Sheer Drops, Sculpted Islands and Cliff Caves
[209.5 MM 89]
In the road cut we see these lakebeds beneath the basalt. This indicates that at some time before the numerous basalt flows these white sediments were deposited by a body of water. Near these lakebeds pillow basalt is exposed as seen at right. Click on image for a detail view.
Not too far from here hikers found the fossil of an extinct rhinoceros, called Diceratherium, in 1935. It's dead body was apparently lying in water when it was covered by an advancing basalt flow. The water protected it from the intense heat and left the fossil in a cavity containing several teeth and pieces of fossilized bone. Some of these fossils can be seen at the Dry Falls Museum.
[214.8 MM 86]
We have turned left to look at the Lake Lenore Caves. These caves were formed when floodwaters plucked basalt columns out of the cliffs. There is evidence that Native Americans used these caves for shelters and storage areas while hunting and gathering food in the coulee.
|"These alcoves in the basalt flows were created by a plucking process in the wake of the passing floodwaters through the Lower Grand Coulee. Underwater "tornadoes" or kolks created low pressure zones that lifted the basalt into the current, no doubt assisted by the fractured, columnar jointed aspect of the rock." [Buchanan]|
|"The turn-off takes you to a parking area and interpretive sign. A paved path with steps leads you up the cliff to several caves. The view across the coulee and Lake Lenore is spectacular from this elevation." [Draggoo]|
[217.8 MM 82]
View above the highway on left of caves. Continue south on Highway 17 to Soap Lake.
A note about prehistoric people and the Lake Lenore Caves from The Dry Falls Story, Washington State Parks:
"Caves formed by the plucking of basalt from the walls of the coulees by the rush of melt waters were later used as shelters by prehistoric man. A band on the move carried only the bare essentials in the way of material culture, and a family spending a few days in a cave would know what they brought with them and would be sure to leave with the same. Therefore, the absence of any large or valuable artifacts such as pestles in the caves today suggests they were used by a temporary and migratory population. The type of artifact most likely to be lost was the small scraper used in the preparation of skins. This tool is the artifact most commonly found in the caves.
The population of this area was undoubtedly small, but because the people were hunters and gatherers of plant food, they must have been almost constantly on the move in search of food. A trail leading to some of these caves has been developed near the north end of Lake Lenore."
Lakes and Lakebeds
Lakes are formed in depressions in the Earth's surface. Where streams or rivers flow into a lake the water tends to rise in the depression until it overflows into an outlet stream. Lakes with no outlet become salty and alkaline such as Soap Lake, Washington and the Great Salt Lake, Utah. We swim, boat, fish and other activities in lakes without much thought about how they form or disappear.
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.
- Long winding channel cut through lava formations. A term primarily used in the northwestern United States.
- A whirlpool or tornado effect that forms in deep, fast moving water. Kolks can pick up solid blocks of basalt in flood areas.
- Pale yellow, glassy material that forms when hot steam and other gases contact water during a lava flow. Sand and clay is usually mixed in as well.
- Pillow Basalt
- Basalt formed underwater or as a basalt flow contacts a river or lake.
- Collection of sand, silt, gravel and organic material that sinks to the bottom of a river, lake or ocean. Some or all of these materials may be present.
- Layers of light and dark sediment on the floor of a glacial lake. Each light and dark pair indicates a year since light deposits are from rock dust from melting ice in summer and dark layers are from organic matter.
Kids' Cosmos… Expanding Minds Beyond the Limits of the Universe
P.O. Box 14077, Spokane, WA 99206-4077
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