Bridge of the Gods EarthCache
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The Bridge of the Gods, the Cascade Mountains and the Columbia River
The Columbia River Plateau was created by a series of basalt flows. The flows covered 164,000 square kilometers –including parts of Oregon, Washington and Idaho.
Table Mountain is on the Washington side of the Columbia River, west of the Bridge of the Gods. Table Mountain consists of Columbia Basalt on top of a softer clay-filled formation. It has been describes as "a deck of cards that is pointing and sliding toward the river," by Alex Bourdeau, an archaeologist with the U.S. Fish and Wildlife Service (Hill). Several hundred years ago Table Mountain and Greenleaf Peak on the Washington side of the Columbia, split in two; the southern halves of them slid down the mountain and into the Columbia, forming a natural dam approximately 200 feet high and 3.5 miles long, three times the height of Bonneville Dam. Some rocks were as big as 800 feet long and 200 feet thick. Water filled up to 80 feet deep forming a lake which drowned a forest of trees for 35-100 miles along the. The landslide, (known as the Bonneville Landslide) and resulting dam diverted the channel of the Columbia a mile to the south. This dam became known as The Bridge of the Gods.
The exact date of the Bonneville Landslide is an unresolved issue among people studying it. Early work based on dendrochronology and radiocarbon dating suggested the landslide occurred between 1060 and 1180. More recent work using radiocarbon dating and lichenometry has suggested dates between 1500 and 1760. Geologists have determined that debris from four distinct landslides in the same area overlap, forming what is called the Cascades landslide complex. The Bonneville landslide is the most recent of the documented Cascade Landslide Complex.
Although no one knows how long it took, the Columbia River eventually broke through the dam. The water rushed downstream in a torrent, scouring the landscape and washed away most of the debris, forming the Cascade Rapids, as they were described by Lewis and Clark as “cascading”. These rapids incidentally are also how the Cascade Mountains got their name. The cascades were also a barrier to navigation until the late 1890's, when the Cascade Locks were built.
The Gorge is still changing. In the winter of 1996, landslides similar to the Bridge of the Gods landslide destroyed homes in Warrendale. At milepost 35 on I-84 you can see this damage.
The bridge we see now was constructed in 1926, and is the third oldest bridge on the Columbia River. It plays a major role in the Pacific Crest Trail by linking Oregon and Washington states.
Native American legend
Native American lore contains numerous legends to explain the eruptions of Mount St. Helens and other volcanoes in the Cascade volcanic arc. The most famous of these is the Bridge of the Gods legend told by the Klickitats. In their tale, the chief of all the gods, Tyhee Saghalie and his two sons, Pahto (also called Klickitat) and Wy'east, traveled down the Columbia River from the Far North in search for a suitable area to settle.
They came upon an area that is now called The Dalles and thought they had never seen a land so beautiful. The sons quarreled over the land and to solve the dispute their father shot two arrows from his mighty bow; one to the north and the other to the south. Pahto followed the arrow to the north and settled there while Wy'east did the same for the arrow to the south. Saghalie then built Tanmahawis, the Bridge of the Gods, so his family could meet periodically.
When the two sons of the Saghalie fell in love with a beautiful maiden named Loowit, she could not choose between them. The two young chiefs fought over her, burying villages and forests in the process. The area was devastated and the earth shook so violently that the huge bridge fell into the river, creating the Cascades Rapids of the Columbia River Gorge.
For punishment, Saghalie struck down each of the lovers and transformed them into great mountains where they fell. Wy'east, with his head lifted in pride, became the volcano known today as Mount Hood and Pahto, with his head bent toward his fallen love, was turned into Mount Adams. The fair Loowit became Mount St. Helens, known to the Klickitats as Louwala-Clough which means "Smoking or Fire Mountain" in their language.
To log this earthcache email the cache owner:
1. What was probably the cause of the massive landslides?
2. What mountains were affected?
3. Why type rock is located in the area?
4. Approximately what is the distance across the river at this point? Is that less or more than most of the river?
5. What is illustrated on the bottom of the middle information board at the coordinates?
6. Take a photo of your party and gps at the posted coordinates.
References
1. Reynolds, Nathaniel D. (December 2001). "Dating the Bonneville Landslide with Lichenometry". Washington Geology 29 (3/4): 11–16. (visit link) Retrieved 2009-09-07.
2. Hill, Richard L. (September 9, 1999). "Radiocarbon dates indicate the Bonneville Landslide may be far younger than thought". The Oregonian. (visit link)
3. O'Connor, Jim E. (September 2004). "The Evolving Landscape of the Columbia River Gorge: Lewis and Clark and Cataclysms on the Columbia". Oregon Historical Quarterly 105 (3). (visit link) Retrieved 2009-09-07.
4. Hill, Richard L. (May 15, 2002). "Science - Landslide Sleuths". The Oregonian. (visit link)
5. Archie Satterfield, Country Roads of Washington (Backinprint.com: 2003) ISBN 0-595-26863-3, page 82
6. The Bridge of the Gods, theoutlaws.com (accessed 26 November 2006)
7. Great Cascadia Earthquake Penrose Conference – The Oregonian Article Science – Landslide Sleuths (May 15, 2002). (visit link)
8. Landslide blocks the Columbia River in about 1450. (visit link)
9. Bridge of the Gods (land bridge) (visit link)
10. USE OF DENDROCHRONOLOGY TO DATE AND BETTER UNDERSTAND THE BONNEVILLE LANDSLIDE, COLUMBIA RIVER GORGE, WASHINGTON (visit link)
11. Myths and Legends: Oregon's Bridge of the Gods: Pacific Northwest Native Lore Inspired by Mt Hood, Mt St Helens (visit link)
12. U.S. Army Corps of Engineers, Portland District, and the U.S. Department of the Interior, U.S. Geological Survey, The Geologic History of the Columbia River Gorge: Information Brochure (visit link)
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