Travels in Cascadia: Threading the Needle on Hurricane Ridge

Leading a field studies trip is a stress-filled enterprise. There are the big things to worry about: auto accidents, injuries, conflicts with law enforcement, lost reservations, and those sorts of things. But those thankfully don't happen much. But weather does happen, and field studies trips tend to be tightly scripted affairs with not much room for weather-related complications. Yet they happen, especially on trips in the Pacific Northwest. We've had trips where we had just the one chance to see Mt. St. Helens, and it was completely fogged in. There was the one chance to see the Sea to Sky Highway in British Columbia, and it was raining the entire way. We've missed a lot.

This year was going to be different. We worked some flexibility into the schedule, spending two nights each at most of our localities, giving us the chance to postpone a particular plan for a day to allow the weather to clear up. But on our second day out, I was worried. Ever since the longest ten-day forecast, a storm was brewing out in the Pacific Ocean, one that was arriving in waves over several days. We had given ourselves two days on the Olympic Peninsula, and rain was falling on Hurricane Ridge the first day, so we elected to go to Neah Bay and Cape Flattery instead. But that left us just one more chance to have a clear view at Hurricane Ridge in Olympic National Park. The sunrise (above) was not promising. According to the forecast, we would have a brief window of maybe three or four hours before the storm closed in, but we drove through light showers on the road up to the ridge.

My concern grew as we continued up the road, rising from sea level to over 5,000 feet. The far ridges would appear for a moment and then become obscured, and I didn't know until we reached the top ridge if we would actually see anything...

… but we did! And no matter how many times I've been on Hurricane Ridge, nothing quite prepares me for the view from the end of the paved road. It is simply astonishing. As we emerged from the vehicles I felt the stress falling away, like dropping a particularly heavy load from my shoulders. We gathered the group and said a few words about the geology. We would save the longer presentations for later in the day down the hill. With an impending storm, I didn't want our students to miss any of the dramatic scenery. And it is dramatic.

The Olympic Mountains rise from sea level to nearly 8,000 feet and are extremely rugged. They capture prodigious amounts of rain and snow on the western flanks, so much so that temperate rainforests coat the western slopes. It was a nightmare for geologists who were trying to unravel the geologic history.

The mountains exist because of subduction. For most of 200 million years a convergent boundary has been active in the region, as the crust of the Pacific Ocean basin has been sinking against the edge of the North American Continent. In some places, like California, the subduction zone has been replaced by a transform boundary (the San Andreas fault). But in Northern California, Oregon, Washington, and part of British Columbia, the subduction zone is still active, still producing earthquakes, and still raising mountains. It's called the Cascadia Subduction Zone (from hence comes the name of this series).

Source: Geological Society of America

In a "normal" subduction zone, there are four parts: the trench, an accretionary wedge, a forearc basin, and a magmatic arc. The trench is the deepest part of the ocean floor where the oceanic crust sinks back into the mantle. The accretionary wedge is a collection of seafloor sediments and crust that has been scraped off the subducting plate and added to the edge of the continent. The forearc basin is a shallow sea that may develop inland of the accretionary wedge (California's Great Valley originated in this fashion). The magmatic arc is a system of volcanoes and intrusive plutons resulting from the melting of rocks in the lower crust and upper mantle above the descending slab (water released from the slab lowers the melting point of the rock, leading to the formation of the molten rock).

Looking at the thickly forested slopes below Hurricane Ridge, I cannot envy the geologists who originally mapped the Olympic Mountains. Simply finding an exposure of rock must have been challenging at times. What these geologists did was to take the rare rock exposures and extrapolate them into a semi-coherent map that reveals the structure of the Olympic Mountains. They did the equivalent of taking a few pieces of a jigsaw puzzle, putting them in the right location relative to the others, and then drawing in the remainder of the puzzle from scratch. I've been way too spoiled by the naked rock exposures of places like Death Valley and the Mojave Desert!

The geologic map reveals the basic structure of the Olympics. A "horseshoe" of basalt and sedimentary rocks (the Peripheral Rocks, or Crescent Formation) partially surrounds the "Core Rocks", an assemblage of lightly metamorphosed sandstone and shale layers. The Core Rocks are characteristic of the types of deposits that form from underwater landslides ("turbidity currents") within the trench and accretionary wedge of a subduction zone. The fact that these rocks are now thousands of feet above sea level is the interesting conundrum. Accretionary wedges are generally below sea level, or exist as small islands. They can be pushed higher. For instance, the rocks of the Cascadia accretionary wedge are exposed in the Coast Ranges of  Washington, Oregon and California, but nowhere are the exposures as spectacular as the Olympic Mountains.

Convergent boundaries can be exceedingly complex places. Bits and pieces of continents and island arcs may randomly arrive at the subduction zone, mucking up the subduction process the way too many sheets of paper at once can muck up a paper-shredder. In the case of the Olympics, there was a mass of land north (Vancouver Island) and an accreted terrane to the south (the North Cascades), and a bend in the subduction zone itself. In essence, too much material was being stuffed into the subduction zone, so the excess material went the only way it could, which was up. The mountains have been rising for around 15 million years. They would be higher, but the incredible amount of precipitation tears the mountains down at a roughly equivalent rate.

Pillow basalt from the subducted oceanic crust is exposed along the Hurricane Ridge Road and along trails near the viewpoint. When we went down the road later on, we found that a small rockfall had dumped some of the pillows onto our highway. So, as it turned out, we managed to miss having rocks fall on our vans, i.e., one of the hazards I mentioned at the start of the post!

We could easily observe the glaciers that scour the upper reaches of the mountains. Glaciers technically shouldn't exist here. Although we were at a high enough latitude, the nearby Pacific Ocean moderates the climate, keeping things warmer than they would otherwise be (the Olympics are at the same latitude as Great Falls, Montana, or St. Paul, Minnesota). But temperature isn't the only factor in glacier development. The sheer amount of snowfall in combination with temperatures that are just cold enough allows glaciers to exist at these unusually low elevations.

We had a good introduction to the basic features of alpine glaciation as we gazed across the valley to Mt. Olympus. There were horns, aretes, and cirques as well. Glaciers were going to be a big part of the story of British Columbia, and Hurricane Ridge provided a spectacular setting for the first discussion of how they worked.

It was nearly noon and the storm clouds were building. We were rained on as we descended back down to the lowlands. It was time to prepare for the ferry ride across the Strait of Juan de Fuca to Vancouver Island.

Travels in Cascadia: The Southern Sentinel, Mt. Shasta

Long ago in the mists of time, the god Skell, the spirit of the Above-World descended from the heavens and alit on the summit of Mt. Shasta. Eventually Skell waged a fierce battle with the god of the Below-World, Llao, who resided in Mazama, a high mountain to the north. There was much fire and ash, and the skies grew dark. In the end Skell prevailed and the body of Llao was cast back into the underworld, taking a good portion of Mazama with him. The tears of his followers filled the gaping hole, becoming what is today known as Crater Lake.

The collapse of Mt. Mazama was an actual event around 7,000 years ago and it was witnessed and remembered by the inhabitants of the region who told the story above. Large volcanoes loom large in the consciousness of people, as they possess great power and have the potential for great destruction. Mt. Shasta is no exception, and even today a multitude of people tell stories of Lemurians, Atlanteans, and aliens who all seem to have an abode in the mountain somewhere.

Geologists are story-tellers too, although they tend not to invoke gods as a reason for the mountain's activity. They instead look for the natural laws of the Universe to understand how volcanoes work (in a sense those natural laws are the gods of the sciences). It may be that hundreds of years from now, our stories will be seen as quaint myths, but like all societies and cultures, we understand things through the prisms of our technology, mutual experiences, and observations.

I've always found it fascinating the way humans interpret their world, and I've devoted my life to teaching the scientific view. But I come from a family and a society that has not been grounded in the landscape that it inhabits. It is a society of immigrants from all over the world who invaded a "new land" that had in fact been inhabited for thousands and thousands of years before being conquered. Understanding these cultures enriches our understanding of the land, and so I find myself being enthralled by the sciences of anthropology and archaeology. Ultimately I joined forces with the professors of anthropology at Modesto Junior College to put together a series of field courses that teach both the geology and the anthropology of the landscape. We've been to Italy and Switzerland, Hawaii, and all over the Southwestern United States. Most recently though, we explored British Columbia and the northern parts of Washington state. This new series I'm writing will explain my impressions of the trip that we took with 15 students, my fellow professor of anthropology, and Mrs. Geotripper. The term "Cascadia" refers to the Cascadia subduction zone, the huge gash in the Earth's crust that dominates the geology of the region.

Our students didn't actually see Mount Shasta, unless they saw it out the plane window. They all met us at SeaTac airport, but we had reasons to drive from California to Washington. Mt. Shasta is the foremost landmark in Northern California. It is at the southern end of the Cascadia subduction zone, and is considered potentially active (Lassen Peak is even further south, but we only had a brief view of it). It is a classed as a stratovolcano (or composite cone) and is composed mostly of andesite, a gray-colored intermediate silica volcanic rock. It has had eruptions roughly every 600 years over the last 10,000 years, with the most recent event probably in 1786. At 14,179 feet, it is the second highest Cascade volcano, but in volume it is the largest. There are five major glaciers around the summit, including Whitney Glacier, which at two miles is the longest glacier in California.

The volcano is actually a composite of four different cones of different ages: Sargent's Ridge, Misery Hill, Shastina, and Hotlum Cone. There was an even earlier version of Shasta dating to 600,000 years ago, but around 300,000 years ago the summit collapsed to form a gargantuan debris slide that traveled 28 miles north of the volcano, almost to Yreka. The lumpy hummocky surface visible around the Interstate 5 rest area near Weed is part of the ancient mass wasting event.

Shasta is visible from more than a hundred miles away, but as we continued north, the mountain receded from view. We got to Portland, Oregon, just in time to catch a few sights before the sun set. That story will be in the next post!

A Look Back at Ten Years of Geotripping: Vagabonding on Dangerous Ground, an Exploration of Cascadia

In 2015 I wrote a blog series about driving through the "Most Dangerous Plate Boundary" in the world, but it was actually about driving through a fossil subduction zone that is exposed in the Coast Ranges, Great Valley and Sierra Nevada of Central California. In the summer of 2015, Mrs. Geotripper and I took a long journey along the entire length of a real "dangerous plate boundary", the Cascadia subduction zone, that extends from Northern California to British Columbia. The trip coincided with a media explosion over the very real possibility of a magnitude 9 earthquake along the Pacific Northwest coastline. This resulted in another blog series, Vagabonding on Dangerous Ground. Here is a compilation of the journey...

This was posted on September 13, 2015...

I've finished a new blog series on our exploration of the Cascadia Subduction Zone, so I've compiled all the posts in chronological order so you can get the story the correct sequence. Thanks for all the nice comments, responses, and corrections! Click on the orange titles for the post.

On the Road in the Pacific Northwest: The introduction and overview of the new blog series.

Following the Cascadia Subduction Zone on Highway 101: This post provided the geological background for understanding the hazards of living in the lands influenced by the Cascadia Subduction Zone.

In This Land of the Sasquatch There are Ancient Giants: The first leg of our journey took us through the range of the California Redwoods and the land of black bears that look suspiciously like walking ape-people.

The End is Coming (of the Cascadia Subduction Zone): The end of Cascadia is a slow process, but the zone is disappearing slowly, being replaced by the San Andreas fault. It's also a look at one of the loneliest beaches in California.

A Geologist Walks Onto a Bar in Cascadia: Exploring the unique baymouth bars along the Humboldt county coast.

Northern California's Tsunami Central: Crescent City has a tragic history of tsunamis, especially the one in 1964 that took a dozen lives and destroyed the marina and downtown areas.

This "Dismal Forest Prison" and other problems exploring the Northwest: The Pacific Northwest was particularly difficult to explore and map, at least if you weren't part of the indigenous culture. Here are some accounts of the discovery of Humboldt Bay by land.

Into the Land of Sand, and Exploding Whales: Between Coos Bay and Florence, Oregon, is the longest stretch of sand beaches and dunes in the Pacific Northwest. Yeah, and the whale thing...

Into the Realm of the Devil (and Sea Lions): There are a lot of things named for the devil on the Oregon coast for some reason. And some incredible sea caves occupied by sea lions.

Putting on a Happy Face at Dismal Nitch and Cape Disappointment: We reach the mouth of the Columbia River, where Lewis and Clark reached their goal. It's undergone a great many changes over the years.

Into the Rainforest, Seeing Something Strange...Rain: We explore the Hoh Rainforest in Olympic National Park for the first time, and encounter something strange, at least this year: rain. There was also a fire burning in the rainforest. That's not normal.

The Diverse Landscapes of Olympic National Park: Olympic is one of the most diverse of our national parks, with alpine glaciers, rainforests, and coastlines. It's spectacular.

The Salish Sea and the Strait of Juan de Fuca: Glaciers and tectonics combined to form a seaway east of Vancouver Island and the Olympic Peninsula. It's a unique ecosystem quite distinct from the Pacific Ocean just a few miles away.

Stone Rings, Glaciers, and "Dinosaurs" on the Coast of the Salish Sea: Desecrated burial mounds, avian dinosaurs, and glacial landscapes. Victoria on Vancouver is both a beautiful city and a fascinating place to explore.

Exploring North America's Southernmost Fjord: We take the ferry to the mainland, making landfall inside of the southernmost glacial fjord in North America, Howe Sound in British Columbia (defined here as on the mainland, but connected to the ocean; opinions differ!).

Landing Place of the Thunderbird and the Grimy One, the Volcanoes of British Columbia: Black Tusk and Mt. Garibaldi two of the northernmost volcanoes in the Cascade Range. I missed them last year in the rain, but saw them this time.

Controversial Stone People, Fire and Ice, and an Olympic Legacy: We made it to Whistler and the home of the 2010 Winter Olympics. The stone people were controversial, but the scenery was not. It was spectacular.

Seeing Volcanoes from the Inside Out at Siám' Smánit (Stawamus Chief): Glaciers and granite! Stawamus Chief is a dramatic granitic dome rising high above the end of Howe Sound. It was once the magma chamber of a volcano.

Our Tour of the Greatest National Park I Never Once Set Foot In: North Cascades National Park is a true primeval wilderness. No roads penetrate the park boundaries. But what incredible scenery!

The Geology that Explains Why North Cascades is a Park Divided: The Skagit River may be the most altered water course in the Pacific Northwest, but it provides 20% of Seattle's electricity. It splits a national park in two.

What's East of North (Cascades), A Brief Explore: North Cascades doesn't have all the scenery; the lands to the east are rather spectacular too, and offer some great geology.

Playing Hide and Seek with a Sleeping Monster: Mt. Baker is not the most active volcano in the Cascade Range, but it is capable of great mayhem. It even looked for awhile like it might blow back in 1975.


Danger Follows Us Home (As it does all of us): A Mt. Shasta drive-by (photo) shooting, and a wrap-up of the series. Danger is always with us no matter where we are. It's not to be feared, but respected and prepared for.

Vagabonding on Dangerous Ground: A Compendium of Posts

I've finished a new blog series on our exploration of the Cascadia Subduction Zone, so I've compiled all the posts in chronological order so you can get the story the correct sequence. Thanks for all the nice comments, responses, and corrections! Click on the gray titles for the post.

On the Road in the Pacific Northwest: The introduction and overview of the new blog series.

Following the Cascadia Subduction Zone on Highway 101: This post provided the geological background for understanding the hazards of living in the lands influenced by the Cascadia Subduction Zone.

In This Land of the Sasquatch There are Ancient Giants: The first leg of our journey took us through the range of the California Redwoods and the land of black bears that look suspiciously like walking ape-people.

The End is Coming (of the Cascadia Subduction Zone): The end of Cascadia is a slow process, but the zone is disappearing slowly, being replaced by the San Andreas fault. It's also a look at one of the loneliest beaches in California.

A Geologist Walks Onto a Bar in Cascadia: Exploring the unique baymouth bars along the Humboldt county coast.

Northern California's Tsunami Central: Crescent City has a tragic history of tsunamis, especially the one in 1964 that took a dozen lives and destroyed the marina and downtown areas.

This "Dismal Forest Prison" and other problems exploring the Northwest: The Pacific Northwest was particularly difficult to explore and map, at least if you weren't part of the indigenous culture. Here are some accounts of the discovery of Humboldt Bay by land.

Into the Land of Sand, and Exploding Whales: Between Coos Bay and Florence, Oregon, is the longest stretch of sand beaches and dunes in the Pacific Northwest. Yeah, and the whale thing...

Into the Realm of the Devil (and Sea Lions): There are a lot of things named for the devil on the Oregon coast for some reason. And some incredible sea caves occupied by sea lions.

Putting on a Happy Face at Dismal Nitch and Cape Disappointment: We reach the mouth of the Columbia River, where Lewis and Clark reached their goal. It's undergone a great many changes over the years.

Into the Rainforest, Seeing Something Strange...Rain: We explore the Hoh Rainforest in Olympic National Park for the first time, and encounter something strange, at least this year: rain. There was also a fire burning in the rainforest. That's not normal.

The Diverse Landscapes of Olympic National Park: Olympic is one of the most diverse of our national parks, with alpine glaciers, rainforests, and coastlines. It's spectacular.

The Salish Sea and the Strait of Juan de Fuca: Glaciers and tectonics combined to form a seaway east of Vancouver Island and the Olympic Peninsula. It's a unique ecosystem quite distinct from the Pacific Ocean just a few miles away.

Stone Rings, Glaciers, and "Dinosaurs" on the Coast of the Salish Sea: Desecrated burial mounds, avian dinosaurs, and glacial landscapes. Victoria on Vancouver is both a beautiful city and a fascinating place to explore.

Exploring North America's Southernmost Fjord: We take the ferry to the mainland, making landfall inside of the southernmost glacial fjord in North America, Howe Sound in British Columbia (defined here as on the mainland, but connected to the ocean; opinions differ!).

Landing Place of the Thunderbird and the Grimy One, the Volcanoes of British Columbia: Black Tusk and Mt. Garibaldi two of the northernmost volcanoes in the Cascade Range. I missed them last year in the rain, but saw them this time.

Controversial Stone People, Fire and Ice, and an Olympic Legacy: We made it to Whistler and the home of the 2010 Winter Olympics. The stone people were controversial, but the scenery was not. It was spectacular.

Seeing Volcanoes from the Inside Out at Siám' Smánit (Stawamus Chief): Glaciers and granite! Stawamus Chief is a dramatic granitic dome rising high above the end of Howe Sound. It was once the magma chamber of a volcano.

Our Tour of the Greatest National Park I Never Once Set Foot In: North Cascades National Park is a true primeval wilderness. No roads penetrate the park boundaries. But what incredible scenery!

The Geology that Explains Why North Cascades is a Park Divided: The Skagit River may be the most altered water course in the Pacific Northwest, but it provides 20% of Seattle's electricity. It splits a national park in two.

What's East of North (Cascades), A Brief Explore: North Cascades doesn't have all the scenery; the lands to the east are rather spectacular too, and offer some great geology.

Playing Hide and Seek with a Sleeping Monster: Mt. Baker is not the most active volcano in the Cascade Range, but it is capable of great mayhem. It even looked for awhile like it might blow back in 1975.


Danger Follows Us Home (As it does all of us): A Mt. Shasta drive-by (photo) shooting, and a wrap-up of the series. Danger is always with us no matter where we are. It's not to be feared, but respected and prepared for.

Vagabonding on Dangerous Ground: Danger Follows Us Home (As it does all of us)

Mt. St. Helens from Silver Lake

We have finally reached the last few days of our meandering journey through the lands influenced by the Cascadia Subduction Zone. We spent several weeks out there, checking out the landscapes threatened by a possible magnitude nine earthquake. Although the hazard has been recognized for quite a few years, there was a media storm over the summer that brought the dangers into focus for the people living in the coastal zones of the Pacific Northwest. We were on our vacation anyway, traveling up the coast, but our search for beautiful scenery became an exploration of geological landscapes threatened by earthquakes, landslides, tsunamis and floods.

After many days in Oregon, Washington and British Columbia, we were on the homeward road, traveling hundreds of miles a day, knowing that issues at home needed attention. It didn't leave much time to investigate the other danger facing those in the northwest: volcanic activity. We got to see Mt. Baker for the first time, and Mt. Garibaldi, but Mt. Rainier and Mt. St. Helens were hidden in the clouds (we had a brief view of St. Helens from Silver Lake; see the first picture). Mt. Hood, the Three Sisters, Crater Lake, and all the other Cascade volcanoes were hidden behind the forested ridges. We couldn't see them from the freeway, and we had no time for detours.

But then we crossed back into California, forded the Klamath River, and surmounted a ridge where a gigantic mountain came into view. It was Mt. Shasta (14,179 feet / 4,322 meters), one of the southernmost volcanoes in the Cascade Range (Lassen Peak is down that way too). Although it is a few hundred feet shorter than Mt. Rainier, it has much more volume. Not only is it the largest volcano in the Cascades, it is the second most active, exceeded in that department only by Mt. St. Helens. Eruptive activity occurs every 600 years or so. The last eruption was an ash explosion 200-300 years ago, possibly witnessed in 1786 (this is disputed; wildfires can look much like volcanic eruptions).

Like any active volcano, Shasta is dangerous. It's not just lava flows (that Hollywood staple), but potential ash flows, and volcanic mudflows (lahars), made all the more likely by the presence of California's largest glaciers around the summit. Many times the lahars occur without eruptive activity (at least 70 times in the last 1,000 years) as glaciers melt in the warmer seasons. Most of the towns near Shasta are built atop lahar deposits (around 10,000 people live in the immediate vicinity of the volcano). 

The pictures in this post are unique in one sense; they were mostly taken from a moving vehicle (by Mrs. Geotripper; I was trying to concentrate on driving). We had come 250 miles already, and had another 250 before we would get home, so we just didn't have time to linger. Driving does give one time to think, though, and I was thinking about the nature of geologic hazards.

We had just spent weeks traveling through a region that could potentially be devastated by an entire buffet of disasters. And yet millions of people live there, either unaware or willing to take the chance in order to enjoy the amenities of living in a coastal paradise, or someplace incredibly green and scenic. I felt no sense of relief from getting out of that danger zone because I understood that any one of those disasters had a very small chance of taking place while I was there. Even if something had happened, we were stocked up and prepared to be on our own for upwards of a week or more. But the clock was ticking, and the longer one stays, the greater likelihood that something bad will happen.

But a geologist's perspective provides little comfort. Going home to familiar ground was no protection from geologic disaster, whether sudden or over decades. I live in a flat and (dare I say it?) boring place, and yet I face geologic disasters every day. I live only about fifty miles from the San Andreas fault, and just twenty or thirty miles from lesser-known but active faults. I live next to a major river that is prone to flooding every few years. My town is just eighty miles or so from a rhyolite caldera that is more active than the "supervolcanoes" of Yellowstone National Park. And for the last four years we have been suffering through an unprecedented drought unlike any ever faced by modern-day California (although precedents exist in the recent geologic past). There's no escaping the Earth, and no one is immune from disaster.

Sutter Buttes from the Sacramento National Wildlife Refuge, the remnants of a Cascades-style volcano in the Great Valley of California. Wait, what? A volcano in the Great Valley???

As we drove through Sacramento in the late afternoon, we could see the very strange skies produced by an out-of-control wildfire in the Coast Ranges. It was too close for comfort, and even as I write this fires are burning very close to the homes of friends in the Mother Lode (100 square miles and only 10% contained), and one of my most precious of landscapes, Kings Canyon in the Sierra Nevada, has gone up in flames (200 square miles already incinerated). In my life, these places will be forever changed, and for the lives of those in the path, their lives will be forever changed.

If geology and earth science teaches us anything, it is that we can't avoid disaster no matter where we go. You don't like earthquakes and volcanoes? Fine. Move to Kansas and enjoy the tornadoes, heatwaves and droughts (I used to say Oklahoma, but they have more earthquakes now than California). Move to Florida and enjoy the hurricanes and the unstoppable rise of coastal flooding. Every place on Earth that I know of faces some kind of event that is incompatible with human existence. And in a strange way, that's what makes us human: we evolved in a dangerous world, and occasionally we are reminded of this in tragic ways.

So how do we respond? Being the teacher that I am, I say the first priority is to educate yourself. Learn what geologic forces influence the place where you live. Learn what the real chances are of such events (don't depend on sensationalist sources in the media or the internet; they want viewership, and aren't really interested in actually educating anyone). Use the resources of the U.S. Geological Survey, or your state geologic surveys (except Oklahoma; for a long time the government there didn't allow the geologists to say that the earthquakes were man-made). Once you know what the threats are in your area, ask yourself what you would do to protect yourself if they were to happen today. Are you prepared? Can you make it through several days or a week or more without water, power, communications? Or the internet? What have you done to be ready? Or, will you be one of the many who will have to wait for the arrival of government assistance?

Am I trying to make you paranoid? Not at all. Paranoia comes from ignorance. If you know what could happen, and you have a plan, you've got the best possible chance to be okay. I can only relate the story of the time I came closest to death. It was two years ago on the Colorado River in the Grand Canyon. Because the river emerges from the deepest parts of Lake Powell, the river is at a constant 47 degrees or so, even when the ambient temperatures in the desert environment exceed 110 degrees. Hypothermia is one of the greatest dangers facing any river rafter. I was anxious about the possibility of a raft flipping in one of the rapids, because more than a few people have died in such circumstances. I worried, but I also practiced in my head, over and over, what I would do if it happened. And I never went into the river without a life preserver.

And of course it happened. We had come through dozens of huge rapids, and one could say that I was almost complacent as we approached Crystal Rapid, one of the two most violent rapids on the river. But the boat flipped in a heartbeat and I was in the river (see the whole story here). Knowing myself, I would have expected to panic, but the mental training took over instead. Although I was in the middle of watery chaos, I was able to get to the overturned raft, which made me easier to find, and I was positioned correctly when I started bouncing off boulders in the river. I was okay in the end, though very shaken. And it was because of the preparation and training provided me by my fellow travelers on the river.

And that's the message I leave with you at the end of this latest blog series. We all live on "dangerous ground". There is no place where we can escape the normal processes of the Earth. But we can choose where to live and what dangers to face, and prepare accordingly. And we can take care of each other when the disasters come.

I hope you've enjoyed the journey! I'll be compiling all the posts in one place soon.

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!

Vagabonding on Dangerous Ground: Landing Place of the Thunderbird and the Grimy One, the Volcanoes of British Columbia

Nch'kay (Mt. Garibaldi) near Squamish, B.C.  Photo by Mrs. Geotripper

t'ak't'ak mu'yin tl'a in7in'a'xe7en and Nch'kay ("Landing Place of the Thunderbird" and "Grimy One") are the Squamish names for two of the most striking volcanoes in British Columbia. Much more recent colonizers refer to the mountains as Black Tusk and Mt. Garibaldi. I prefer the older names; we should name buildings after people, not mountains. They stand at the far north end of the Cascades Volcanic Arc, and although not as well known as their southern neighbors (at least to those of us in the lower 48), they are a potential threat. Mt. Garibaldi, in particular, is seismically active, although it has not had an eruption in about 10,000 years. Debris avalanches are an ever-present problem, however.

Garibaldi is 2,678 m (8,786 ft) in height, and is one of the more unique volcanoes of the Cascades. Much of the mountain erupted on top of a glacial ice sheet, so that when the glaciers melted back, around half of the edifice collapsed in a series of debris avalanches and mudflows. Mass wasting events have continued into modern times, and some of the slopes are considered dangerous enough to limit development in the areas affected. The oldest lava flows date to around 250,000 years ago and are composed of mostly silica-rich lavas such as dacite and rhyolite. The mountain doesn't show much evidence of more violent ash eruptions.

I was incredibly disappointed when clouds obscured our view of Garibaldi on our previous trip through the area, so our trip a few weeks ago was especially gratifying. As it turned out, we took just a few pictures from a pullout with lots of overhead wires, thinking we would get more the next day when we had a few more hours to spare. As luck would have it, the next day was more cloudy...such a surprise in the Pacific Northwest! These were our only pictures of the peak.

The story was very nearly the same with t'ak't'ak mu'yin tl'a in7in'a'xe7en (Black Tusk). We got some distant shots of the peak from the glacial fjord of Howe Sound. The next day we snapped a few pictures as clouds chased around the uniquely shaped summit. As noted in the title of the blog, the name refers to the Landing Place of the Thunderbird. The black color is said to result from the constant lightning strikes associated with the legendary bird.

t'ak't'ak mu'yin tl'a in7in'a'xe7en (Black Tusk), from the Whistler Olympic Venue. Photo by Mrs. Geotripper

The Tusk is 2,319 m (7,608 ft) and much older than Garibaldi. The main peak developed from eruptions around 1.1-1.3 million years ago, forming a stratovolcano. During a subsequent lull, most of the mountain eroded away. The last eruption took place around 170,000 years ago, so the peak is most likely extinct. Other cones in the area have been active in the last few tens of thousands of years.

I was extremely happy to have seen the volcanoes, but I was equally impressed with the other scenery as well. We spent a night in Whistler, and then did something significant: we turned around. The vagabonders were now starting for home, but there was plenty more to see. More posts to come!