The Stacks are Odded Against Us! Subduction's Gift in Southern Oregon and Northern California

Sea stacks on Highway 1 near Elk, in Northern California

Sea stacks are isolated rocky islands found along rugged coasts where wave erosion is intense. They form for a variety of reasons (from glaciers in places like Maine, for instance, or from lava flows in Hawaii). If the rocks vary in composition over short distances, some outcrops will be more resistant to erosion and may last longer against the onslaught of the breakers. This is the gift of subduction in areas like Oregon and Northern California. Rocks exposed along the coast tend to include a hodge-podge of ocean-related rocks, including graywacke sandstone, shale, basaltic ocean crust, limestone, chert, and the occasional seamount (seafloor volcano). Some are really tough, and others are easily eroded.

Sea stacks at Point Orford in Oregon

Subduction happens when a thick slab of oceanic crust and upper mantle (the lithosphere) sinks beneath another slab of lithosphere. The crustal material is drawn into the mantle where some of the rock may melt, producing volcanic activity at the surface above. In Oregon and Northern California the oceanic lithosphere is sinking beneath the edge of the North American continent along what is known as the Cascadia Subduction Zone. The volcanoes of the Cascades Range are the very visible evidence of this intense geologic activity.

Subduction zones produce some of the worst of geologic disasters, including massive earthquakes and devastating tsunamis. But the deformation of the Earth's crust also causes the formation of mountains and rugged coast lines that make some of the world's most beautiful scenery. And that is where today's post originates. I had the privilege of spending a few days making my way south along Oregon 101 and Highway 1 in Northern California on my way home from Christmas visits, and we saw a stunning variety of shoreline features including the sea stacks that I am emphasizing today.

Sea stacks near Brookings, Oregon, I think. Anyone recognize them?

The Cascadia Subduction Zone has also collected bits and pieces of continents from elsewhere (called exotic terranes) and mashed them into the edge of the continent. The rocks of the Klamath Mountains in southern Oregon and Northern California originated in this fashion. These metamorphic rocks contribute to the extreme variety of rocks found along the coast.

Restless seas in the morning at Fort Bragg in Northern California

The weather was supremely perfect for viewing the scenery (if not an utter disaster in the making for water-planners; the ongoing drought is the worst ever). There are storms out there somewhere because the waves were quite large at times.

At the mouth of the Navarro River just south of Mendocino in Northern California

This isn't the first time I've used the dumb pun above; I put up a series of sea stack pictures last year when I made my first journey down the Oregon coast in many years. The thing is, these stacks are completely different. There is a lot of very spectacular scenery, and every trip along that route will be a different experience.

Sea arch in a stack at Navarro Beach in Northern California near Mendocino.

Navarro Beach was our last long stop. We actually had to get home at some point after two weeks on the road. It was a truly beautiful day. Happy New Year to all!

Sea stacks at Navarro Beach on the Northern California coast.

Vagabonding across the 39th Parallel: The Birth of the Colorado River and Arboreal Apocalypse

The continuation of our journey vagabonding across the 39th parallel found us descending from the high country of Rocky Mountain National Park on the west side of the Continental Divide. We were looking at views down the long Kawuneeche Valley and the Never Summer Range beyond. There is something special about the Kawuneeche: it is the headwaters of the one of the nation's most important rivers, the Colorado.

The Colorado is no record-breaker in the discharge department. It is dwarfed by rivers like the Ohio, the Columbia, or the Mississippi. The significance of the river lies in its location of the arid southwest. Upon leaving the Colorado Rockies, much of the river's route lies in barren deserts. As such, the river is life to the growing populations of Arizona Nevada and Utah. The river is also directly responsible for some of the nation's most spectacular parklands, including Canyonlands, Arches, and of course the Grand Canyon. Major tributaries to the Colorado have carved Zion, Bryce, Capitol Reef and many other scenic parklands.

The day we visited Kawuneeche, the river was flooding. There had been a combination of a late spring runoff and severe thunderstorms over the previous few days. Roads were covered in water, and meadows were swampy morasses.

We were distracted by the green meadows and high water, but it slowly began to dawn on us that something was very wrong with the forests.

There were dead trees. Everywhere. And not just scattered dead snags; there were whole slopes the color of red rust. It was some kind of arboreal apocalypse. We soon learned that the lodgepole forest had been destroyed by an infestation of bark beetles. They lay their eggs in the bark, and the larvae consume the living tissue under the bark. The trees quickly die.

The beetles in less than a decade have destroyed around 3 million acres of mature lodgepole forests throughout central Colorado. In the past the beetles have been controlled by bitter cold temperatures that kill the larvae over the winter. But for several decades the bitter cold winters haven't happened as global warming has become the new norm. A few years of drought and the trees are defenseless.

The dead forests are a fire hazard, and a physical hazard to homeowners and tourists. The dead snags can topple at any time. Without the root systems, slopes are destabilized and mudslides become a serious hazard. There are a few efforts underway to make use of the dead wood, including energy production and building.

We had been wondering why lots of campsites were available at Timber Creek Campground, when our previous campsites on the east side of the park had been completely filled. The reason was obvious when we pulled in: every tree in the campground had been cut down. There wasn't a bit of shade anywhere. We drove on for another hundred miles and nearly every slope was brown. It was a sad sight.

The forests will grow back, but if the beetles are not controlled in some way, the lodgepole pines will be attacked when they get to a diameter of about five inches. Kind of an uncertain future, and not a good thing for the people in the region who depend on tourism.

Late in the day we had a decision to make. We had no actual plan or route for getting home, and we reached a junction of a road that would take us north to Dinosaur National Monument and the High Uintas of Utah, or a road that would take a more southerly route through the desert country of Arches, Zion and Bryce. We flipped a coin, and headed south...

A Convergence of Wonders, Day 10: Exploring a Real Hot Spot

It was day 10 of our field studies journey through the Pacific Northwest and Northern Rocky Mountains. We had finally arrived at one of the flagship destinations for our trip: Yellowstone National Park! One of the crown jewels of our national park system, home of Old Faithful...we set aside two days to explore the park, and I did something slightly devious to my students. I spent the entire day looking at "not geysers"!

Frankly, I'm not sure any of the students noticed the distinction. That's the thing about Yellowstone; it is so full of wonders and curiosities that it would be a unique landscape to explore even if there were no geysers to be seen at all. We spent our day exploring the northern loop of the park, from Canyon Village and the Grand Canyon of the Yellowstone to Mt. Washburn and then to Mammoth Hot Springs. We stopped in at Norris Geyser Basin at the end of the day, but were distracted by a wolf.

It's funny about furry charismatic animals; they seem to trump the attention of everyone, especially geology students. Our first stop of the day had nothing to do with geology at all, it was to photograph an elk. One cannot travel fast in Yellowstone National Park, because there are constant traffic jams caused by tourons (tourist morons, including ourselves...) looking at bison, elk, bear, moose, beaver, or wolf. I was immune to the effect. I took only ten pictures of this particular elk...

We explored several overlooks at the Grand Canyon of the Yellowstone and Lower Yellowstone Falls. The colorful walls of the canyon are composed of weathered rhyolite just over 500,000 years old. This canyon has been cut very rapidly! 

Standing at the brink of the 308-foot-high Lower Fall of the Yellowstone, one can feel the powerful surge of the water as it disappears over edge. It's not hard to believe that such a deep canyon could be carved by a river like this.

The most astounding story to be learned at Yellowstone was never envisioned by those who established Yellowstone as our first national park in 1873 (Yosemite was set aside nine years earlier, but as a state park). We drove to the high ridge near Dunraven Pass and Mt. Washburn to have a look around.

There is a fable about several blind men who were touching an elephant and disagreeing about its nature, whether it was like a rope (the tail), a snake (the trunk), or a tree (the leg). Yellowstone's most striking feature was so big that it was decades before geologists recognized it for what it was: a vast caldera, the site of three of the largest volcanic eruptions to ever hit the North American Continent in recent geologic time (2.1 million, 1.3 million, and 640,000 years before present).

How big is the caldera? The snowcapped mountain in the distance in the picture below is Mt. Sheridan. We were standing on the side of  Mt. Washburn; there is a forty mile gap between the two. The mountain ridge that connected the two peaks sank into the caldera during a single massive eruption that put 600 cubic miles of ash into the atmosphere. The ash spread for thousands of miles. A repeat eruption would be devastating to civilization (despite what the television tells you, such eruptions are not imminent, nor are they overdue; we would see signs of caldera unrest dozens, if not hundreds of years beforehand). The source of these eruptions is thought to be a mantle hot spot, although there are several alternate interpretations.

Volcanism has been influencing events in the Yellowstone region for a long time. In early Cenozoic time, around 50 million years ago, the region was rocked by numerous eruptions that produced volcanic mudflows (lahars) that overwhelmed forests of sequoia/redwood trees (You thought they were found only in California didn't you? They were once much more widespread). Each time a forest was destroyed and buried, a new forest would grow in the sediments. That forest was destroyed in turn, and over time dozens of layers containing petrified logs accumulated. These forests are generally hard to access by road or trail, but one solitary upright trunk can be seen in the north part of the park. There used to be three here, but souvenir collectors carted off the others, which explains the prison in which the trunk resides.

We moved on down to Mammoth Hot Springs (with a few bear diversions), and took a look at the strange edifice of calcium carbonate. Most of the hot springs and geysers of Yellowstone do not produce massive mineral deposits, but they happened here, outside the boundaries of the caldera. Most of the water emerging from geothermal features in the park is charged with silica, but at Mammoth, the water has passed along faults that traversed Paleozoic limestones. The acidic waters dissolved the calcite making up the limestone, and when the waters emerged here, the calcite came out of solution.

The hot springs are constantly growing and changing location, so the deposits never look quite the same. Heat-tolerant bacteria provide a splash of color to the otherwise snow-white rock.

Spelunkers (cavers) will recognize many of the deposits, as they are similar to flowstone features found in many limestone caverns, especially the rimstone pools seen in the pictures below. Exploring Mammoth Hot Springs is kind of like exploring an inside-out cavern...

 The rimstone pools were especially photogenic...

There were several killdeers strolling across the pools...

We drove on in the late afternoon to Norris Geyser Basin, but I didn't get any pictures. We were distracted by the whole charismatic mammal thing anyway, the subject this time being a Canis lupus enjoying a meal in a meadow north of Norris.

You can see the whole wolf drama in this post.

We were done with another day...tomorrow would include the famous geysers (maybe), and Grand Teton National Park.

I've been posting regularly for the last ten days, but I am hitting the road again tomorrow, so the next few posts will be at unpredictable intervals, as web access will be tricky. Take care, all!