On the Trail of the Pacific Northwest’s Ice Age Floods


A rendering of an Ice Age flood (image usage permission granted by Stev Ominski)

One of the biggest surprises about Northwest natural history is that there were many catastrophic floods during recent geological times that dramatically altered the landscape of Washington state. Almost half the state was inundated. This hypothesis was first put forward by geologist J Harlan Bretz in the 1920s.

These floods are thought to have swept through the state many times during periodic ice ages. During the last ice age, a lobe of a Canadian glacier blocked the Clark Fork River drainage in Idaho, causing glacial meltwater to fill up the valleys of the Mission, Bitteroot and Rattlesnake Mountains to form Glacial Lake Missoula, estimated to have been 3,000 square miles. High above Missoula, along the  mountain slopes, there are strandlines of many prehistoric lakes. More than once, when the water level became high enough, the ice dam would be breached and let loose 500 cubic miles of water in 48 hours, a cataclysmic megaflood that drained to the southwest into eastern Washington, down through the Columbia gorge, into parts of western Oregon, even extending as far south as Eugene, and out to the Pacific Ocean via the Columbia River. At one time, present-day Portland was buried under 400ft of water. It is estimated that the flow rate was ten times greater than all of the world’s rivers combined. The onrushing deluge carried with it not only unimaginable amounts of water and debris but enormous boulders, some rafted on icebergs over hundreds of miles before being deposited (glacial erratics). The Willamette Valley in Oregon has erratics up to 40 tons. These repeated inundations stripped off the topsoils of eastern Washington to lay bare the hard basaltic layers underneath (from previous volcanic lava flows as early as 17 million years ago) that earned this area its name, the  channeled scablands (coined by Bretz). To this day, after many thousands of years, you can still see evidence of the flood(s).

The scablands would not be as spectacular if not for the basalt layers. One common form that appears in the Northwest is columnar basalt, vertical cracks forged in the basalt layers as they cooled very slowly. Less resistant to erosion is basalt entablature, usually on top of  columnar basalt, that has cooled more rapidly and therefore don’t readily form clean vertical cracks but show a more random fracture pattern. When monstrous floods attack these layers, columnar basalt can more easily be plucked away, leaving behind steep, vertical channels in the landscape, called coulees. Most coulees are dry, unlike canyons that still have rivers flowing in them.

Example of columnar and entablature basalt, ingredients for creating the flood landscape of the channeled scablands

My wife and I set out on a road trip to see firsthand some of the spectacular evidence that these floods left behind. I picked out a few important sites that we could fit into a three-day trip. Going by car is a great way to visit these places, especially with the help of references such as Bruce Bjornstad’s classic book as a guide. This book

Our first stop was an overlook just outside Quincy. A short half-mile hike to the edge of Babcock Ridge gave us a stunning view of the resort of Crescent Bar over 600ft below and giant flood-produced current ripples on a bar across the Columbia River. These ripples are gigantic in scale, about 20-50ft high and spaced over 300ft apart, estimated to have been submerged under 600ft of water. At that height, the waters overtopped portions of the ridge that we were standing on, carving out the gigantic Potholes Coulee just to the south.

Giant current ripples on West Bar along Columbia River. (Note water vessel for scale)

Another phenomenon that fast-moving water creates are potholes. High-energy tornadoes of water (or kolks, as they are called) tore out huge holes in the bedrock, sometimes more than a mile wide. Some are now lakes and ponds, but most of them are dry. There are many examples of this, including the gigantic one we saw north of the Frog Lake trailhead on Morgan Lake Road in an area called the Drumheller Channels and the lakes below Dry Falls.

A kolk created this giant pothole in the Drumheller Channels. (Note that I’m in the center of the photo which only shows a portion of the pothole.)

Drumheller Channels are an amazing network of interconnected, braided channels that were sculpted out of the earth by the deluges from the northeast. Below is a panorama that I spliced together from seven photos taken along our drive on Morgan Lake Road.

A glimpse of the Drumheller Channels from Morgan Lake Road (click to enlarge)

As dramatic as the landscape looked from the road, we just couldn’t visualize what this area looked like from above. With the help of Google Earth, it can clearly be seen. This area was unique enough that it was designated a National Natural Landmark by the National Park Service.

Drumheller Channels looking northwest toward Potholes Reservoir (Google Earth)

Along the northern shore of Lake Lenore are a series of caves that were carved out by the swirling flood waters, plucking out the looser columnar basalt more easily than the more resistant entablature above it. You can see them as you’re driving along Hwy 17. A turnoff for the attraction leads to a parking lot where the trailhead is located. Beyond the stone staircase up a short distance, the trail divides to the left and right. Some of the caves were large enough for prehistoric people to have used as shelters.

One of the many flood-cut caves along Lake Lenore

Further, just before Coulee City, is Sun Lakes-Dry Falls State Park, an area used for recreation and a showcase for observing the handiwork of ancient floods. Spanning 3.5 miles wide and averaging 400ft in vertical drop, Dry Falls is the remnant of the largest falls that the world has ever seen, ten times the size of Niagara Falls, but now a dry cataract. You can try to envision this cataclysmic spectacle from the Dry Falls Interpretive Center on Hwy 17, two miles north of the main park entrance. (Un)luckily for us, the center was closed for the entire day due to staff meetings. But, the overlook is open year-round (weather permitting). From here, you can gaze at the immense cataract and the plunge pools, now lakes and ponds, that the waterfalls created.

Satellite view of Dry Falls cataracts  looking south (Google Earth)

Dry Falls panorama from Interpretive Center overlook (click to enlarge)

As we drove past Ephrata toward Moses Lake on Hwy 17, we couldn’t help but notice the vast flood plain littered with boulders. When the flood waters broke free from the Grand Coulee, they spread out into the Quincy Valley and deposited these boulders knocked free from the Grand Coulee and sources upstream, some as high as 60ft. This area is known as the Ephrata Fan, an expansion flood bar, where there is little productive farming.

Glacial erratics along Hwy 17 between Ephrata and Moses Lake (Google)

While almost all flood-cut waterfalls in the channeled scablands are now dry cataracts, there is one that remains, a whisper of its former self, but spectacular nonetheless. Palouse Falls flows year-round, but its most impressive displays are during spring melt when the volume is greatest. At the foot of the falls is a large plunge pool. The falls are part of the Palouse River system, which continues through the breathtaking Palouse River canyon downstream to join the Snake River. Unlike typical canyons, these coulees were sheared by the ice age floods.

The best place to see it is at Palouse Falls State Park, accessed by a spur road from Hwy 261, 17 miles from Washtucna. We enjoyed a picnic lunch here (there are nice picnic tables) and hiked a trail that hugged the edge of the coulee, including one that led to a very narrow ridge directly above the pinnacles to the left of the falls.

Palouse Falls used to tumble over the entire gap but is now a shadow of its former self.

Beyond Palouse Falls lies the Palouse River canyon. Note the vertical walls typical of flood-sculpted coulees.

This illustration by artist Stev Ominski dramatizes what the event probably looked like.

A rendering of the flood through Palouse River Canyon (image usage permission granted by Stev Ominski)

Interestingly, ninety percent of Washington’s vineyards are planted in soil deposited by or as a consequence of the ice age floods. Almost all the silts and minerals that used to cover the scablands got stripped away and laid down in the Columbia and Walla Walla valleys where the state’s finest vineyards are located. The Willamette Valley in Oregon, known for its pinot noir, also has soil similar to that from Lake Lewis, the temporary 1,200-foot flood-produced backwater lake that rose behind Wallula Gap in eastern Washington and covered the Tri-Cities area (Pasco, Richland and Kennewick).

Only three days long, our road trip was certainly not comprehensive enough to see even a fraction of the geological evidence of a megaflood. But, with a new understanding of what took place, I will never look at eastern Washington with the same eyes as before. It was worthwhile and humbling to take the trip.

Update (8-4-15): Lying between McMinnville and Sheridan near Oregon’s Highway 18 are glacial erratics that were left behind by one of the Missoula floods. Erratic Rock State Natural Site showcases a 36-ton argillite specimen that is presumed to have been encased in an iceberg that got rafted by a flood and deposited here when the water receded. It is the largest erratic in Oregon. What makes this particular set of rocks so unusual is that they came from Canada, the only ones known to have traveled beyond our neighbor’s borders.

erratic rock

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City of Rocks State Park (Faywood, NM)


Our final night of camping on this road trip was spent at City of Rocks State Park, north of Deming in the middle of the Chihuahuan desert, a unique, surreally beautiful area where every campsite is nestled among huge boulders.

City of Rocks features a wide field of boulders created 35 million years ago when a volcanic eruption from the Emory Caldera rained down tuff that hardened and was eroded by wind and water over millions of years. Some of these rocks are 40 feet high and are quite beautiful, ignimbrites of pinks, blue-grays, and browns, and strewn over 1,200 acres in the middle of the Mimbres valley, an odd sight in an otherwise flat and featureless terrain. Some of these upright megaliths reminded me of Stonehenge, but mostly they are randomly scattered, sometimes forming lanes between them that suggest urban pathways. The park also includes an astronomical observatory (one of two in the New Mexico state park system) that has a 14″ telescope. Keeping with the astronomical theme, the various sections of the park, arranged in loops, are named after constellations.

At night, without light pollution, dark-night-sky viewing is possible. On the night of our stay, the skies were clear; we might’ve seen the Milky Way as we did at Chaco Canyon if it weren’t for a bright full moon. We heard coyotes howling overnight and in the early morning.

Among the many desert plants here, the ocotillo stood out as the most unusual, tall and cactus-like with near vertical stems branching at ground-level and spiny appendages all along them. For most of the year, they can appear to be dead, but we were fortunate to have seen them fully leafed out and topped with crimson flowers, a direct result of prior rains.

Too bad we were in a rush to get to the Grand Canyon. This is a campground worthy of a longer stay.

City of Rocks State Park
Faywood, NM
575.536.2800
 

Camping at Leasburg Dam State Park (Las Cruces, NM)


The wind and rain clouds were rolling in over Las Cruces as we arrived in the late afternoon. Though we’d already canceled camp sites on this trip because of weather, we decided to pitch camp anyway and hope for the best. After dinner, we headed straight to our next camping site at Leasburg Dam State Park, outside Las Cruces.

Each campsite has a concrete pad so we had no problem setting up. As we were going to be here for a single night, we attached the tent to the back of the Subaru, extending the living space and making it considerably easier to get to things if the weather got bad.

Our tent conveniently straps to the back of the car

Our tent conveniently straps to the back of the car

The attached tent extends the living space

The attached tent extends the living space

That night, a hellacious storm dumped rain with heavy wind. It was so gusty that the tent made flapping noises all night. Furthermore, thunder boomed overhead and lightning crackled and lit up the tent. But the topper was the train that was some distance away but sounded as if the tracks were right next to our tent, an illusion of the night air. The conductor also saw fit to toot the whistle every time the train roared by. It was by far the most restless sleep we ever had camping.

The following morning, all was quiet though ominous storm clouds still hovered overhead. It was nonetheless a spectacular canopy just as the sun was rising.

Cloud cover the morning after a thunderstorm

Cloud cover the morning after a thunderstorm

In the morning, we packed up our wet tent and, based on a weather prediction of more rain, decided to cancel the reservation we had for the next two nights at a campsite in Alamogordo.

Smith Rock State Park (Terrebonne, OR)


North of Redmond, rock climbers flock to Smith Rock State Park to scale the spectacular vertical walls of hardened volcanic tuff. We made a brief stop here on the way home, even though I was under the weather with chills and body aches. Probably against better judgment, I decided we should take the brief hike down to the Crooked River and watch some rock climbers in action. There are other hiking trails, one of which leads to the top of the rocks, but this will be reserved for another day.

Smith Rock attracts rock climbers from around the world

Smith Rock attracts rock climbers from around the world (note climbers at the base)

These rocks were formed when volcanic eruptions blanketed the area over a half million years ago in a half-mile thickness of ash that eventually welded, then eroded. Rhyolite dykes with their jagged edges are also found in the park, especially dramatic when they intrude into the tuff.

Rhyolite dykes make their appearance throughout the park

Rhyolite dykes make their appearance throughout the park

It’s easy to lose sight of the fact that there has been a lot of cataclysmic volcanic activity all around us in the distant past. While this fact is not difficult to see where there are fields of hardened lava, such as around Bend only a few miles from here or the basalt layers all over eastern Oregon and Washington, Smith Rock tells the story in a different way, no less spectacular.

Fern Canyon (Prairie Creek Redwoods State Park, CA)


Steven Spielberg saw its primeval potential for Jurassic Park 2, the backdrop for the T. Rex chase scene. Fern Canyon is an impossibly verdant gorge, carved out millions of years ago by a retreating sea, its vertical walls literally covered with walls of ferns, five species of them, and mosses. Water seems to seep out of the sides throughout the year, providing a very moist environment for these plants to flourish. The stream that cuts through the canyon sometimes gets high enough that wooden planks must be placed down at strategic points to prevent hikers from getting their shoes too wet. It’s worth the diversion off Hwy 101 to take this short but spectacular 1-mile hike.

Five-fingered Fern, one of 5 species in Fern Canyon

Patrick’s Point State Park


Miles off the coast, the Farallon Plate is subducting under the North American Plate

There is no better evidence of the powerful forces of plate subduction than the shoreline of Patrick’s Point State Park. The Farallon Plate is diving under the North American plate slowly, leaving behind good examples of broken and folded coastline, including some impressive examples of basalt outcroppings out at sea. There is a fault that runs through the center of the park.

Studded with forests of evergreen and alders, carpeted with many wildflowers, the area belies the natural forces at work. On the trails we took, lupines and irises were in bloom. At the edge of the forest are sheer cliffs that overlook the beaches and ocean. At one overlook, we could see puffins and auks, nesting along the cliff sides and diving into the sea. One trail led to a dramatic vista of the ocean.

Lupines along the trail

Douglas iris

Nu’uanu Pali State Wayside Park


Nu’uanu Pali Wayside overlooks windward Oahu

A spectacular way to get from Honolulu to windward Oahu is State Hwy 61 (Pali Highway) through a pass over the Ko’olau mountain range. There is an overlook near the ridge where you can get a sweeping view of the northeastern side of Oahu.

The winds are strong up here, sometimes so strong that you can literally lean into it. The trade winds from the windward side blow through the pass and, by virtue of the Venturi effect, pick up speed and strength on its way toward Honolulu.

The bloodiest battle in Hawaiian history was also fought here when in 1795 Kamehameha’s forces landed on Oahu from Hawaii and conquered Kalanikupule near this lookout. Soon afterward, Kamehameha became the first king of the Hawaiian Islands.