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.

Northern Convergence: Leaving a Beautiful Country

How will we deal with the hordes of people from the U.S. trying to invade our borders?

Our trip, the Northern Convergence tour, was not over, but the time had come to cross the border back into the United States from Canada. The trip thus far had been an eye-opener. We had been exploring the "crowded" part of Canada in British Columbia and Alberta, but the land itself exuded wildness and isolation.

We were on the High Plains east of the Rocky Mountains, and had spent the morning at the Head Smashed In Buffalo Jump World Heritage Site, and as gruesome as the name was, it was a fascinating place. From there we headed south to the border crossing at Carway. We figured since it had a name that there would be a town and facilities. We got there, and there was...one building. It was a duty-free souvenir/liquor/tobacco shop, and thank goodness, it had a restroom. Still, there were some picnic tables so we stopped for lunch and had a look around. We also wondered if the authorities were going to let us back into the United States. You never know...in the innocent days before 9/11, we were interrogated about whether we had any "Beanie Babies" in our luggage. I laughed at the question, and the border agent got very serious: "Sir, DO YOU have any Beanie Babies?"

We were not exactly in the High Plains, as the land was broken up into swales and shallow valleys underlain by very soft Cretaceous shale deposits. The shales had been deformed and twisted by the same convergent forces that had lifted the nearby Rocky Mountains, but erosion had smoothed off the sharp edges. The land was semiarid and treeless. More verdant lands could be seen in the distance as we looked westward towards the Rocky Mountains and Waterton-Glacier International Peace Park. Glacier National Park was our next destination.

Chief Mountain was especially prominent on the western horizon. The peak is an outlier of the Rocky Mountains, an isolated upper plate of a thrust fault that had pushed the hard Paleozoic limestones over the softer Cretaceous rock. Erosion had then isolated Chief Mountain as a klippe (see the diagram below).

The mountain was a dramatic welcome back into the United States. We only had a few more days left on our journey, but there was still much to be seen. The story will continue in another post!

Source: http://en.wikipedia.org/wiki/Klippe

Northern Convergence: Tragedy at Crowsnest Pass

Frank was a coal mining town of around 600 people in 1903. The coal seam ran along the base of Turtle Mountain, so the town was established there as well. The Canadian Pacific Railway also crossed the area on its way to Crowsnest Pass.

The local First Nation people did not like Turtle Mountain. They called it the "Mountain that Moves", and refused to camp in the area. The Europeans had no such worries, and mining of the coal was well underway. In the early morning of April 29, 1903, a shift of 17 miners was working deep underground. For weeks there had been strange things happening in the mine. Timbers holding up the tunnel walls would splinter and break for no apparent reason. Coal would occasional "mine itself", crumbling out of the seams overnight when no one was around. Small earthquakes were occasionally felt underground. The miners knew that the collapse of mine tunnels was an ever-present danger, so they may not have been overly surprised to hear the explosive concussion followed by an ominous silence. They were trapped, no doubt by a cave-in. They began to assess their situation. Soon, water was pouring into the tunnels, making a bad situation even worse.

The normal passage to the surface was blocked, but one of the miners knew that a second coal seam might be close enough to the surface that they could hack their way out. They started digging for all they were worth, gasping in the increasingly toxic air. One by one, the miners gave out. They weren't dead, but they just did not have the energy to pick up their tools. Only three of them were still working when they broke through to the surface. Rocks were still falling from above, so they couldn't yet escape, but they had fresh air, and they quickly cut another opening beneath a protective overhang. After thirteen horrible hours they emerged at the surface to find their experience was only a part of an even larger tragedy. A gigantic avalanche had buried part of their town, killing between 70 and 90 people. The miners had been given up for dead, so their appearance was some small bit of good news in the midst of the horrific event.

It gets to a certain point when driving through the mountain wilds of British Columbia and Alberta that one expects that trees will be growing just about everywhere. The region has plenty of precipitation through the year so things will be green. Approaching Crowsnest Pass during our recent Northern Convergence tour, we were struck by the sudden appearance of an absolutely barren slope. It doesn't take long to realize why, as the highway crossed a huge debris field covered with gigantic boulders. It was the debris avalanche that destroyed so much of Frank back in 1903.

http://en.wikipedia.org/wiki/Frank_Slide

The slide was truly epic in scale. Totaling 30 million cubic meters (82 million tons), the avalanche was 1,000 meters (3,300 ft) wide, 425 meters (1,394 ft) high and 150 meters (490 ft) deep. It spread laterally over level ground, covering three square kilometers. The rocks had flowed over the surface like a thick liquid at speeds of up to 70 mph (112 km/hr). The entire event was over in less than 2 minutes.

 The slide was probably inevitable. The limestone layers had been folded into a huge anticline (upward pointing fold) with thrust faults at the base, on top of weak Cretaceous sediments. Glaciation had oversteepened the flanks of the mountain. Fissures sliced deep into the rocks allowing water and ice to accumulate, weakening and wedging the rocks apart. The mining at the base of the slope was quite possibly a contributing factor.

Source http://www.uleth.ca/vft/crowsnest/slidedebate.html

The Frank Slide was the worst mass-wasting disaster in Canadian history. But life went on. The mines were reopened (a horse who worked in the mine was actually found alive after a month underground). The town grew even larger for a few years, but by 1917 the coal mines closed down. Today about 200 people live in the village nearby, and an interpretive center has been constructed that provides information on the extraordinary event.

We headed into nearby Pincher Creek for the night. It was our last night in Canada, but we still had plenty yet to see, on both sides of the border..

Source: http://occ.crescentschool.org/geography/physical/folding/frankslide.html

Northern Convergence: Athabasca Glacier, at the Front Line of Climate Change

Athabasca Glacier and Sunwapta Lake in July 2014

Athabasca Glacier in Jasper National Park is one of the few places in the world where one can drive to a glacier. It is also one of the most vivid places to see the global warming in action.

We were in the midst of our Northern Convergence journey through British Columbia and Alberta last July when we pulled up at the visitor center for the Columbia Icefield. Up to this point we had seen a large number of small glaciers tucked away in the high peaks of Yoho and Banff National Parks, and we had seen plentiful evidence of past glaciations at nearly all the localities we had been visiting over the previous six days. But here at Athabasca Glacier, we were confronted with ice. Lots of ice, just a short distance from the end of the road. It was not unlike stepping out of a time machine into the last ice age.

Athabasca Glacier in 1919. Sunwapta Lake does not yet exist.

One of the first issues that we were confronted with is global climate change. The Earth is warming up at an alarming rate, and the warming couldn't be made clearer than the fact that Athabasca Glacier is shrinking. Since the 1800s the glacier has receded more than a mile, forming a new lake, Sunwapta. It was visibly shorter than it was on my last visit in 2005 (see a comparison below).

We took in a brief overview of the glacier from the visitor center complex along the highway. We then crossed the highway and parked at the base of the rocky knob in the photo above.

We started up the trail, which was steep in a few spots, but not overly difficult. 

Looking behind as we climbed the slope we could see Sunwapta Lake, which did not exist prior to a few decades ago. Note the barren flats. There should be trees growing at this altitude, but the rocky debris and till has not had time to develop soils. This is a newly exposed landscape.

A marker along the trail appeared. It's message was rather stark. Only three decades ago, ice covered this spot.

The bedrock marks the passage of the ice in the form of striations (scratch marks from sand particles in the ice), and grooves.

We reached the top of the hill, where the ice existed as recently as 1992. Despite the decline in the size of the glacier, it is still an impressive sight. The ice ranges in thickness from 300 to 1,000 feet (roughly 100 to 300 meters). The crevasses mark the places where the ice is moving over a steep dropoff.

Large lateral moraines line the sides of the glacier. If it were not receding so rapidly, it would also have a terminal moraine around the end.

As we approached the terminus, we could see the swollen river of meltwater emerging from the ice. The river blocked easy access to the ice. There were a few boards to make a rudimentary bridge, but sternly worded signs warned of the dangers of actually going out onto the ice itself. Death, you know, from falling into crevasses and through thin ice (and yes, it happens).

Compare this photo to a shot from the same spot in 2005, below

The entire area covered by the river water had been covered at the time of my visit in 2005. Getting on the ice was easier, even encouraged, at the time. Not anymore.

Athabasca Glacier terminus in 2005

Much of the snout of the glacier was covered with dirt, boulders and debris exposed as the glacier melts.

The glacier is "fed" by the Columbia Icefield, a vast expanse of ice covering 125 square miles (325 square kilometers) between some of the highest peaks of the Canadian Rockies. Six major glaciers flow from the huge mass of ice coating the high divide. Meltwater from the glaciers flows to the both the Pacific and Atlantic Oceans, as well as Hudson Bay and to the Arctic Ocean (thanks, Howard, for the correction). The icefield lies east of a gap in the Columbia Mountains that allows Pacific storms to drop prodigious amounts of snow each year, around 30 feet (ten meters).

In some places the chunks of ice simple fall off the cliffs into the cirques below. I saw one of these icefalls on my earlier visit, and was watching closely this time around, but no dice this year.

At the rate that the glacier is receding, it will probably be gone by the end of the century. There can hardly be a starker piece of evidence that the Earth's climate is warming. It is as plain as the nose on  one's face, unless you are a politician whose re-election depends on funding from lobbying groups who are paying you to be blind.

We returned to our vehicles and drove down the Icefields Parkway to a new destination: the High Plains of Alberta. We were on the trail to find some dinosaurs...more later.

Northern Convergence: Finally Finding the Edge of North America at Yoho National Park...600 miles inland

Looking upstream on the Kicking Horse River at Field, B.C.

How strange geology is, and what wonderful journeys it provides for our imagination! So many geological processes are exceedingly slow, and yet over time incredible changes occur. How can I be talking about the edge of the continent when we are 1,000 kilometers (~600 miles) from the nearest shoreline?

I've called this narrative of our journey "Northern Convergence" because of the presence of a convergent plate boundary for the last 200 million years or so that has drastically altered and changed the continental margin of Canada and the Pacific Northwest. We had spent the previous four days traversing landscapes composed of exotic terranes, tracts of crust that originated someplace else and had been appended to the edge of the continent by way of subduction. The bits of crust were dragged into the trench, but were too buoyant to sink into the underlying mantle, so they mashed into continent instead, and intense deformation resulted. And the continent got bigger...lots bigger.

Looking downstream on the Kicking Horse River at Field, B.C.

We had crossed the Insular, Coastal, Intermontane and Omineca belts in our four days of driving, covering some 1,000 kilometers (600 miles), and we had finally reached the Canadian Rockies at Yoho National Park. It was here that we finally first encountered the ancestral edge of the North American continent. The limestone and and other sediments in the cliffs high above were deposited in a passive margin setting consisting of debris washed from the ancient continent around 900-400 million years ago. Everything west of our location was from someplace besides North America!

The scenery was on a truly grand scale. Yoho is contiguous with Banff National Park, and yet is rarely mentioned in the same breath (it's always "Banff and Jasper", maybe because they're on the Alberta side, and Alberta knows P.R.). Yet the park is spectacular, and even better, holds a treasure of worldwide significance.

The park protects mainly the upper watershed of the Kicking Horse River which includes several major icefields, including the Waputik and Wapta. The glaciers coming off the icefields contain finely ground silt and clay that stay suspended in the turbulent water. The rivers look like flowing milk at times.

Glacial "milk" also changes the appearance of lakes. In the calm water some of the clay begins to settle out forming a translucent turquoise color that is very striking. We made a stop at Emerald Lake to talk about the glaciers and have a look at the high ridge where the Burgess Shale was exposed.

Another road reaches up into the Yoho River drainage, providing access to Takakkaw Falls, the third highest in Canada at 254 meters (833 feet). The waterfall is a textbook example of a hanging valley, resulting when the main trunk glacier carved a deeper valley than the tributary glacier. The glacier feeding Takakkaw Falls is only a kilometer or so upstream of the brink.

If you need a sense of scale regarding 254 meters, look at the picture above where the water leaps outward from the cliff near the top of the waterfall. Let's zoom in on it. Those little dots to the left? Rock climbers!

All in all, Yoho National Parks is one of the most dramatic landscapes imaginable, but it's the rocks themselves that hold the real treasure. Although mining took place here last century, the treasure is in the fossils found in these rocks. About half of our crew were not with us as we toured the park, as they had left early in the morning to complete a tortuous 12 mile hike to see the quarry where the Burgess Shale fauna was discovered more than a century ago.

There is a problem with understanding the ecosystems that existed millions of years ago. Usually only the shells and bones are found, but the vast majority of organisms had soft bodies that are rarely preserved as fossils. They would invariably decay quickly. Fossil localities with the remains of soft-bodied organisms are few and precious, and our students were investigating one of the world's most famous. The Burgess Shale preserves the fossils of soft-bodied organisms that were present only a few million years after the dawn of complex multi-celled lifeforms.

How did they come to be preserved here? Just over 500 million years ago, the region was at the edge of the continent in relatively shallow water at the edge of the continental shelf. The shelf was unstable and occasionally a mass of mud would break off and sink into deeper water, carrying with it the organisms that were living there. The blocks sank into oxygen-starved water where the bacteria that would have consumed the soft body tissue could not survive. Mud covered and preserved the dead organisms. More than a hundred species have been described here.

The fossil quarry lies high on a ridge above Emerald Lake between Field and Wapta peaks. You can pick it out in the picture below, as the horizontal gash in the hillside with the lowest patch of snow. The hike is not easy, really an all-day affair. The quarry is a World Heritage Site and access is strongly restricted, and obviously collecting is not allowed. I've heard they've even gone after fossil sellers active on E-Bay.

I did the hike in 2005, so I didn't try it this time, opting instead to let my fellow professor hike with the students (she might forgive me the blisters one of these days...). The hike was one of the great adventures of my life, though, and I described it in detail in a post last April: you can read it by clicking here. There just aren't many times in life when you can be so close to the ancient past.

Holding a specimen of Marrella splendens in the Burgess Shale quarry, 2005

We visited with the local wildlife, and then headed over Kicking Horse Pass into Banff National Park. More adventures lay ahead!

A Black-billed Magpie (Pica hudsonia) at Field, B.C.

I hope that somebody appreciates that I made it through an entire post about a place named "Yoho" with nary a single "Pirates of the Caribbean" joke.

Northern Convergence: The Mystery Photo Explained

Thanks for all of your conjectures about yesterday's mystery photo! The Earth is such a fascinating place, and there are so many different kinds of strange patterns that have different origins. Let's review some of the guesses (and they were very good, by the way):
a. Sinkholes and karst topography
b. Bison wallows
c. Ground squirrel or prairie dog workings
d. Periglacial patterned ground
e. Dried marshes, evaporative processes
f. Pithouses

Take a look at the depressions from ground level. The rocks are gravel and sand, so karst is not likely (sinkholes most often result from the collapse of caverns in areas underlain by limestone). Something like a buffalo wallow makes some sense, but these are very concentrated, and the region is not really good buffalo habitat (too much mountain slope and not enough prairie). Rodents like prairie dogs or gophers tend to produce mounds (so called 'mima mounds') rather than hollows. The location of the site on a high river terrace tends to rule out the idea of swamps or evaporative processes.

Of the natural processes that could make this phenomena, periglacial processes make the most sense. Freezing and thawing of soils often result in rings and polygons that might resemble what we saw in the picture. The region underwent glaciation in the Pleistocene epoch and continues to have extremely cold temperatures in winter. It makes some sense, but then why are the pits filled with so many artifacts?

So yes, these pits are made by humans. We were paying a visit to the lands of the Xwisten people, a First Nations group whose traditional lands were along the Fraser and Bridge Rivers near Lillooet, British Columbia. This river terrace surface contains the remains of dozens of pithouses.

The former village along the Bridge River is the site of ongoing archaeological excavations by researchers and students of the University of Montana as well as local members of the Xwisten tribe.

We were being led on a tour of the archaeological site by several members of the Xwisten Bridge River Band who had been involved in some of the excavations. The setting was dramatic, with high mountain peaks on all sides.

As is the case with most archaeological digs these days, only a small portion of the site is being studied in detail. There is an expectation that future technology will be able to better analyze the site, so much of the village remains undisturbed for the time being. Only one of the pithouses was exposed when we visited.

The village site was abandoned over a century ago, although many Xwisten live in a modern village just a few hundred yards away. Evidence from the site investigations show nearly continuous occupation of the site beginning about 1,800 years ago. Many of the sites were used over and over, with some of the pits containing 12 levels of occupation.

A few years ago the Xwisten decided to build a pithouse on the site using the knowledge of their elders. One of our guides noted that what took their ancestors several weeks to construct took them more like three years even though they had modern tools. Entry was usually through a square hole in the room, although some may have had side entrances. The ladders, as you can see below were notched logs. With well insulated ceilings the pithouse seemed like it would be roomy and warm in winter conditions.

The Xwisten subsisted in part on salmon, and part of the demonstration was the preparation of salmon for eating and preservation. Our tour concluded with a salmon dinner. The sun was getting low, and we had another two hours of highway ahead of us. We drove into the night arriving at our hotel in Kamloops sometime after ten o'clock. It was a long, but fascinating day. We had left the Coastal Belt and were now making our way through the Intermontane Belt. We'll pick up the story in the next post!

To AF, the commenter in the last post who lives in Lillooet, let me know if I got anything wrong! Our visit was very quick, and I'm just a geologist, not an anthropologist!