Thursday, October 31, 2013

You Think Your Halloween Monsters are Scary? Imagine What Your Ancestors Thought About These Terrifyingly Real Beasts...

(Modified from my post of June 8, 2011)

Happy or scary All Saint's Eve or Halloween, whatever your pleasure might be. As you cheer on the zombies and alien predators extorting candy from you, give a few thoughts about what would have been really scary: the terrifying animals that humans lived with many centuries ago.

Have you ever wondered why shadows are so effective in the best horror movies? It's pretty clear to me that there is a collective genetic memory in all of us of the monsters that we think of as myths today, but which were horribly real as recently as 12,000-13,000 years ago. The world was full of creatures that wouldn't have minded dining on us, and deep in our collective consciousness is a reflexive response to particular shapes and shadows. The pareidolia I wrote of once was a survival mechanism; we needed to see those faces in the underbrush in time to climb or flee to safety.
So who belonged to that mysterious shadow above? It was a short-faced bear, Arctodus simus, that lived in my home region, the Central Valley of California. Grizzly bears were a common presence in California when the Europeans arrived two hundred years ago. They described many of the native Californians as bearing wounds of encounters with the grizzlies, and compared to spears or arrows their guns were not much better as a defense against them. The short-faced bear was bigger, maybe 2,000 lbs or more. It may have been the largest mammalian predator ever.
There were roving packs of Dire Wolves, Canis dirus, as large or larger than their cousins in Canada or Alaska...
...and there were the Saber-tooth Cats, Smilodon fatalis, (below) along with the American Cheetah (Myracinonyx sp.)  and the Scimitar Cat (Homotherium serum). We have been living with the comforting insulation of modern civilization for a long time, but even a glance at a skeleton of these long extinct creatures can awaken nightmares in the recesses of our brains.
This museum display in Sydney gave me the willies...
If you want to see the rest of these creatures in a slightly less threatening atmosphere, check out the Fossil Discovery Center of Madera County, which opened for business a few years ago. The fossil creatures on display were found by the bulldozers of the Fairmead Waste Facility. They were digging a garbage dump, and found a treasure trove of fossil bones; 27 species of mammals and a half dozen other creatures dating from the Pleistocene. I find it to be a wonderful science resource for the region. It is well worth a visit.

Fossil Discovery Center of Madera County

19450 Avenue 21 ½
Chowchilla, CA 93610

Take the Hwy 99 Exit 164, SW corner of Road 19 ½ & Avenue 21 ½

Wednesday, October 30, 2013

That Volcano is Dead Right? There's No More Hot Magma? Bumpass Hell at Lassen Volcanic National Park

"Now, I don't know,  I don't know where I'm a gonna go, when the volcano blow"
Jimmy Buffett

Mt. Tehama is long gone, and Lassen Peak blew off all her accumulated stresses and frustrations with the eruption in 194-17, right? I mean, it's all a national park now, and that means it's like an amusement park and the park service would never allow the volcano to go erupting on all the tourists, right?

Actually, the Lassen Volcanic Center is on the short list of the most likely sites of volcanic activity in California, according the the California Volcano Observatory. And there is plenty of evidence that hot magma still lurks beneath the surface in the national park: there are five active geothermal areas in the park boundaries.
It was the last day and the last stop of our late September field studies adventure through the Cascades of Northern California. We had explored the Castle Crags, Mt. Shasta, Lava Beds National Monument, Medicine Lake Highland, and McArthur-Burney Falls, as well as Chaos Crags, Lassen Peak, and Mt. Tehama in Lassen Volcanic National Park. Our destination was Bumpass Hell, at the end of a spectacular 1-1/2 mile hike.
Bumpass Hell was named after an early pioneer rancher in the area, Kendall Bumpass who had good reason to call this place his hell: he inadvertently put his leg through a thin crust of silica and plunged it into the boiling acidic water beneath. He eventually lost the leg.
Being the most active geothermal area in the park, one might think that Bumpass Hell sits atop the magma chamber, but it actually lies a mile or two east of the body of molten rock (which sits at a depth of about 3 miles). Water at depth is heated until it turns to steam at temperatures exceeding 400 degrees, and the steam rises along fractures and fault lines where it condenses and reacts with local pockets of groundwater. The water is general highly acidic, and emerges at the boiling temperature (as discovered by Bumpass and numerous careless tourists who choose not to heed caution signs).
In a general way there are four kinds of geothermal features, and three of them can be viewed at Bumpass Hell. If it is the dry season, there might not be very much water and the vents will be filled with the clay and mud formed from the decomposition of the surrounding andesitic volcanic rock. The mucky cauldrons are called boiling mudpots. These acidic pits are definitely not recommended for facial care schemes.

The black sludge in the picture below is made of finely divided particles of iron pyrite (fool's gold). That might be counter-intuitive given the familiar brassy luster of the mineral, but geology lab students will recall that the streak (color of the powder of a mineral) is black.
More familiar features are hot springs. Hot springs can be found in many geologic settings, including along fault lines, but volcanic hot springs are in a class by themselves. They are not the kind of springs that one would want to be soaking in. The temperatures at Bumpass Hell are at the boiling point, and as previously noted, the water is highly acidic.
If there is not very much water available, for instance in the late summer or fall, steam vents will be common. They are called fumaroles. Fumaroles are a good spot to see sulfur crystals growing (see the picture below). At the top of my list of worst possible jobs would be that of sulfur miner. I've seen articles on mine workers in South America who have to climb into volcanic craters and scrape off the sulfur crystals from active fumaroles, risking scalding burns and the scarring their lungs by breathing in the acid-rich air.
The only type of geothermal feature that is not found at Lassen Volcanic National Park is a geyser. Geysers like those found at Yellowstone National Park (where something like 70% of all the world's geysers are found) require very specific conditions underground that are not present at Lassen. The main reason is probably that the rocks and magmas at Lassen are not as silica-rich as those at Yellowstone. The groundwater plumbing maze beneath Yellowstone is coated with silica deposits which produced a closed system in which the pressures can build high enough to produce the spouting fountains. There are too many "holes" in the plumbing at Lassen.
Does the presence of magma underground at Lassen mean that an eruption is coming soon? It's hard to say. It may be that the eruption of Lassen in 1914-17 really did relieve pressure and stress in the magma system and that the magma today is simply cooling off and solidifying. This is suggested by the relative rarity of eruptions at Lassen (the recent event, Chaos Crags a thousand years ago, and the formation of Lassen around 28,000 years ago). But it could also be that the magma chamber still has an eruption or two left in it. In any case, we can be fairly confident that we will know something is afoot, because magmas don't sneak up to the surface without causing other forms of mayhem, such as earthquakes, changes in ground elevations, gas emissions, and increased geothermal activity.

I'll be watching. And when everyone else is running away from the eruption, me and lots of other geologists will be trying to get closer!

I hope you've enjoyed this little vignette on the Cascades of Northern California. Look for an exploration of the central coast of California next!

Tuesday, October 29, 2013

The Mountain That No Climber Can Ever Summit: Mt. Tehama (the Brokeoff Volcano)

The gigantic boulder is a glacial erratic, left behind by sheets of ice that once covered the Lassen region.
After being slightly distracted by ducks and the beautiful fall day in Yosemite, Geotripper is back on track to finish up his exploration of the Cascades volcanoes of Northern California. It was already approaching noon of our last day on the road back at the end of September, and we had six hours of driving ahead, so our list of features we were investigating was becoming short. In fact, one of the features we were interested in just simply wasn't there.

Mt. Tehama, or the Brokeoff Volcano, began erupting around 600,000 years ago just south of the present-day site of Lassen Peak. It was a stratovolcano similar to Mt. Shasta or Mt. Hood, composed mainly of gray andesite with interbedded ash and lava flows. The mountain alternated between explosive eruptions and effusive eruptions and eventually grew to a height in excess of 11,000 feet, hundreds of feet higher than modern Lassen Peak (10,457 feet).
There is a pretty good reason that mountain climbers can never summit Mt. Tehama, though. It's not there anymore. Around 400,000 years ago the magma chamber under the mountain ended volcanic activity. There has been debate about whether the mountain ended with a tantrum or a whimper, but the consensus seems to lie with the latter. The volcano stopped erupting and chemical weathering, river and glacial activity tore it apart. All that remains are a series of lower peaks surrounding the original throat of the volcano including Brokeoff Mountain, Mt. Diller, Eagle Peak and Diamond Peak.
 In the aftermath of the eruptive cycle that ended activity at Tehama, several plug domes erupted and grew on the flanks of the older mountain, including Lassen Peak itself about 28,000 years ago. Hot rock continues to simmer beneath the complex, evidenced by the recent (1914-1917) eruption of Lassen Peak, and the presence of geothermal systems like Bumpass Hell and the Sulphur Works.

From the Bumpass Hell trail, the peaks of Brokeoff Mountain and Mt. Diller seem to provide a near-perfect profile of the long-gone volcano, but the original edifice was much larger, something like 15 miles around. The center of the volcano was in the foreground and the two peaks were just part of the western flank. An aerial photograph of the mountain (from a Canada flight in 2005) offers a different perspective...

I annotated a version of the picture for a previous post on the volcano, and it is reproduced below. I'm mostly satisfied with it, although the height of the peak may be a bit exaggerated. In any case, good luck climbing to the summit!

Up next, the final stop of our trip!

Sunday, October 27, 2013

The Way it Was Yesterday: Yosemite Valley in Autumn

One of my greatest pleasures is the opportunity that I have of living only a two hour drive from Yosemite Valley. Many places in the world are on my bucket list, and I've managed to see a lot of them over the years, but for many of them the visit is short and will probably happen only once in my life. At Yosemite, I get the chance to explore and revisit places throughout the year. I joke sometimes that my favorite time of the year in Yosemite is the time that I happen to be there, but autumn is truly special.
Yosemite may not have millions of acres of deciduous forests like those in the eastern United States (and the fall colors of such places are on my bucket list), but the valley offers plenty of colorful trees and shrubs with gigantic cliffs as a backdrop, and the calm still pools of the Merced River as a reflecting mirror.
As I mentioned in the previous post, we discovered a nice little spot on the Merced River across from the sheer cliff of El Capitan. I don't think I've captured it before mirrored in the river as it is in the photos above.
 We moved up the road a bit to the Swinging Bridge Parking Lot, which was full of people as usual, but it wasn't hard to wander across the bridge and leave most of them behind. Above is a shot of Yosemite Falls (minus the water, of course) with the Merced River in the foreground.
Behind me on the southwest side of the valley were the cliffs of Taft Point and Sentinel Rock. The rocks are rugged and amazingly steep, but sometimes receive a bit less attention with Yosemite Falls just across the river.
Half Dome wasn't yet visible, but we could see the high peak of Clouds Rest at the upper end of the valley, along with Washington Column and the steep cliffs below Half Dome.
To the west were the cliffs of the Three Brothers. The largest rockfall in modern times thundered off the cliffs there in 1987, when 600,000 cubic yards fell onto the valley floor. No one was injured, but the road was blocked for a while. If you want to know a bit more about this rockfall and others, check out my roadside guide to the geology of Yosemite Valley over at Geotripper Images.
Looming high above Swinging Bridge is the towering spire of Sentinel Rock. It's not so easy to climb, but Sentinel Dome lies behind it, and is accessible by an easy trail from the Glacier Point Road. I recommend it, but I have a feeling that with the first substantial storm coming in tomorrow or Tuesday, you might have to wait until next summer to check it out!
Our next stop was Sentinel Bridge for one of the most iconic views of Half Dome. Autumn is one of the best times of the year for photographs as the river is low and calm, providing wonderful reflections. Sometimes, though, I just don't get the moronic things that people do. I cropped it out, but someone had tied a swing rope to a tree on the left side of the river. I tried to pull it down, but couldn't, so there it remains. I'll see if someone removes it before next week when I come up with the students from my Earth Science course.

The other side of the bridge offers a nice view down the valley towards Yosemite Falls, and on that side another idiot had strung a rope across the river, and was trying to cross the river in a hammock kind of thing. He was having problems with his contraption, and I am glad to report that he sploshed into the river. I would have liked it even more if a ranger had happened by and ticketed him for something or another. Recreation is great, but don't do it in front of the most iconic picture spots in the valley (I'm reminded of the selfish people who linger in Delicate Arch in Arches National Park just as the sun is setting and dozens of people are trying to photograph the span without people mugging for cameras in the middle of it).
 Our last stop before leaving was in the meadow next to the Ahwahnee Hotel. The view is towards Happy Isles and Glacier Point. The day was every bit as peaceful as it looks, and the vast majority of people that I saw there were clearly loving the view. Everyone seemed just a bit quieter and introspective than the boisterous crowds I experience in the summertime.
 It was a beautiful day in one of my favorite places during my favorite times of the year!

Saturday, October 26, 2013

Duck Creates "Water Color" Art: Autumn in Yosemite Valley

You are welcome to call this my strangest blog post ever (and I've had plenty), but I was just captivated today. I live just two hours away from Yosemite Valley, and I visit every chance I get, and a bit of simple math tells me I've been in Yosemite around 80 times in the last quarter century. I never get tired of visiting, but I do have a standing rule of trying to discover something new and different every time I go. Sometimes it's a new mood, brought about by sky and weather conditions, sometimes it's a new place, and sometimes it is simply showing up with someone who has never been there before.

Today we found a new turnout and short trail that brought us to the south side of the Merced River across from El Capitan. The fall colors were indescribably beautiful, and the river is low and calm. As far as I know this is the first time I've caught El Capitan reflecting off the still, perfectly calm river. Except a duck spoiled it all.
The duck was just doing normal duck things, looking around for something good to eat, and she didn't seem to mind that I was watching. She would just sit for a few moments, sending ripples evenly in all directions, and other times she would swim forward, sending out bow shock ripples ahead.
With the vibrant colors of fall foliage, gray cliffs of granite, and the green of the conifers, the reflections on the rippling water took on the appearance of an impressionistic interpretation of reality.
Or, if you want, call it a kaleidoscopic vision. In any case, I thought the duck made some beautiful art out there on the Merced River. 
Mind you, the rest of the day was beautiful beyond description too. More pictures of the rest of our quick little journey will be coming soon!

In the meantime, enjoy, or ignore the quack-up of your host here at Geotripper!

The Volcano That Doesn't Exactly Look Like a Volcano: California's Lassen Peak

Lassen Peak is an odd one. Most people have a stereotypical view of what a volcano "should" look like, and to most people, Lassen doesn't fit the stereotype. Yes, it is an isolated peak from most angles, but where is the cone shape, and where is the crater on top?

We were on the last day of our late September field studies course through the Cascades of Northern California, and were having a look at the volcanic features of Lassen Volcanic National Park. In the previous post we took in a fascinating set of six plug domes, the Chaos Crags, and the debris avalanches that thundered down their flanks forming the Chaos Jumbles.

Like the Chaos Crags, Lassen Peak is a plug dome, a steep rubble-covered peak composed of dacite or rhyolite. It may be the largest plug dome in the world, rising about 2,000 feet above its base (most domes are half of that). It lacks the characteristic cone shape of stratovolcanoes because its lavas were so viscous upon emerging from the depths that they barely flowed at all, forming a steep pile of lava rather than relatively smooth slopes. As the lava cooled, it contracted and broke up, forming the talus slopes that coat most of the mountain.  A few rugged cliffs of solid dacite stick out here and there. The peak tops out at 10,457 feet, so it is often coated with snow.

Lassen Peak emerged during a series of eruptions about 28,000 years ago. The entire mountain probably developed in just a few years. Its shape was modified by latest episode of Pleistocene glaciations, but it was otherwise dormant for tens of thousands of years. Until 1914, that is...

In May of 1914 a steam explosion rocked the top of the mountain, producing a small crater on the summit. Over the next year at least 180 explosions blasted away at the summit, ultimately producing a 1,000 foot wide crater. The eruption made news across the country. Brave but foolhardy souls climbed to the summit to have a look, including several men who were standing at the summit on June 14th when B.F. Loomis made the famous images reproduced below (these are pictures I took of the displays in the Loomis Museum at Manzanita Lake).
One of the men, Lance Graham, was walloped by a rock in the shoulder and in the panicky moments that followed was left for dead near the top of the mountain. A rather lurid NY Times story described him as actually being dead, his arms cut off, a deep gash exposing his heart, and his body nearly torn in half; a later correction stated : "...he was reported to be dead, but the latest word is that he still is alive, although fatally injured". He apparently survived to live a long life (I recounted this story in one of my classes, and a surprised student piped up saying "Graham? He was my great grandfather!").

On May 19th of 1915, lava emerged from the volcano for the first time. The thick flow melted thick banks of snow and produced a major mudflow, or lahar, that traveled many miles down two valleys on the north flank of the mountain, destroying six ranch houses.

Source: National Park Service. Photograph by R.E. Stinson
The volcano was quiet for two days, and some may have thought the eruption was subsiding. It wasn't. On May 22nd, a huge explosion lifted ash 30,000 feet into the sky. A plume of hot ash swept down the north flank of the mountain, destroying the forest and all living things over an area of three square miles (these hot ash clouds are called pyroclastic flows or surges). This site is called the Devastated Area, and the demarcation between the old forest and the pyroclastic flow is still clear. The mountain has been quiet since 1917 (except for a puff or two of activity in 1921)

The eruption of Lassen Peak was for sixty years the only volcanic activity to take place in the lower 48 states, and as such was often the main topic of discussion in the volcanoes chapter of geology text books. It was a "nice" eruption in that it displayed many diverse phenomena (steam explosions, ash flows, lava flows, and mudflows), and didn't kill anybody (despite Lance Graham's near miss with mortality). Even though Mt. St. Helens stole all the attention, Lassen Volcanic National Park remains one of the best places I know of to learn about volcanism. And it is a beautiful place to visit.

More in the next post!

An excellent description of the 1914-17 eruption can be seen here:

Thursday, October 24, 2013

Chaos! The Jumbles and Crags of Lassen Volcanic National Park

Lassen Volcanic National Park is one of the lesser-known and less visited of the national parks in California. Many have heard of Lassen Peak, but the park is located in the northern reaches of the state relatively far from most population centers. It's a fascinating place, and if one is interested in volcanism, there are examples of practically every type of volcanic feature within the borders of the park. How many places in the world have shields, lava plateaus, stratovolcanoes, plug domes, cinder cones, and calderas, as well as active geothermal fields (fumaroles, boiling mudpots, and hot springs; everything except geysers, so Yellowstone can rest easy). The park is also noted for the recency of many of these features, with numerous cones and flows that are less than a few thousand years old (Lassen itself erupted from 1914-1917).

On our recent trip, we approached the park from the north, and the first sight we beheld was beautiful Reflection Lake. In the morning light it was serene and quiet, and it was strange to consider the violence that led to the lake's formation (along with nearby Manzanita Lake). The forest hides the hummocky surface of the landscape that surrounds the lake, but a short distance up the road, the origin of the lake becomes clear.
The Chaos Jumbles is the remains of a large debris avalanche that thundered down the slopes of  nearby Chaos Crags. The lack of soil and vegetation suggests that the avalanche deposits are not old (there are at least three of them), and indeed none of the trees on the slide date to more than three hundred years. The slide traveled on a cushion of compressed air, traveling for more than two miles and climbing some four hundred feet up the slope on the far side of the valley. It blocked several streams, ultimately forming the beautiful lakes.
The rocks that make up the slide are quite interesting as well. They are volcanic, but not the black basaltic rock that people associate with lava flows and volcanoes. It is a pinkish brown volcanic rock called dacite. Dacite is intermediate in composition between rhyolite and andesite, containing the minerals quartz, plagioclase, hornblende and biotite. The volcanic rock also contains enclaves of a darker volcanic rock, an andesitic basalt that shows that two different magma chambers were comingling and mixing. The mixing probably was a factor in the eruptions of the dacite.
An aerial shot of the Lassen vicinity shows the Chaos Crags in sharp outline. They are the barren snow-free peaks to the left of the main cone of Lassen Peak (the Crags lie north of Lassen; the picture is oriented towards the southeast). Given the dense thick forest that surrounds the volcanoes and the barren nature of the Crags, they have to be exceedingly young, and dating indeed places their age at about 1,100 years before the present. Six individual domes were erupted during a period of about 60 years.

The Chaos Crags are excellent examples of plug domes, short steep cones produced by highly viscous lava flows. The lava emerged like toothpaste from the ground, and as it cooled, the surface of the lava contracted, breaking up and forming huge debris piles on the margins of the cone.

The six domes have been creatively named A, B, C, D, E, and F. Domes E and F can be seen in the picture below, while Dome D dominates the bottom picture.

In any other setting, the Chaos Crags would be the central focus of a volcanic park, but the much taller peak of Lassen stands less than two miles away, so they tend to be somewhat ignored. That's too bad because there are few better examples of plug domes to be found anywhere, and the youthfulness of the Jumbles suggests continuing geologic activity. A stop among the chaos of the Crags and Jumbles is a great introduction to the geology of Lassen Volcanic National Park!