Monday, May 1, 2017

Dry Falls (Largest River on Earth EVER)

We were driving to go see Grand Coulee Dam on the Columbia River in Washington State, and this is how the scenery looked:

It's quite a deep canyon - but the Columbia River isn't in the canyon!?  I didn't quite understand what we were looking at.

The geology is made of multiple layers of basalt, laid down from eruptions over millions of years.

Big canyons....I never knew these even existed in Washington State.

Then we got to a place called Dry Falls, and I finally understood what we were looking at.  Dry Falls was the largest water fall the world has ever known, and was in the largest river the world has ever seen.  This occurred during the last ice age, when a 1/2 mile + high glacier in Idaho made an ice dam across the Clark Fork River, forming a giant lake called Glacial Lake Missoula, because it was largely in Montana around what's now the town of Missoula.  Periodically, the ice dam would fail, releasing all the water from the lake.  Scientists estimate that the flood waters flowed at 65 mph over the falls, which are about five times as wide as Niagara Falls.  They think that the flow was about 10 times the total current flow of all the worlds rivers!  500 cubic miles of water, about half the volume of current Lake Michigan would flow through in a mater of days and weeks, eroding and scouring the landscape.  If  you've been reading the blog, you'll remember some discussion about this when we visited the Columbia River and the Bridge of the Gods post.

According to a Wikipedia entry, scientists have found evidence of at least 25 of the flood events, and estimate the river flow to have been 95,000,000 cfs or 2.7 million m^3/s.   For comparison, I just looked up the current flow of the Westfield River, which is recorded by a gauging station near the Walmart on Hwy 20.  Right now, the river is flowing at 936 cubic feet per second, or about 26 m^3/s, or about 100,000 times less water.

Here's a map showing the inundated areas in brown.  You can see Astoria and the Columbia River Gorge, which you might recognize from earlier posts.

An artists impression of what it might have looked like.  Realize though, that the waterfall is about 3.5 miles across and 400 feet high.  One kiosk estimated the water was about 300 feet deep pouring over the lip.  The picture we took above is from the left side of this painting.  Some of the information we read said that the waterfall eroded its way upstream about 15 miles during the events, which is what created the giant Coulees we were driving through and camping at.

Another picture of the eroded area and a plunge pool.

One of the interesting stories about this is the scientific process of understanding the event.  The first geologist to propose the giant flood, Harlen Bretz, was largely ridiculed by the scientific community. He spent his lifetime collecting data and eventually the scientific community has come to accept the theory, with the Geological Society of America eventually awarding him their highest honor, the Penrose Medal. There's more info on that in the Wikipedia entry above, and the links to Harlen Bretz's entry.

We camped at a place called Steamboat Rock State Park, in Washington.  This beautiful waterfall is flowing over the edge of the Coulee.  A Coulee is a gully, ravine, or valley where water flows or flowed.  It's a french term, mostly only used out west.

Here's a picture of Steamboat Rock from the campground.  The rock is about 800 feet higher than the present water level, but was submerged during some of the floods.

We decided to try to hike up.  If you look really, really carefully, you can see a couple hikers about a half-mile away on the diagonal seam on the scree (loose rock) just above the sage in the picture.

The trail gains about 650 feet in altitude. Unfortunately, my dog Patch, who is 14 years old and has 3 legs, couldn't make it up the steep slope.  So, Karin volunteered to stay at the bottom with him, and Sophie and I hiked on.  Realize that this is the rainy season in Central and Eastern Washington, when the world looks its best.  There were beautiful wildflowers....

and cool geologic formations from the basalt....

And finally, we made it to the top.  This is the view down the Grand Coulee.

And up.  Imagine this full of water.  Apparently, the head (upstream edge) of Steamboat Rock has a very hard layer of granite that didn't erode during the massive flooding events.  This was the Columbia River's temporary river bed during periods of glaciation, and it would return to its current location during periods when the glacier was gone.  I kind of expected the top to be different, with unicorns or something, but actually it looked just like the flat, dry land you see in the rest of Central and Eastern Washington.  The scale is hard to come to grips with, but when you're in the Coulee, you really are in a ditch, cut through a relatively flat place.  It's just BIG.

Berkshire Mountain Poodles can hold their own on any mountain, anywhere.

An erratic left on top by the high flows.  Again, imagine water powerful enough to move this van-sized rock, and to leave it and it's brothers strewn all about.

Here's Mrs. Dr. V and Patch waiting at the bottom, taken from about halfway sliding down that scree slope.

and the obligatory Sunset at Steamboat Rock, in the Grand Coulee...

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