Thursday, March 19, 2015

If this is Thursday it must be postcards, 186

Dry Falls, central Washington

The used card pictured above shows Dry Falls in central Washington State as photographed by C. B. Ellis and published by the Ellis Post Card Company of Arlington, Washington, mailed in 1991.  During the last Ice Age water cascaded over these walls, five times the width of Niagara Falls, in huge torrents making it larger than any other known falls and thought to have been the greatest waterfall that ever existed.  Using models it has been determined that the water would have been traveling 65 miles per hour through the Upper Grand Coulee and over this 400 foot rock face.  The estimated flow is ten times the current flow of all the rivers in the world combined.  Today Dry Falls is a 3.5 mile long “scalloped precipice” at the head of the Lower Grand Coulee.

Glaciers moved south across North America nearly 20,000 years ago causing an ice sheet that made a natural dam flooding a significant part of Montana forming a gigantic lake called Lake Missoula.  During the same time period another ice dam formed on the Columbia River making Glacial Lake Columbia.  Eventually Lake Missoula rose so high that the dam gave way causing a cataclysmic flood spilling into Glacial Lake Columbia and then down the Grand Coulee.  It is thought that this flooding probably happened dozens of times during the years of the last Ice Age.  The “sudden flood put parts of Idaho, Washington and Oregon under hundreds of feet of water in just a few days.” 

When the ice melted at the end of the Ice Age the river returned to its normal levels and left Grand Coulee and these falls dry. 

There is an Interpretive Center at Dry Falls in the Sun Lakes-Dry Falls State Park located near the town of Coulee City.  A Discover Pass is required for parking but admission free. 

Additional information can be found here:

No comments:

Post a Comment