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The cache coordinates will bring you to a family friendly area. Please take care to stay on paths provided, as sensitive dryland plants are present, as well as the possibility of encountering rattlesnakes.
The purpose of this earth cache is to bring people to an area of the Columbia River Gorge where some unique geologic processes have shaped the area in a unique way. The coordinates given will bring you to the start of several walking trails through the area and to the nearby Columbia Gorge Discovery Center located just outside of The Dalles, Oregon.
The Columbia River Gorge is home to many violent geologic processes which have occurred in the span of 100's of thousands of years. Today's landscape is witness to the processes. The Columbia River itself is a powerful waterway which provides resources and recreation alike. The Columbia and Hood rivers have become capitals of windsurfing, and this activity brings windsurfers from across the globe. What some of these surfers may not realize, however, is that their wind and waves today pale in comparison to the mile high surfs that occurred here many years ago!
Fiery floods of Basalt laid the groundwork in the mid-Miocene period for what was to come much later in the Columbia River gorge. Then, between 12 and 6 million years ago, a series of basalt flows came through the Gorge. The largest of these flows (as a group called the Saddle Mountain Basalt flows) was known as the Pomona flow. It covered approximately 7,500 square miles, from North-Central Idaho, following the Snake River and into Pasco, WA where it travelled down the Columbia River all the way to Portland and into the sea.
But burning hot lava was not the only thing that formed the incredible landscape of the Columbia Gorge. In the Pleistocene period, the Columbia River Gorge has been repeatedly affected by flooding which has shaped the geology of the area.
What windsurfers and surfers might have seen on the day when Glacial Lake Missoula (a lake that took up more than 3,000 sq. miles in Montana in a much as 900 feet of water) broke through the ice dam in an Idaho canyon. Lake Missoula drained out of the bottle-neck canyon, travelling at breakneck speed of 17 million gallons per second (per USGS sources). As it went, it scoured clay-rich soils from Idaho, picked up dirt and rocks in Montana and continued on its path of destruction. Just past Wallulah Gap, WA, it caused a backup of the Snake River, then proceeded to surge through the Columbia River Gorge. Despite the distance that it had travelled, and that it had lost a great deal a speed, it is still amazing how the Missoula flood water, travelling now at a mere 10 million cubic yards per second, eroded the southern half of the Columbia Canyon. Sediments from this flood, and smaller inundations, coated the valley floor with 15 feet (more or less) of mucky sediment. In the Willamette Valley today, farmers grow crops from grapes to apples, cherries and pears on what was once rich Montana soil. As the area drained, and the flood waters flowed to the sea, it carried ice-trapped rocks dropping native Montana and Idaho granite erratics - foreigners in a sea of basalts.
Though "the Missoula flood" is the one that is best known - geological scientists have estimated that somewhere between 40 and 89 different floods occurred that shaped the Columbia River Gorge. More than 25 alone were from the same Missoula glacial lake, and exceeded 1,000,000 cubic yards/second as they scoured the Columbia River Gorge.
This earth cache is located at this location as it offers a view of the Columbia River Gorge and excellent examples of the flood's effects on the landscape.
To claim this earth cache, you must email the owner with answers to the following questions and post a picture of yourself/group (with your GPS) showing some of the landscape present. Please do not include any possible spoilers in your pictures.
1) What famous area falls are depicted on the plaque near the coordinates given?
2) According to another nearby plaque, how many flowering indigenous plants are located on these grounds?
3.) What evidence of this ancient flood do you see in the surrounding landscape?
For those interested in learning more about this incredible area, please feel welcome to check out the Columbia Gorge Discovery Center, located nearby. Admission to the Discovery Centre is not a prerequisite to obtaining this earthcache, and no cost is necessary. We hope you enjoy your time in this beautiful area.
Information for this earth cache has been researched from the following sources:
"In Search of Ancient Oregon", by Ellen Morris Bishop.
"Roadside Geology of Oregon", by David D. Alt and Donald W. Hyndman
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