vesicles like this before. They are uniform in size and spacing. They also looked very strange from the side: they were the top of linear tubes running through the rock. I'm not even sure the tubes and vesicles are right side up. The rock had been moved into the parking area, after all, and could have been overturned in the process.
I find references to "pipe vesicles" that form when lava flows over sources of water (the pockets of steam rise through the lava), but I'm not knowledgeable enough on the subject to say that the term applies here. If the volcanologists among you want chime in, I am all ears!
Thanks for the many responses. I love a good mystery!

Tuesday, September 29, 2015

A Little Rock Mystery for the Day

A little rock mystery for the day. What are we looking at, and why is it strange? The picture is about 16 inches across.

"There Can Be Other Occupants" Wait, What? Notes from the Volcano Underworld

Yeah, that's something you want to think about while stumbling around in a dark cave. And for a government sign, that is almost eloquent. I spent the weekend exploring the flanks of the largest volcano in the Cascades, and thus, I assume, in the lower 48 states (all bets are off when we speak of Hawai'i and Alaska). It's called Medicine Lake Highland, and practically no one has ever heard of it. Chances are that it could be the next volcano to erupt in the lower 48, at which time everyone will hear of it. With at least 17 eruptions in the last 12,000 years or so, it has potential.
One of the most unique aspect of Medicine Lake Highland is the prevalence of lava tubes on the mountain. Just one flank of the volcano, preserved as Lava Beds National Monument, has around 700 individual lava tubes with a combined underground distance of more than 75 miles. A cave system within the Giant Crater Flow on the south flank of the volcano can be traced for 14 miles. That's where I was exploring yesterday.
Dot Jean Cave is part of the Giant Crater tube system. Lava tubes form when the lava flow crusts over but the lava continues to flow beneath. The tube system may eventually drain, leaving behind the caves. Dot Jean is easily accessible, just off the National Forest Road 49 a few miles from the summit area. The cave is unique because it doesn't have openings at the lower end. This means that precipitation and cold air can drain into the cave, but can't drain out. Even in summer the ice that accumulates doesn't completely melt away. The ice actually kept me from exploring very far into the cave. There was an ice cascade that would be easy to slip down and very difficult to climb back up.
 It wasn't hard to get to the large ice mass at the top of the slide though, so I made my way down, while watching for the "other occupants" of the cave. What or who on Earth were they hinting at? I guess we were pretty close to Sasquatch country, so I'll figure that's who it is.
The ice mass in the upper part of the cave is large and fairly translucent. It refracts and reflects light from the cave opening above and appears to glow with an eerie blue inner light. It's almost unsettling.
It is strange to walk through a cave that has existed for less than 11,000 years. Medicine Lake Highland is a short of hybrid shield volcano that has erupted a variety of lavas, including basalt, andesite and rhyolite. The most recent eruption was only 900 years ago, and high geothermal gradients and the occasional earthquake swarm indicate that magma still lurks within the mountain. Yes, I did indeed spend some of my time on the mountain this weekend hoping to see an eruption, but no dice. This time.

Sunday, September 27, 2015

Total Lunar Eclipse, Blood Moon...and the World Didn't End

I had a nice perspective on the Blood Moon Lunar Eclipse tonight from my vantage point in the parking lot of the Olive Garden in Redding, California. Mrs. Geotripper tried to be patient when I got up every 15 minutes to go outside and take another picture.
We didn't get to see the beginning of the eclipse out here on the west coast, or at least I didn't as I was driving down the mountain road from Lassen Volcanic National Park, and couldn't see the moon at all until after 8:00 PM. The boundary zone between the Sierra Nevada and Cascades is a rather prominent visual blocker to things on the eastern horizon. But we sure had a nice sunset at Manzanita Lake (see below).
The moon appears red during the highest totality because sunlight is refracted through the Earth's atmosphere and shines across the surface of the Moon. If we had no atmosphere, the Moon would go completely dark during totality. 
Columbus didn't discover that the world was round. That fact was known thousands of years ago from the shape of the Earth's shadow across the face of the Moon. One of my favorite teaching moments took place a few years ago when I asked an earth science class if they could prove that the Earth was spherical. They didn't do all that well ("we have pictures from space!"), so we all went outside and looked at an ongoing lunar eclipse!
The world didn't end (at least not yet). I always get irritated at religious claims about the end times that pop up at moments like this. I'm truly sorry that people can be so gullible about this sort of thing. If one is going to be convinced about their particular religion's claims that the world will end because of a lunar eclipse (or comet, or solar eclipse, or whatever), it's like saying that the sun is predicted to rise tomorrow and therefore the world will end. If a phenomenon is going to be convincing as a sign from God or the gods, then it should be totally unexpected. Like a solar eclipse when the moon is in some other part of the sky. Or the sun coming up in the west. Or planets changing the direction of their orbit. That would be worthy of attention.
This, by the way, is why I wasn't in some place with a view of the eastern horizon. The sunset on Lassen Peak at Manzanita Lake kind of distracted us. A little.