Sheer Drops, Sculpted Islands and Cliff Caves
[201.3 MM 96 State 17 S]
Turn left into the Dry Falls Museum and Overlook.
Dry Falls is the western part of the 3-½ mile long cataract (falls). The drop is 380 feet here and you can see water in the plunge pools carved by the falling floodwaters. By comparison Niagara Falls is 1 mile wide with a drop of 165 feet. Imagine a waterfall twice as high and 3 times as wide as Niagra Falls seen in this photo at right.
|"This is an awesome sight and much too big to take in all at once. From your left shoulder over to your right the panorama is breathtaking in its width and depth. The Dry Falls pictures on this page are only about a quarter of the whole scene." [Draggoo]|
(Jay Cousins Photo)
A note about the Interpretive Center from The Dry Falls Story, Washington State Parks:
"The Washington State Parks and Recreation Commission constructed the Interpretive Center at Dry Falls which houses exhibits and tells the story of the creation of this geological phenomenon. The building overlooks the giant precipice and affords a magnificent view through picture windows. The Grand Coulee, of which Dry Falls is a central feature, has been designated a Registered Natural Landmark by the U.S. Department of the Interior. A bronze plaque to this effect is located in the small vista house adjacent to the parking area."
When water flows over a falls it erodes the area below, called plunge pools. Through a process called abrasion and plucking, water currents can erode the base of the falls and cause the front edge of the falls to collapse into the plunge pool. (See diagram at right > > > ). In this way a river flowing over a falls can "move" the edge of the falls upstream and deposit broken rock downstream. At Dry Falls this action moved the falls some 20 miles north to this location. Various lakes fill in the low areas of the abandoned plunge pools.
Image Copyright © EWU Press
Click on image for a detail view.
USGS Aerial view of Dry Falls. Black areas are water, dark gray areas are shadows.
Compare the width of Highway 17 and the white dot of the Dry Falls Overlook to the length of the falls.
Niagra Falls also has a center island, separating the Canadian and American sides.
[204.8 MM 93 17 S]
Turn right onto Sun Lakes State Park road. This view from the park road clearly shows the uplift in the basalt cliff from pressure from below.
[205.3 MM 93 17 S]
A down lake view of carved islands and scoured cliffs in Sun Lakes State Park. Turning left back onto Highway 17 we continue south.
Here are some basic terms used in the tour. Find more geology terms in the Glossary.
- Volcanic rock caused by partial melting of the Earth's crust.
- A waterfall with a single, sheer drop. Usually with a large volume of water flowing over the falls.
- Plunge Pool
- When water flows over a falls it erodes the area below leaving a hollow spot. The material that was eroded is deposited downstream.
Kids' Cosmos… Expanding Minds Beyond the Limits of the Universe
P.O. Box 14077, Spokane, WA 99206-4077
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