Travels in Cascadia: Gigantic Floods and Tallapus Meet at Willamette Falls

It's not fair, but I don't spend much time in Portland, Oregon. It's not that I don't like Portland, I just don't know it because the logistics of my normal travels rarely allow me to stop there. We are always three or four hours away from our destination and worried about getting through town without getting stopped in one of Portland's legendary traffic jams. But on our way to meet our students in Seattle for our field studies trip to British Columbia we decided to stay in Portland, ostensibly to get nice pictures of Mount Hood. We were moving along Interstate 205 and the traffic wasn't too bad, and saw a wayside viewpoint and pulled off. It was there that I discovered for the first time the work of Tallapus (Coyote) to help the Clackamas people procure a secure food supply of salmon and lamprey: Hyas Tyee Tumwater, otherwise known as Willamette Falls. It's the second largest waterfall in the United States after Niagara. It's 1,500 feet wide, drops around 40 feet, and has a flow that averages about 30,000 cubic feet per second.

What? You've never heard of it? Neither had I. I would have thought that the second largest waterfall in the country would have attracted a bit more attention among travelers, but there are reasons that it is not all that familiar. Some of the reasons go right to the heart of cultural conflicts between European colonizers and the original inhabitants of the region.

The Willamette River is a major tributary to the Columbia, providing around 10-15% of its total flow. Major rivers don't tend to have waterfalls unless unique geological conditions exist. And the story of the Willamette is pretty wild. The river is one of the few north-flowing rivers in the country, following a geologic trough related to the actions of the Cascadia Subduction Zone. In other words, the valley of the Willamette River was not carved by the Willamette River. The valley is weird in some other ways...there are fine silt layers covering much of the valley floor, but scattered here and there are hundreds of gigantic boulders weighing as much as 170 tons. Boulders that came not from the adjacent Coast or Cascades Ranges, but from Montana and Idaho! How can these things be explained?

The silt would normally be easy enough to explain. Geologists would assume that such sediments represent floodplain deposits of the Willamette, but they're not. The bedrock floor of the valley beneath the silt is actually composed of layers of basalt lava that erupted all over Washington and Oregon around 16 million years ago. The origin of the silt and the giant boulders are related one of the most incredible geologic events ever to effect Washington and Oregon. Considering the presence of giant volcanoes, gigantic rivers, and major subduction zones and earthquakes, that's saying a lot.

Between 15,000 and 13,000 years ago, the Pleistocene Ice Ages were beginning to wane, but an edge of the gigantic ice sheet that covered most of Canada flowed into Idaho and Montana and blocked of a major river drainage. A massive lake, now called Lake Missoula, formed behind the ice dam. The volume of the lake grew to 500 or 600 cubic miles of water, but then the ice dam destabilized and collapsed, sending a massive flood amounting to about ten times the combined flows of all the rivers on Earth racing across the plains of eastern Washington. The raging waters careened through the Columbia River Gorge at depths of hundreds of feet and the flows backed up into the Willamette River Valley. The muddy waters settled out, forming the silt layers covering the valley floor. The boulders arrived encased in icebergs in the turbulent currents. As the ice melted the boulders dropped out. The ice dam re-formed dozens of times and floods occurred at intervals of 50 or 60 years for around 2,000 years.

As the floodwaters receded the lava flows were exposed and then eroded by the waters draining from the Willamette. The ledges of lava became Willamette Falls.

So why isn't the second largest waterfall in the United States not a major national tourist attraction, like Niagara Falls? The basic reason is that although waterfalls are scenic and all, they are also a resource, and if humans of all cultures have anything in common, it is that if a resource is available, it will be utilized. For the Clackamas Chinook people and others in the region, the resource was food. The falls were a chokepoint on the Willamette, a barrier to the movement of salmon and lampreys upstream. Both fish could get past the falls, the salmon by jumping from one particular ledge/pool to another, and the lampreys by using their sucker mouths to climb the wet rocks. But the animals would be concentrated at the falls where they could be easily captured. The falls were considered a gift from Tallapus, and a number of villages were present in the area. The Clackamas had a surplus of salmon that they were able to trade with other tribes in the region.

Source: By M.O. Stevens - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=6816704

To American and European colonizers, the falls meant something different: power. The Native Americans had been decimated by European diseases like smallpox even before first contact, so were able to offer little resistance to the sweeping changes the colonizers brought to the waterfall. A flour mill came first in 1844, followed by paper mills beginning in 1866. A system of locks to allow upstream ship traffic was constructed in 1873. Hydroelectric generating stations arrived in 1888 and 1895. The developments destroyed the salmon runs, so a rudimentary fish ladder was blown out of the basalt in 1882. A more modern fish ladder was constructed in 1971. The flour mill was removed to make room for the paper mills, which operated until 2011. The ship locks were shut down in 2015. Only one of the power stations remains. In other words, the Willamette Falls today look like a nearly abandoned factory slum, which it technically is.

Most of these abuses are not visible from the overlook at Interstate 205. One wishes that with most of the ugly factories abandoned that the river and falls might be returned to a state resembling the primeval river. There are plans to "develop" the site with river walks and interpretive signs, but of course in the current culture of capitalism, also businesses and tourist attractions. It its own way tourism is a resource like any other, a commodity to be exploited.

In the end, I hope the stories will remain. The story of how Tallapus scooped out part of the river to slow down the migration of the salmon and lampreys so the people could catch some of them. And the story of how awesome, almost incomprehensive forces were unleashed by nature to form the falls through lava flows, glaciers, and gigantic floods.

Source: Army Corps of Engineers

America Has Other Volcanoes: Airliner Chronicles Visits Mt. Hood

The tragic and yet fascinating activity on the Big Island of Hawai'i has focused attention on volcanism in the United States, and has served to remind us that Hawai'i isn't the only place in the country that has to face up to the hazards of living in the shadow of dangerous mountains. I traveled to Washington by plane last week and was lucky enough to capture images of several of the volcanoes of the Cascades. We looked at Mt. Rainier first, and then at California's largest yet little-known volcano, Medicine Lake Highland. I really wanted to show some shots of St. Helens but we flew right over it, so I cheated and used some shots from 2006. But I wasn't disappointed by Oregon. The face of Mt. Hood was still illuminated by the rapidly setting sun.

Mt. Hood is the headache for emergency planners in Portland and the small villages south of the Columbia River. It is the highest mountain in Oregon at 11,249 feet (3,429 meters). The upper slopes are extremely rugged and steep and as such present a serious threat of debris avalanches similar in nature to that which destroyed the summit of Mt. St. Helens in 1980. The scar of the most recent avalanche can be seen on the right side of the summit in the picture below. The slide took place about 1,500 years ago. The prominent spike of rock in the alcove is called Crater Rock, and it is the remains of a lava dome that erupted around 1781. An earlier avalanche around 100,000 years ago removed the north flank of the mountain and flowed down Hood River Valley and across the Columbia River.

The thick mantle of snow presents the other serious hazard, that of lahars, or volcanic mudflows. The fluid masses have reached the outskirts of Portland in the past, and some lahars have occurred in recent years even though no eruption took place.

Living near volcanoes doesn't and shouldn't mean living in constant fear, but it is important to be aware of the potential threats where you live, and an understanding of what you will need to do in the event of an eruption. And because of all the crap roiling around on the internet, get your information from the geologists who work for the U.S. Geological Survey or state surveys in your area. Always be aware of the potential of exaggeration in the media, because even if they present good information, it will be cloaked in clickbait-style headlines that they utilize to get attention these days.

Meanwhile, the plane continued southward, and another volcano or two could still be discerned in the fog and mist. My mention of the Airline Chronicles refers to my first blog series that started way back in 2008. Some more information on Mt. Hood is available at  https://pubs.usgs.gov/fs/2000/fs060-00/.

A Convergence of Wonders: Day 3, Driving Across the Subduction Zone

So what is convergence? The word can have many meanings, but in geology, convergence refers to regions where the plates of the Earth's lithosphere (the solid layer of crust and upper mantle) are forced together. When two continents converge, huge mountain ranges like the Himalayas and the Alps are formed. When oceanic lithosphere is forced into continental lithosphere, the denser and thinner oceanic rock is forced under the continent in subduction zones, where parts of the plate melt and form magma bodies (plutons) which rise into the continental crust, ultimately forming volcanoes and masses of plutonic rock like granite and diorite (like those of the Sierra Nevada). Besides volcanism, subduction zones are responsible for huge earthquakes like those that ravaged Japan this year and Indonesia in 2004.

This series of posts is called a Convergence of Wonders because much of the landscape we traversed on our trip was influenced by the subduction zone (the convergent boundary) that has been active off the coast for the last 200-300 million years, right up to the present day. It is called the Cascadia Subduction Zone. On the third day of the trip we got as close to the subduction zone as we could, crossing the Cascades and setting up camp on the coast at the mouth of the Columbia River. Our destination at the end of the day was the ominously named Cape Disappointment.

Our first stop was a delightful spot I had not seen before, Smith Rock State Park near Bend, Oregon. I've been guilty of thinking of parts of central and eastern Oregon as being relatively featureless basalt flows in monotonous horizontal layers. This isn't actually true, and Smith Rock is one of those incredible exceptions. The sheer vertical cliffs are composed of rhyolite, a volcanic rock that is the polar opposite of basalt. It doesn't so much flow as explode, in clouds of hot ash that can bury a landscape instantly. The ash can be so hot and so thick when it lands that it is melded into a solid rock more or less instantly. These hardened deposits are called welded tuff. That is the material that forms the remarkable cliffs of Smith Rock State Park. It makes for a climber's paradise.

The cliffs of Smith Rock are part of a caldera, a feature we saw in the last post at Newberry Volcano, but this caldera formed in a far more violent fashion. Because it formed tens of millions of years ago, the shape and form of the caldera has been lost to erosion. We wouldn't see a "modern" (in the geologic sense) caldera until we reached Yellowstone a week down the road.

The stratovolcanoes of the High Cascades provide a backdrop for the tan-colored rhyolite cliffs. The snowcapped peak in the first picture is South Sister (10,358 ft; 3,157 m). Mt. Jefferson (10,497 ft; 3,199 m), the second tallest volcano in Oregon is nicely framed over the balanced boulder in the pictures below and above.

It was hard to turn away, but we had a mountain range to cross. I took one last shot of the steep cliffs, and we trundled into the vans and started to head out to the wilds...of the Portland Freeway system. The archaeologists had something they wanted to see in Vancouver.

We crossed the high ridge on the south flank of Mt. Hood (10,358 ft; 3,157 m), and started down the long hill into town.

Braving the traffic, we crossed the bridge over the very swollen Columbia River into Washington. Mt. Hood loomed in the distance.

Fort Vancouver was a fur trading outpost in the 1840s and later a military installation. An active archaeological dig was taking place as the U.S. Park Service was trying to better understand the arrangement of private housing units adjacent to the fort. Employees of the Hudson Bay Company were provided with some benefits, but they and their families had to grow much of their own food.

The hour was growing late, and we had another hour of driving. As we crossed the Columbia at Astoria, I took a single picture of the ghostly presence of Mt. St. Helens in the far distance. As will be seen, it was the only time we would see the mountain on the trip.

We arrived in camp at Cape Disappointment State Park, on the north side of the mouth of the Columbia River. It was a beautiful place, with campsites only a few hundred feet from the beach. I walked out for a look. The beach was wide and sandy (due to human construction, actually; more tomorrow).

I turned my attention to the cliffs at the northern end. They had an unusual aspect to them. I knew they must be part of the accretionary wedge of the Cascadia Subduction Zone, material scraped off the ocean crust as it dived beneath the North American Continent. I took a closer look.

The cliffs were pillow basalts! Pillow basalts form as basalt pours out onto the ocean floor at divergent boundaries. If convergent boundaries destroy the crust, divergent boundaries are places where new crust is made. They balance each other out in the long run. These basalts traveled thousands of miles at an inch or two a year, before being scraped off to become a part of the coastal complex of rocks.

The bright sunset carried the promise of clear weather. The long-range weather forecasts didn't. That was a problem for another day. The next day, specifically.

I headed back into the forest to enjoy dinner and a relatively warm evening. There were even hot showers! We settled down for a peaceful night. The rain started in the wee hours of the morning.

Picture of the Day - The Airliner Chronicles Part 4

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