Tuesday, August 20, 2019

Travels in Cascadia: Victoria B.C., the City of Mutton Rocks

The next stop in our recent travels through Cascadia was the city of Victoria on Vancouver Island in British Columbia. We got there by way of a ferry from Port Angeles, Washington, as described in the last post. Victoria is an attractive city, one of the most temperate in Canada, given its location on the Pacific shoreline (the adjacent ocean moderates the seasonal temperature extremes). It is also unique in another respect. The city is partially constructed on bedrock (the solid rock that underlies surface soils and sediments), and the land was under a vast 1,000 meter thick ice sheet only 14,000 years ago.

This geologically unique combination means that Victoria is sort of a city of mutton rocks.

I imagine that sentence needs explanation...

The term roche moutonnée describes an asymmetrical glacially scoured rock outcrop that has a smooth slope on the side facing the flowing ice, and a steep cliff on the side where the glacier pulled away from the outcrop ("stoss and lee structure" is a related term). The scale can range from a few meters to many hundreds. They are common features in regions of bedrock that have been scoured by massive continental ice sheets, such as happened in Victoria. One of the tallest hills within the city, Mt. Tolmie (below), is an excellent example. In the picture one can see the gently sloping forested flank on the left side of the hill, and the steeper plucked side to the right.
Mt. Tolmie, a roche moutonnée in Victoria

The problem with roche moutonnée as a geological term is that we geologists can only barely agree on its meaning. It's derived from French, and the "roche" part isn't a problem. It means "rock". But "moutonnée" is the tricky aspect. It can be translated loosely as "sheep" (think "mutton""), but not exactly (French: "mouton"). Moutonnée (with the extra e's) translates to "frizzy", and is taken as a reference to sheep's wool. The term originated in the 1700s with a naturalist named Horace-Bénédict de Saussure (it would be decades before the term "geologist" was coined) who noted that the rocks looked like a type of wig apparently well-known at the time whose locks were held in place with mutton grease. Except that there seem to be few or no references to wigs that were actually called that (the closest version was a tête de mouton).

So we teachers are left with trying to define the term as meaning "rock sheep" based on the nebulous idea that the rocks look like sheep grazing in meadows. Which they really don't. But it's still easier than trying to describe obscure French wigs from the 1700s and mutton grease.

There are consequences to building on such rocky landscapes. There are plenty of large patches of glacial till that are easy to plane off with a bulldozer for building construction, but when the rock crops out, allowances have to be made. Perhaps it might involve blasting to construct a flat foundation. The rock is pretty tough stuff, gabbro, diorite, and greenstone of the Wrangellia terrane, dating back to the era of dinosaurs.

There are problems in this kind of situation. When the Empress Hotel (see the picture above) was constructed in 1904-1905 it was placed partly on solid rock and partly on mud-rich sediments. Complications quickly ensued. The south part of the building subsided several centimeters within the first year and ultimately sank about a meter. It's a real headache for those who must maintain the building.

Still, Victoria is a truly beautiful city, and the city has a unique personality. The city has miles of coastline, and there are dozens of scenic shoreline parks. We pulled up at Cattle Point to look at smaller roches moutonnée along with glacial scour marks and striations. Strangely enough, there was a piano sitting on the bluff. It was brightly painted, there was a bench, and the piano was in tune! I wondered what was going to happen to it if it rained, but then noticed a waterproof cover. We later found that there are five such pianos in the parks, and we were actually treated to a tune by a passing jogger, followed by a song by one of our students!

If you ever have a chance to visit Victoria, enjoy the city, but be sure to follow the shoreline drive to see the glacial heritage of the landscape (as well as seeing some dramatic coastal scenery). But the other thing you should do is to hike or drive to the summit of the mutton rocks of the city. Mt. Tolmie is a good choice within the city limits, or you can go just north of the city to the much higher summit of Mt. Douglas. It's a short hike from the parking lot to a summit with a 360 degree view of the region. The Olympic Mountains are visible across the Strait of Juan de Fuca to the south beyond the city, and the many islands of the Strait of Georgia and Saanich Inlet are visible to the north and east. Glacial polish, striations and grooves are present underfoot.

On the day we were there, I saw some unusual looking clouds far to the southeast. I took a few highly zoomed shots and forget about them until weeks later. I started working with the contrast and exposure of the picture and realized I had captured an image of Mt. Rainier across the Puget Sound. The volcano is more than 130 miles away (below)!

I had three main resources for the geology in and around the city:
The Geology of Southern Vancouver Island by Chris Yorath
Roadside Geology of Southern British Columbia by Bill Mathews and Jim Monger
Geology of British Columbia, A Journey Through Time by Sydney Cannings, JoAnne Nelson, and Richard Cannings.

Friday, August 16, 2019

Geotripping! It Could Be You! Geology of the Eastern Sierra Nevada, September 26-30

The east side of the Sierra Nevada and the adjacent Owen's Valley is one of the most dramatic landscapes on planet Earth. The valley that forms the eastern boundary of the range is two miles deep, twice the depth of the Grand Canyon. The valley contains active faults (responsible for one of California's most powerful earthquakes ever, the 1872 Lone Pine quake), and active volcanoes, ranging from small cinder cones to gigantic calderas that rival those of Yellowstone.
The region is full of fascinating geological features, including Bodie, one of the most well-preserved ghost towns in the American west. There is also the nation's "Dead Sea" which is not really dead at all, preserving the lives of millions of migratory birds. Mono Lake is the epicenter of the LA water wars, an issue that can only become more important as California enters a new and unprecedented climate regime.

Scenery abounds, and tourists and explorers love this region like few others. But how often have people traveled through this region without the awareness of the incredible geology exposed at their feet? Are you one of them? Have you never had the privilege of exploring this incredible landscape? Well, I've got a great opportunity for you...
On September 26-30, the Geology Department at Modesto Junior College will be offering Geology 186, a 2-unit field course on the geology of the eastern Sierra Nevada and the Owen's Valley. We'll leave the college early Thursday afternoon and drive to our expected first night stop at Baker Station, the High Sierra Institute, located in the high country of the Sierra near Sonora Pass. The facility is run by our district for a variety of multidisciplinary classes.
From there we'll cross the Sierra Nevada at Sonora Pass and explore the lands to the east, including Bodie and Mono Lake before arriving at our base camp at Millpond Recreation Area just outside of Bishop in the Owens Valley. We'll spend three days there. We'll check out the Long Valley Caldera, the Volcanic Tableland, Devil's Postpile, Inyo Craters, and Minaret Summit the next day.
The following day we'll head up into the White Mountains across the Owens Valley from the Sierra Nevada, where we'll have a bird's-eye view of some of California's remaining glaciers, and have a look at the oldest trees on the planet. We'll then head south to Lone Pine and Owens Lake.

Our final day we'll head back up through the caldera with a stop at Convict Lake (below) and then make our way home via Tioga Pass and Yosemite National Park.

We'll be camping out, and you'll be your own cook on this trip. We'll travel in school vans. The trip will cost $80 plus the cost of tuition at MJC (about $100 or so). Information can be found at http://hayesg.faculty.mjc.edu/Eastern%20Sierra%20Nevada.html, and the MJC website (to enroll in the class) can be found at https://mjc.edu/. If you live in the Modesto area, we'll have an organizational meeting on Thursday, September 12 at 5:30 PM in the Geology Lab at MJC, Science Community Center 326. If you live outside the area, I can send you the relevant materials.

The Sierra Nevada and Owens Valley is an incredible place to explore. I hope you'll be joining us!

Wednesday, August 14, 2019

Travels in Cascadia: Traversing the Salish Sea, and Leaving the USA

Morning in Port Angeles, looking across the Salish Sea

It was the third day of our journey through Cascadia, and after our exploration of the Olympic Peninsula, it was now time to leave the United States. We were in Port Angeles, Washington at the north end of the peninsula, and our route to Canada was by way of ferry across the Strait of Juan de Fuca. The landscape was undergoing a dramatic change. First of all we weren't in mountains anymore, we were crossing a sea. That seems an obvious point, but one has to wonder why the mountains abruptly end in a sea, and why similar mountains don't occur across the water. Second, we had reached the southern reach of the vast ice sheets that covered Canada and part of the United States during the Ice Ages that ended only around 12,000 years ago.

These two things, the end of the mountains and the end of the glaciers are related. The Strait we were crossing, along with the Strait of Georgia and the Puget Sound, are collectively known as the Salish Sea. The term was coined in the late 1980s as a way of recognizing the interconnectedness of these bodies of water as a single environmental entity. The name originated with the indigenous people who first colonized the landscape around the sea.
The Salish Sea (from http://blogs.agu.org/fromaglaciersperspective/2015/06/08/salmon-challenges-from-glaciers-to-the-salish-sea/)
The Salish Sea covers about 17,000 square kilometers (6,600 square miles), and has 7,470 kilometers (2,900 miles) of coastline, along with 419 islands. It is a unique ecosystem, a sea in the Pacific Northwest that is somewhat protected from the worst storm violence and wave action out of the Alaska region. Something like 8 million people call the shoreline home, in a megalopolis that extends from West Vancouver to Olympia. Along with people, there are 37 species of sea mammals, 172 species of birds, 247 species of fish, and over 3000 species of invertebrates.

The western margin of the Salish Sea is formed by the Olympic Peninsula and the mountains of Vancouver Island. The Strait of Juan de Fuca slices between the two landmasses. It was the strait that we were traversing on our way to the city of Victoria. 

The Olympic Peninsula is made up mostly of ocean floor sediments and basaltic rock pushed up as material was stuffed into the trench. Vancouver Island has a different origin. It is a piece of continental crust that traveled across the Pacific (at the feverish rate of a few inches per year) only to collide with the western edge of North America. Such far-traveled landmasses are called exotic terranes.

Source: http://www.deq.idaho.gov/regional-offices-issues/coeur-dalene/rathdrum-prairie-aquifer/geologic-history/
The Salish basin was shaped in large part by the ice sheets that covered essentially all of Canada and a good portion of the northern United States. As recently as 12,000 years ago, a mass of ice a mile (1.6 km) thick pushed south through the basin as far as Tacoma. A lobe of ice also extended west through what would become the Strait of Juan de Fuca.

The ferry ride took about 90 minutes to cover the 20 miles of open water between Washington and Vancouver Island. It's a beautiful ride, made all the more interesting as one realizes this entire body of water was once covered by ice. As one gets further out to sea, the higher snow-capped peaks of the Olympic Mountains come into view.

It may be that the water can get pretty choppy, especially during winter storms, but on my four trips across the strait, conditions were very calm. I almost felt like I was on a lake instead of a sea. We were still on dangerous "ground", though. The Strait of Juan de Fuca is not immune to the effects of huge earthquakes, whether in the immediate vicinity (along the Cascadia Subduction Zone), or from those at great distances (such as the 2011 Tohoku earthquake in Japan). The problem, of course, will be tsunamis.

Sometimes confined bodies of water can weaken the effect of tsunamis by dispersing the energy of the waves, but in some circumstances they can magnify the energy instead. There is some evidence of ancient tsunamis along the shorelines of some of the interior islands of the Salish Sea. The effects will probably muted compared to the damage along the Pacific Coast, but more developments are located there as well. On a positive note, the cities in the region are recognizing the threat and are talking action to minimize the damage (see an example here).
It was a beautiful cruise. Soon, we pulled into the harbor at Victoria and got ready to disembark. We were in Canada!

This post is part of a series on our field study of the geology and anthropology of British Columbia and the Pacific Northwest.

Monday, August 12, 2019

The 35 Year Wait is Over! The Ribbon-cutting for the Great Valley Museum Outdoor Nature Lab is Wednesday!

Ever since the origin of the Great Valley Museum decades ago, there has been a desire on the part of the faculty of Modesto Junior College and Great Valley Museum staff to have an outdoor education area that would complement the nature exhibits inside the museum. For decades the museum operated out of a former house across the street from the MJC East Campus, and other than a few plants alongside the building, there was no outdoor component to a museum visit. Big changes came with the passage of Measure E in our county that led to the construction of the Science Community Center with a vastly expanded Great Valley Museum that included a planetarium, Science on a Sphere, and other innovative exhibits. However, the Outdoor Nature Lab was one of the last of the Measure E projects to receive funding, and for several years the very existence of the lab was in question.

But that finally changed and two years ago we finally broke ground for the construction of the outdoor lab, after a wait of at least 35 years. There are a few finishing touches still to be added (interpretive signs, and believe it or not, a big dinosaur), but it is officially opening to the public this week. It's fair to say that it opened up to nature months ago...a pair of Killdeers raised a family during the early summer, and other animals are taking up residence. But the official opening is this week for we humans.
Please join us! The ribbon-cutting ceremony will take place on Wednesday, August 14, at 9:00AM. The GVM Outdoor Nature Lab is on the north side of the Science Community Center on MJC's West Campus. It's been a long journey and we can't wait to share it with you!

Thursday, August 8, 2019

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: How Far Can You Spit? Here's one of the Longest Spits, at Dungeness

I was never a good spitter. We had a hazing ceremony back in the scouting days where we were blindfolded and had a spitting contest. When one of us let loose a big one, everyone started shouting about how far it went, and how it disappeared over the horizon. "It must be going around the world" someone said, and thus we knew we were about to get hit with a pail full of water from the back.

Of course this post isn't about THAT kind of spit. It's something very different. Take a look at the picture above. It's the Dungeness Spit Lighthouse on the Olympic Peninsula in the vicinity of Port Angeles in Washington. If the picture is a little fuzzy, it's because it was taken at extreme zoom. So we'll back up a little. Those snow patches in the distance are on the slopes of Mt. Baker, a stratovolcano of the Cascade Range.
As we pull back even further, one starts to wonder what the lighthouse is built on. Is it an island? Not exactly. If you look carefully to the left you can see a very narrow strip of land. Follow that narrow strip into the next picture...
...and you can see that this narrow strip of land is connected to the coastal bluffs at Dungeness National Wildlife Refuge (yes, the crab is named after the area). It's no more than a hundred or so feet wide.

What is this five and a half mile strip of land made of? As it turns out, it's mainly sand and gravel. And that is what a spit is, a long narrow strip of sand connected to a shoreline and extending out into the water. The Dungeness Spit is the longest spit in the United States (Long Beach in southern Washington has the appearance of a spit and is longer, but it is partly composed of solid bedrock beneath the sand and doesn't quite meet the definition).

Sand migrates along shorelines because waves often wash up the beach at an angle but flow straight off the beach. In that way, the sand zig-zags along the beach in a process called longshore transport or beach drift. The movement of sand is continuous, and if the beach sands aren't replenished by river sediments the beaches can become more narrow or disappear entirely (dam building in the last century on most major rivers has led to beach declines across the country's shorelines).
Sometimes there is a sharp turn in the shoreline, or a large bay opening, and turbulent energy is lost as the wave refracts around the turn. The sand is deposited as a bar. The bar grows as more and more sand is added. Bays can be completely blocked by the spit unless rivers provide enough outflow to keep the bar clear. Several of these so-called baymouth bars can be seen in Northern California at Humboldt Lagoons State Park (see some pictures at this link...plus a bonus bad joke).
The Dungeness Spit has an interesting source of sand. During the ice ages more than 13,000 years ago the south end of the continental ice sheet covered this area (it covered the entire Juan de Fuca Strait). The weight of the thick ice pushed the crust of the earth downward hundreds of feet. As the ice age ended, large rivers flowing off the Olympic Mountains built up a large delta of gravel at Dungeness. The gravel was essentially at sea level but the crust rebounded upward forming a coastal terrace several tens of feet high (see the picture below). Waves cut into the terrace, forming the coastal bluffs, and providing a plentiful supply of sand for the Dungeness Spit. At 5.5 miles it continues to grow at around 14-15 feet per year. Heavy storm waves can break through the spit, but sand refills the gap relatively quickly.
The prevailing waves can change direction at times, and so a secondary spit has formed within the coastal side of the Dungeness Spit. It's called the Graveyard Spit, and it can be seen clearly in the Wikipedia picture below. It is fed by sand coming around the end of the Dungeness Spit.

It's not hard to get to the spit. There is a campground and a parking area for the Dungeness National Wildlife Refuge (the enclosed bay is a protected area; more than 200 bird species are known from the area). From the parking lot a half-mile long paved trail wanders through the forest to an overlook where I got most of the pictures seen above. From there you can walk down to the beach and walk as far as you wish out onto the spit. If you are ambitious enough, you can get to the lighthouse for a tour. It dates from 1857 and is the second oldest lighthouse in the state. It is staffed today by volunteers.
Source: Wikipedia

This post is part of a new series about our recent field studies course to British Columbia and Washington. Next stop: Olympic National Park!