Vagabonding on Dangerous Ground: Playing Hide and Seek with a Sleeping Monster

Mt. Baker and Boulder Creek upstream of Baker Lake Reservoir

There's something about traveling through the Pacific Northwest that I may never become accustomed too: the deep, deep forests. As a child in the scouts, living in arid Southern California, I was pretty good at orienteering with a compass and map, but that was predicated on the fact that I could see the mountains around me. That would have been tougher if I had grown up in a rainforest. Every view is of a tree!

And so the struggle to actually see Mt. Baker in the Cascade Range. We had actually traveled around three sides of the mountain in the last two days, but I never got much of a glimpse, either because of the deep forest, or, you know, having to pilot the car without plowing into a tree or a deer. We finally got serious about the effort by detouring onto Baker River Road as we left North Cascades National Park. The road would take us within six miles of the summit as the crow flies. If we couldn't see it from there, we didn't deserve to see it.

This web series was entitled Vagabonding on Dangerous Ground primarily because we happened to be following the coastal parts of the Cascadia Subduction Zone which had become newsworthy over the summer because of a New Yorker article detailing the probable damage from an expect magnitude 9 earthquake offshore. Shaking, tsunamis, landslides, power disruptions and many other frightening events were part of the article. Kind of lost in the whole media affair were the sleeping giants that have always been a visceral threat to those who live in the region: the volcanoes.

In Cascadia the subducting slab of cold oceanic crust and underlying solid mantle material (the lithosphere) are driven into the much hotter asthenosphere, a "mushy" layer in the mantle that is partly molten. The interaction of the slab, water from the oceans, and the hot mantle rocks causes melting of some of the continental crust, forming magma that rises through the crust as a series of plutons. When they cool before reaching the surface, they will form visibly crystalline rocks like granite or diorite. When they reach the surface in a molten state, magma mayhem ensues.

The molten flows of lava that Hollywood seems to love the best are often the least serious problem during an eruption of a Cascade volcano, if they occur at all. More often any lava flows will melt prodigious amounts of snow and ice, producing volcanic mudflows (lahars) that can flow for tens of miles, causing damage at great distances from cone. In ancient times lahars could strike without warning from an eruption that couldn't be seen from within distant downstream canyons.

Some lahars aren't even associated with volcanic eruptions. They can be triggered by landslides on the upper reaches of the steep cones, or by unusually high amounts of glacial melting (water trapped under the glacier may burst out all at once). Mt. Baker has the most snow and ice of any Cascades volcano except Mt. Rainier (and that's a big except, as Rainier has about 50% of all the ice in the lower 48 states). So lahars are the big danger from Mt. Baker.

The other dangers result from explosive eruptions that pulverize the magma and other rocks around the summit of the volcano. The fine dust that results is called volcanic ash. The ash can be so hot close to the volcano that it can be incandescent. Anyone or anything caught in the fast moving ash flows is doomed, plain and simple. An ash eruption hit the Martinique town of St. Pierre in 1902 and killed all but two of the town's 30,000 inhabitants. These hot ash flows are called pyroclastic flows, or nuée ardente, French for "fiery cloud". The good news in the case of Mt. Baker is that relatively few developments are close enough to the peak to be threatened. But there are some.

Hazard areas in and around Mt. Baker in northern Washington

We found great views of the volcano from the dam at Baker Lake, and from Boulder Creek. Boulder Creek also provided a nice view of some lahar deposits as well, possibly from events in 1843 or 1891.

Mt. Baker is one of the youngest of the Cascade volcanoes, having formed mostly in just the last 30,000 years. The last major eruptions took place around 6,600 years ago when large lahars swept down creek valley accompanied soon after by ash eruptions. The 1843 eruption was caused by a hydrovolcanic explosion (groundwater flashing to steam). That event left behind Sherman Crater. In 1975, there was a vast increase in the amount of thermal energy around the summit of the mountain, raising fears of an eruption. The heat subsided somewhat, and everyone forgot about Mt. Baker when Mt. St. Helens exploded just five years later.

Lahar deposits at Boulder Creek near Mt. Baker

We were seriously on the homeward path now. No meandering highways along beautiful coastlines for us anymore. Interstate 5 was going to be our pathway now as we pushed south. But the Cascadia Subduction Zone had one more beautiful surprise for us. We'll wrap up our journey in the final post soon!

Driving Through the Most Dangerous Plate Boundary in the World: A Landscape Buried in Hot Mud, and a 6-foot Long Saber-tooth Salmon

Mt. Shasta is a big mountain. A really big mountain. Reaching an elevation of 14,179 ft (4,322 m), and rising nearly 10,000 ft. (~3,000 m) above the surrounding terrain, it has a volume of around 100 cubic miles. As such, it is the biggest volcano in the Cascades volcanic arc, and probably is on the short list of largest stratovolcanoes in the world (shield volcanoes like those of the Hawaiian Islands have a different origin and are much, much larger). The volcano is the surface manifestation of the sinking of the Pacific lithospheric plate beneath the North American continent along the Cascadia Subduction Zone. As the plate sinks deeper, superheated water is liberated, which lowers the melting point of the deep rocks, forming magma chambers that sometimes erupt at the surface.

The thing is, one would think that this massive edifice would be made of lava and volcanic ash, but a large percentage of the volcano is actually composed of...mud. Simple mud. Well, more properly, mudflow deposits, or lahars, as they are called by geologists. This isn't the kind of mud you find on the bottom of a lake or the sea. It was mud born of violence. The mud includes massive boulders, showing that the formation of the lahars involved the rapid melting of snow and ice during violent eruptions. The mixing of water, ash and rock fragments forms a slurry that moves quickly down the flanks of the volcano. To humans, they are dangerous. A lahar in Colombia in 1985 killed around 23,000 people in a matter of minutes.

On our journey through the most dangerous plate boundary in the world, we've explored the accretionary wedge and forearc basin of the massive subduction zone that once existed off the California coast, and now we've reached the base of the most visible part of the system: the magmatic (or volcanic) arc . The arc is extinct today in this part of California, but one is still active in the Cascades of Northern California and the Pacific Northwest.

Driving through the foothills of the Sierra Nevada in places like Knight's Ferry or LaGrange, just north of the Yosemite National Park region, it's hard to visualize the violent past of this landscape. The gentle slopes belie the intensity of the floods and flows that carried the boulders for forty or fifty miles from the volcanic centers that once existed near the crest around Sonora Pass and the Dardanelles. The rocks are called the Mehrten Formation, and they were deposited around 5 to 7 million years ago, when the subduction zone was still active at this latitude. Similar mudflow deposits cover much of the northern Sierra Nevada.

Of course, the volcanoes weren't always erupting. Decades or centuries may have passed between eruptions, and the tattered ecosystem would recover. Petrified wood has been found in the formation, and fossils of horses, camels, and other animals that lived on the river floodplains emerging from the mountains above. A few years ago I became aware of some of the most unique fossil species to be discovered in the formation, gigantic tortoises, and six-foot-long salmon...with fangs! The Sabertooth Salmon (Oncorhynchus rastrosus) once swam the ancestral Stanislaus and Tuolumne Rivers, right here in my own back yard. That's almost as cool as living in a place that once had Mosasaurs (oh yeah, they lived here too).

A former student of Modesto Junior College (and current geology major at CSU Stanislaus), Jake Biewer, is working this summer on a new exhibit at the Great Valley Museum highlighting his research on the Sabertooth Salmon and the large tortoises of the Mehrten Formation. I'm looking forward to seeing the results!

In our next post, we'll discover what it's like to be living beneath the volcano. In the meantime, check out this video of a lahar at Mt. Shasta.

Driving Through the Most Dangerous Plate Boundary in the World: A Gentle Landscape Belies a Fiery Past

As we leave the Great Valley behind on our journey through the most dangerous plate boundary in the world, we finally enter the world of the Sierra Nevada. Many may think of Yosemite Valley or Lake Tahoe when the Sierras are mentioned, but the mountains rise modestly from the west side. The transition from the flat Great Valley to the gentle rolling terrain of the Sierra Nevada is not always obvious. Because most of my Sierra journeys begin there, we'll start in the central part of the range, the drainages of the Tuolumne, Merced, and Stanislaus Rivers. The picture below is the new bridge over the Tuolumne River near Old Basso Bridge upstream of Turlock Lake State Recreational Area.

This quiet gentle landscape belies a violent past in several ways. The initial rock outcrops along the rivers look sedimentary, given that they are layered and are composed of gravel, sand and silt, but the origin of some of these rocks was in fire. They are volcanic. Secondly, the lowermost rock layer found here contained gold, and miners ripped into these rocks with a ferocity that would humble today's heavy equipment operators. Thirdly, the rocks underlying these sediments record the intense deformation related to terrane collisions in an earlier time, when the Ancestral Sierra Nevada was forming.

The Sierra Nevada begins as prairie, or near the rivers, forests of cottonwood, sycamore, oak and the occasional Gray Pine. It's dry country, a far cry from the cool pine forests and alpine peaks that people usually associate with the Sierra Nevada. One can choose to follow the high-speed roads like Highway 108 out of Oakdale, or Highway 140 out of Merced, but I suggest some of the quieter avenues, like Lake Road or Highway 132. There are ranch roads that provide an even more serene journey through the foothills. The picture below is from Warnerville and Willms Roads east of Oakdale.

The basal sedimentary rock is called the Ione formation. The gravels, sands and clays of the Ione were deposited in a distinctly different environment than we see today. The sand was deposited along a beach strand, the clays (and associated low-grade coal deposits) in coastal estuaries and swamps, while the gravels settled in large rivers flowing into the coastal delta complex. Fossils in the Ione indicate tropical conditions. The Sierra of 40-50 million years ago was a coastal jungle, not unlike the coast of the Yucatan Peninsula of Mexico today!

Things changed around 25 million years ago. The climate cooled, the sea retreated to the west, and intense rhyolite eruptions began from calderas off to the east, near the present-day Sierra Crest, and farther away in central Nevada. These eruptions produced not lava, but volcanic ash, the pulverized remains of rock that exploded rather than flowed. These eruptions are the most violent known, killing all life over hundreds or thousands of square miles. The Sierra Nevada, a mountain range that had been laid low by erosion, was stirring again. The mountains were about to rise again...

Next up: mud. Lots and lots of mud...

Northern Convergence: America's Most Dangerous Volcano, and the End of the Journey

Northern Convergence as a name for this blog series was all about the role of a convergent plate boundary in the production of the scenery of the Pacific Northwest. The compressional forces that developed as the Pacific/Farallon/Juan de Fuca plate was stuffed under the North American continent formed range after range of complexly folded and faulted mountains hundreds of miles inland.

Perhaps the most vivid effect of plate convergence is the formation of a magmatic arc, a chain of inland volcanoes and underlying magma chambers. The oceanic lithosphere carries rock and water deep into the underlying asthenosphere where the rocks are heated, and the water liberated. The water has the effect of lowering the melting point of the mantle rock and plumes of molten magma form, which start moving upwards through the continental crust. Sometimes basaltic or andesitic magmas reach the surface. In other instances, the hot magma melts some of the continental granite, forming dacite or rhyolite.

Mt. Adams from Sunrise Ridge

Volcanism is one of the intense and spectacular geologic processes one could ever hope to witness (or avoid, if you not geologically-minded, or sane). Volcanoes are capable of horrific destruction and disaster, but they also provide rich fertile soils and incredible scenery. We had now been on the road for nearly two weeks, and an important early site for our investigations was to be Mt. Garibaldi and the Black Tusk, two of the northernmost Cascade volcanoes. As I wrote previously, rain and clouds obscured our views that day, and all we ended up seeing were some old lava flows (and, it should be said, some wonderful waterfalls).

Not a volcanic eruption, but instead a wildfire. Couldn't help imagining, though.

As we drove west on our final day, volcanism loomed. We would be passing through Mt. Rainier National Park, and it is hard to think of any mountain in the world that dominates the surrounding landscape the way Rainier does (Kilaminjaro comes to mind, or Mauna Loa in Hawaii, but few others). In stark contrast to our earlier visit at Garibaldi, the skies were crystal clear and sunny.

Mt. Rainier from the west

Rainier rises to an elevation of 14,411 ft (4,392 m), just a bit short of being the highest peak in the lower 48 states, but certainly the highest in the Cascades (only Shasta comes anywhere close at 14,179 feet). Glacial erosion has ripped away hundreds of feet of rock from the summit area, so at one time it was almost surely the tallest mountain in the lower 48 (one more contender though could be the San Francisco Peaks in Arizona, another stratovolcano missing thousands of feet from the summit).

Rainier from the air

For all of its grandeur, Rainier is an incredibly dangerous mountain. It contains roughly half of all the glacial ice to be found in the lower 48 states, around a cubic mile. That much ice and a tendency to have eruptions every few hundred years is a frightening combination. Many people think (perhaps influenced by bad Hollywood movies that involve volcanoes) that lava flows are the greatest hazard from volcanoes. They are not; lava flows would hardly be expected to get off the mountain massif itself. Andesite is just too sticky to flow far before congealing.

Source: Mount Rainier - Living Safely With a Volcano in Your Backyard by Carolyn L. Driedger and William E. Scott, USGS -- from USGS fact sheet 2008-3062

The ice is another matter. A modest eruption of ash or lava could melt a vast amount of ice, mixing with the ash to form a fast-moving mudflow called a lahar. Over the history of the volcano lahars have had the greatest reach, extending as far as the Puget Sound. The cities of Tacoma, Puyallup, Sumner and others are built on lahar deposits from Rainier (see above). Tens of thousands of people along the drainages below Rainier will have a few tens of minutes to evacuate in the event of a major mudflow. For all its beauty, the mountain is a ticking time bomb. It's also probably one of the most carefully monitored mountains on the planet. I don't doubt that the slightest hint of activity will bring a flurry of evacuations.

Rainier from the air in 2007

We spent a few hours on Sunrise Ridge, but our time was limited. We had nearly completed our journey and some of our people needed to catch flights at SeaTac. We headed down the hill towards Puget Sound. We had seen many wonders on the roads that took us across the Olympic Peninsula, the ferry to Vancouver Island, a rainsoaked drive through the Sea to the Sky Highway, explorations of Banff and Yoho National Park, a sojourn among the ghosts of dinosaurs on the High Plains, and a drive home through the Rocky Mountains and the Columbia Plateau. I had gotten to know an extraordinary group of people, and a small corner of a most extraordinary country, Canada.

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: http://www.nps.gov/lavo/naturescience/upload/eruptions_of_lassen_peak.pdf

Picture of the Day - The Airliner Chronicles Part 4

Mt. Hood, in northern Oregon, is one of the most beautiful and symmetrical stratovolcanoes in the Cascades. At 11,249 ft. (3,429 m), it is the tallest mountain in Oregon. It is also considered to be one of those most likely to erupt in the next few decades or centuries, with nearby Portland at risk for lahars and ash falls. As noted in previous posts, these volcano pictures resulted from a flight to Seattle on an extraordinarily clear day in 2003.

Picture of the Day - The Airliner Chronicles Part 2

Some obvious choices come first...volcanoes are spectacular from above. I had an extraordinary flight to and from Seattle, when the skies were clear and cloudless, and the route took us alongside nearly all of the Cascades volcanoes (those pictures are forthcoming). The return flight, which started after sunset, did not seem to offer many possibilities for photography, but the long twilight caused Mt. Rainier to shine with a blue glow that was ghostly and hypnotic. Rainier is the tallest Cascade volcano, and has the longest glaciers in the lower 48 states. It is not considered to be much of a risk for explosive eruptions, but even a small non-explosive eruption could produce massive lahars (volcanic mudflows), as melting glacial ice mixes with ash and debris. Several large urban areas at the south end of Puget Sound are at risk.