Sugar's Geology Lesson #2 - Smyrna Bench
In Washington, United States
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Sugar and I have been out driving around and learning about the Columbia River Basin geology again (see GC932E - Sugar's Geology Lesson) and so here is #2 of the series. This is an easy cache in an area that contains some beautiful rock formations.
As you drive west down Crab Creek Road from (near) Othello to Beverly you are in the Crab Creek Coulee. About 10 miles west of Othello the slope of the Saddle Mountains (to the south) appear to have dropped to a mere 600 feet high, however this is just an illusion. The rim that you see is not the crest of the Saddle Mountains, but the lip of Smyrna Bench, a ½ mile-wide bluff that hides rugged basalt cliffs above. This cash is hidden just below the Smyrna Bench at 707 feet above mean sea level.
Whatever route you take to the cache, you owe it to yourself to continue west from the cache all the way to the Columbia River.
The cliffs of Saddle Mountain’s north face show layers from all three of the major groups of lava (the Grande Rhonde, Wanapum, and Saddle Mountain Basalt) that inundated this portion of the Columbia Basin between 15.5 million to 10.5 million years ago. Some of the basalt strata are separated by thin layers of conglomerates, siltstones, and sandstones deposited by rivers and streams during lengthy periods between the major eruptions of Columbia River Basalt.
Six miles west of Smyrna, Crab Creek Coulee is nearly a mile wide and 300 feet deep. At this point the currents of the glacial Lake Missoula floods had carved completely through the Elephant Mountain Member of the Saddle Mountains Basalt, but were dissipated enough that they left low islands of underlying Priest Rapids basalt scattered along the floor of the Crab Creek drainage. These whittled outcrops can be seen in the coulee to the north.
Adopted by YeOleImposter on 10/26/2007
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- Looking NortheastLooking northeast across the coulee from near the cache the coulee is only about ¼ miles wide and 150 feet deep. A few miles west of here the coulee joins with another coulee at Red Rock Canyon which ends at a waterfall.
- Looking southLooking south from the cache site you see the lip of the Smyrna Bench which blocks your view of the Saddle Mountains. Behind this picture is Whahatis Peak which is 2692 feet tall.
Last Updated: on 2/18/2013 9:28:07 PM (UTC-08:00) Pacific Time (US & Canada) (5:28 AM GMT)
Coordinates are in the WGS84 datum