Hello Young People.
Coulees.
What is a coulee?
Coulees are very unusual valleys.
Their shapes are unusual.
Valleys around the world are V-shaped with
rivers carving slowly through time.
U-shaped valleys around the world.
Alpine glacial ice flowing out of mountains
and carving the landscape.
But these coulees are very different.
They are box-shaped valleys.
With flat valley floors, vertical walls, and
no rivers flowing through the bottom of the
valleys.
Ice Age floods between 28,000 and 14,000 years
ago took lots of bedrock away leaving these
box-shaped valleys known as coulees.
There's a lot of rock missing here.
That's the coulee!
Did the Ice Age Floods really take all of
that rock away?
They did.
The bedrock is the key.
So why did the Ice Age Floods dig into the
bedrock and haul so much rock away?
Why didn't the water just skim over the top
of the bedrock?
The answer is looking at the structure in
the bedrock.
Do you see this climber right over here?
This guy's climbing right up a beautiful column.
With cracks between the columns.
This is basalt.
A lava flow rock that came in one lava flow
at a time.
And when the lava cooled, it cracked.
Vertical fractures and horizontal fractures.
Some layers more stubborn to erosion than
others.
So let's bring the Ice Age Floods in.
Pick up columns.
One by one.
Haul them off.
The bedrock is precut and ready to be hauled
off by the floods.
Coulees of central Washington!
