Hello Young People.
Entrenched Meander.
This is the Yakima River just south of Ellensburg,
Washington.
Meanders are a feature of old age.
These sweeping curves of the river.
As rivers age they develop more and more exaggerated
meanders.
We know this by flying over the Mississippi
River system.
And we see all stages of meander development
back there.
Eventually, the meander become so exaggerated
that that curve is abandoned and an oxbow
lake is formed.
And the channel becomes straight again.
We can only develop these curves when an area
is flat like back east at the Mississippi.
And here we've got these exaggerated curves
as well which means central Washington used
to be flat.
But there's a twist.
This place isn't flat anymore.
This is a deep canyon system.
So to understand that twist, how 'bout we
get up on that rim and get a big picture view
of the Yakima River Canyon.
Let's go up there.
High up above the Yakima River on the rim
of the canyon looking down.
There's one of our meanders.
We know about meanders.
The meanders got established when the area
was flat.
A subtle curve becoming a more exaggerated
curve.
But then we froze the position of this meander,
and we entrenched it.
Entrenched meanders tell us that the land
is lifting against the river.
The river wasn't up here and was cut down.
We're sure that the river has been down there
for millions of years and the land has been
lifting against the meander - against the
river.
The river's been cutting, matching an uplift
rate of the bedrock.
Basalt layer after basalt layer exposing themselves
on the way up.
The future of this meander is not more exaggerated
meander.
Development of an oxbow lake.
Instead, the future of this curve is more
cutting.
Because the uplift continues here in central
Washington.
Entrenched Meanders.
Just south of Ellensburg, Washington.
