The Surprising Forces That Shaped Lake Chelan

Approximately 15,000 years ago, a significant portion of the Northwest was covered by a Canadian ice sheet.

The same ice sheet that covered and carved up the Puget Sound region moved down and covered Lake Chelan with 2,000 feet of ice. The Canada Ice Sheet also created Lake Pend Oreille in Idaho.

It was two opposing ice fingers that made Chelan so deep.

A geologist named Jon Riedel has evidence that Rainy Pass, a low point in the North Cascades, allowed an arm of the Canadian Ice Sheet to flow over Stehekin and into what is now known as Lake Chelan. 

This ice finger was not the only piece of ice responsible for carving Lake Chelan.

It was met head-on by another arm of the Canada Ice Sheet, the “Okanogan Ice Sheet” that flowed from the East and up the lake. 

'These two independent arms of the continental ice sheet met up head-on over Lake Chelan and had a digging contest essentially. Who could dig deeper, to make this hole that's below sea level.”' -CWU Professor Nick Zenter

 

Where is Lake Chelan the deepest? 

The deepest part of Lake Chelan, at 1,459 feet, is located just past the “Manson Bend” in the lake.

And WHY is Lake Chelan so deep there?

Lake Chelan’s bed - just past the bend - is made of a softer material called shist. 

Just past the "Manson Bend" is where the two arms of the Canada Ice Sheet met and pushed against each other, resulting in ice digging deep down into the softer rock. 

'Schist is rich in flaky and soft sheet silicate minerals, which makes it structurally weaker than gneiss' -Sandatlas.org

Nick Zentner delves in-depth to explain the deep carving of Lake Chelan and explains the great Entiat earthquake of 1872.

There is evidence that a significant earthquake occurs near Entiat every 200 years.

Oh no, the Entiat Earthquake in Entiat is due again soon.

We are slightly less than 50 years from yet another major earthquake in North Central Washington.