What Could be Worse than the Crater Lake Eruption? A look at Smith Rock State Park in Oregon

Standing on the rim of the Crater Lake caldera, as we did in our last post, it is hard to imagine the scale of the catastrophe. In that event just 7,700 years ago, 15 cubic miles of ash was blown into the atmosphere, covering much of western North America with volcanic dust. A similar-sized event at Tambora in 1815 caused the deaths directly of tens of thousands, and worldwide, possibly hundreds of thousands (from climate-induced famine). How could it be any worse? The answer is found not all that far away. On our Pacific Northwest journey last June, we stopped at Smith Rock State Park between the towns of Bend and Madras in Oregon. The two sites are about 120 miles apart.

Smith Rock State Park is small as such things go, only about a square mile, but the setting, as can be seen in these pictures, is rather spectacular. The 600 foot high tan-colored cliffs are popular with climbers, while a flat plateau (on the right side in the picture above) provides flatlands for parking and camping. The Crooked River flows through the park. How did these odd rocks come about?

The flat plateau is perhaps the easiest to explain. Newberry Crater is a massive basaltic shield volcano located about forty miles to the south. About 400,000 years ago, a basalt flow emanating from Newberry flowed north until it was stopped by the cliffs of Smith Rock. The Crooked River then eroded a channel between the contrasting rock types.

It is the tan cliffs that really tell the story of catastrophe. It was a disaster so huge that its dimensions were not recognized until fairly recent times. The cliffs of Smith Rock are part of the northwest corner of the Crooked River caldera, a sunken crater that is 25 miles long and 15 miles wide. Crater Lake's eruption produced around 15 cubic miles of ash. The Crooked River eruption produced around 200 cubic miles. Imagine a dozen Crater Lake eruptions happening at once and you start to get an idea. The eruption rivals some of the worst of the disasters at Yellowstone or Long Valley in eastern California. The only saving grace here is that the eruption took place around 29.5 million years ago. The magma chambers that fed the event have long since cooled.

As the hot ash landed, some parts remelted and cooled to form solid welded tuff. Other parts hardened as hot gases and steam coursed through gaps and openings called fumaroles. The cooling mass contracted and fractured into numerous joints. Differential erosion produced the various pinnacles and spires seen at the park.

Modern human beings have never experienced an eruption of this magnitude. The last one of this size worldwide, at Toba in Indonesia about 75,000 years ago, may have almost done in the human race (a controversial idea, but plausible). It involved around 470 cubic miles of ash.

I notice that Smith Rock sits at the south edge of totality during the coming Solar eclipse. If you are lucky enough to get to the park as a setting for this once in a lifetime event, I hope you'll spend a bit of time pondering the incredible history of these rocks as well.

For some detailed information about the history of the Crooked River Caldera, check this link.

A Convergence of Wonders: A Compilation

The trip I called the Convergence of Wonders was a combined geology and archaeology course that we conducted on June 15-30, 2011, in which we explored the Pacific Northwest and Northern Rocky Mountains. Our students and volunteers traveled more than 4,500 miles through regions that have been influenced by convergence along the Cascadia and related subduction zones, as well as a hot spot and continental divergence. Each day revealed stunning geological features and insights into the human occupation of the region over the last 13,000 years or more. This is a compilation of all of the blog entries I posted about the trip.



"Journeys in the Pacific Northwest" was the introductory post about the series, and provided some background about why we did the trip we did, and what our goals were. 





"Journeys in the Pacific Northwest, Day 1" was the story of the trip from home to our first camp at Lava Beds National Monument on the night of the full moon. En route, we explored the flanks of Mt. Shasta, the largest stratovolcano in the Cascades, and found out that a record snowpack and late spring was going to be a problem on this trip.

"Day 2, Lava Beds and Newberry Caldera" includes our exploration of Lava Beds National Monument, including the extensive lava tube system, an incredible panel of petroglyphs, and the site of the last war between the federal government and Native Americans in California. Late in the day, we visited an obsidian dome in Newberry caldera.

"Day 3, Crossing the Subduction Zone" chronicled our passage across the Cascades to the Washington coast at the mouth of the Columbia River at Cape Disappointment State Park. Smith Rock State Park in Oregon was an incredibly scenic view into the heart of a rhyolite caldera eruption, and our day ended looking pillow basalts from the floor of the Pacific Ocean floor. In between, we checked out an excavation taking place at Fort Vancouver.

"Day 4: Cape Disappointment and Real Disappointments" was the story of weather-related disappointments. The skies opened up throughout the day, including along the flanks of Mt. St. Helens, which was to be the centerpiece of our exploration. The mountain remained invisible in the clouds. The sun emerged, of course, but not until we were far beyond the crest of the Cascades and almost to our camp in Yakima.

"Day 5: In the Land of the Great Flood" was a narrative of our passage across the wastelands produced by a series of catastrophic floods that defy human imagination. At Dry Falls, we looked at canyons (the coulees) that were carved in a few days or weeks of remarkable "river" flows hundreds of feet deep. We also had a chance to see the Wenas Creek Mammoth at Central Washington University.

"Day 6: In the Land of the Great Draining" was an exploration of the lands where the floodwaters originated: glacial Lake Missoula. We traversed a barren valley (the Camas Prairie) where ripplemarks thirty feet high convinced many geologists of the occurrence of the Spokane Floods. We arrived in beautiful Glacier National Park at the end of the day, and were greeted with an incredible rainbow.

"Day 7: Of Time and Pressure in Glacier National Park" found us at the Canadian border where we started an exploration of Glacier National Park, at least the parts that were not still snowbound. We checked out the Lewis Overthrust, and examined the Proterozoic sedimentary rocks that make up much of the park.

"Day 8: Of Time, Pressure, and the Plain Truth" found us out on the Great Plains east of Glacier. We toured the Museum of the Plains Indians in Browning, and worked our way past numerous thrust sheets in Sun Canyon, where convergence pushed numerous fault slices over one another. We also checked out some exhibits on some of the most famous discoveries concerning dinosaurs at Choteau, Montana.

"Day 9: Into the Depths of the Crust, and of Time" discusses one of the most spectacular roads in America, the Beartooth Highway from Red Lodge to Yellowstone National Park. We also checked out the Stillwater Mine, where platinum and other rare minerals are produced. The outcrops we were traversing including some of the most ancient rocks on the continent.

"Day 10: Explorations of a Real Hot Spot" was just that...a tour of Yellowstone National Park, one of the crown jewels of the National Park System. We explored Yellowstone Falls, the Grand Canyon of the Yellowstone, Mammoth Hot Springs, and Norris Geyser Basin. The highlight for many of us was the witnessing of a wolf competing with a raven at a kill site.

"Day 11: The Orange Steam is OK, but the Blue Stuff Will Kill You" was a further exploration of Yellowstone, with visits to Grand Prismatic Hot Spring, and the famous geysers in Upper Basin (yeah, Old Faithful was spouting off, but I was watching Beehive). We ended the day in Grand Teton National Park.

"Day 12: A Richness of Geological Drama at Grand Teton (and Pelicans)" was a beautiful day of exploration in the Grand Tetons. We also checked out the Gros Ventre Slide, one of the most famous slope failures in the United States.

"Day 13: Hidden Treasures and Hazards on the Road in Western Wyoming" saw us beginning the long journey home. We checked out the Game Creek Archaeological Site and Fossil Butte National Monument, and saw a lot of sagebrush as we made our way south into Utah...

"Day 14: Treasures Discovered and Lost in Nine Mile Canyon" chronicles an expedition through seventy-mile long Nine Mile Canyon, a showcase of Fremont Culture artwork and archaeological sites. The canyon is also a site of controversy, as heavy industry is mining natural gas in the area, with profound effects in the canyon itself. Later in the day, we saw the Dinosaur Museum in Price, and ended the day searching for Topaz crystals in the western Utah desert.

"Day 15: We Go Underground in Great Basin" saw us making a 500 mile journey across the Basin and Range Province, with a stop at Great Basin National Park for a tour of Lehman Cave, and a stop at Garnet Hill, for, eh, garnets. A motorcycle accident caused us to arrive in a spooky camp at 11:00 PM.

"Day 16: Our Home Mountains, Giant Swimming Reptiles, and a Bunny" was our last day on the road. We checked out the bizarre Mesozoic creatures at Berlin-Ichthyosaur State Park in Nevada, Mono Lake in eastern California, and Yosemite National Park in our backyard before arriving at the end our journey.

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.