Saturday, October 03, 2009

Road trip - part four

In the early 1920's a geologist named J. Harlen Bretz of the University of Chicago proposed that the region in North Central Washington that was to become known as the "Channeled Scablands had actually been eroded by a gigantic flood originating out of Montana 10's of thousands of years ago during the last Great Ice Age.

He was laughed at and ridiculed. For almost 50 years - until images from satellites clearly showed what he had been talking about - he was in his 90's when he received a telegraph saying that his theories had "finally" been accepted.

The lava flows from 25 - 12 million years ago created these layered rocks - creating a solid sea of basalt rock, over 10,000 feet thick in some areas - flowed in some areas over 100 miles long. In places the earth settled, tilting the thick layers, cracking them apart.

During the time of the last ice age, glaciers moved southward from British Columbia into the area now known as Pend Oreille and eastward into Montana. In the process creating ice dams - damming the Columbia, Spokane and Clark Fork River to name a few. These all caused floods but none so great as the Glacial Lake Missoula that formed when the ice plugged the Clark Fork Valley - filling an area about 3,000 miles with about 500 cubic MILES of water (about half the volume of present day Lake Michigan, with a depth of about 2000 feet. The lake that built up behind this ice dam eventually began to overflow, cutting into the ice and the dam was breached sending water through the hills and valleys at over 45 miles & 9-16 cubic miles per hour, roughly equivalent to 10 times the combined flow of ALL the rivers in the world. At first it was thought there was only one or two great floods - in the 1980's a scientist from the US Geological Survey found that there had been about 89 of these great floods.

These floods created channels in the breaks in the lava flows and carried huge boulders out into what is now farmland in Eastern Washington. (some of these boulders, like the ones in our front yard were left there as glacial moraine material. Maybe I should have been a geologist - this stuff is all so interesting to me.

One area in particular is called "Dry Falls" - 3.5 miles of cliffs dropping almost 400 feet - if it was flowing with water today, it would dwarf Niagara Falls. It is now a state park with an area at the bottom of the cliffs called Sun Lakes.

Part of the info I have given you is from a little booklet called "The Channeled Scablands of Eastern Washington - The Geologic Story of the Spokane Flood" by Paul Weiss and William Newman. (the pictures are all mine though)

They say that the roar or the waters that came from the Missoula floods would have been heard hours before the water arrived. There is little evidence that men inhabited this area until about 10,000 years ago, so they would have missed the great floods.

This is the interpretative center at Dry Falls - I never get tired of looking through the displays and trying to imagine how it must have looked when the floods came.

This building was build in the 1960's and somehow got put on the national register of historic buildings -- They really need to replace it because it is not ADA friendly and is too small - but they aren't allowed to because of the historic registry.


Kathy said...

This is SO interesting!

Wrensong Farm said...

I took geology classes at the local community college as something to get credits, but what it got me was so much more! I truly enjoy and am fascinated by it all too!! The Scablands was a memorable field trip that we took....thanks for helping me enjoy them all over again!!

Sharon said...

Gorgeous! Devil's Postpile near Bishop, California is a spectacular display of that cracking - literally into columns.