Wallula Gap
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Wallula Gap
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 Look at the Wallula Gap from Main Street of Wallula from |
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| location | Walla Walla County / Benton County , Washington , USA | |
| Geographical location | 46 ° 3 ' N , 118 ° 57' W | |
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| Setup date | 1980 | |
The Wallula Gap ([ wəˈluːlʌ_gæp ]; English gap = "gap") is a large breakthrough valley of the Columbia River through anticline basalts of the Columbia Plateau in Washington state , just south of the confluence of the Walla Walla and Columbia Rivers. It has been designated a National Natural Landmark by the National Park Service because it marks a significant place in the United States that reveals the geological past.
geology
Basalt rivers
In southeast Washington, eastern Oregon, and southern Idaho , basalt rivers of extremely liquid basaltic lava emerged from long fractures that spread in all directions over great distances, forming gently sloping lava fields. Along the Snake River in Idaho and the Columbia River in Washington and Oregon, these basalt rivers were brought to the surface by erosion . They occasionally show prominent basalt columns . The thickness of the deposits is up to two kilometers.
The basalt rivers visible at the Wallula Gap were deposited in the Miocene about 17 million years ago. They are part of the massive columnar basalt rivers of the Columbia River Basalt Group . During the basalt eruptions , folding processes began in the southern and western Columbia Plateau , which includes the current location of the Wallula Gap. The twists (or shears ) of prehistoric lava flows are clearly visible in the folded basalt layers of the steep slopes at Wallula Gap.
Formation of the Wallula Gap
Even at the beginning of the folds, the ridge at Wallula Gap must have been the lowest in the entire range of hills. The prehistoric Salmon-Clearwater River began to flow over this low point in the mountain range, digging a canal in the process. The folds continued, as did the erosion, and so the breakthrough valley could arise. Until about 10 million years ago, only the Salmon-Clearwater River flowed through the Wallula Gap. As the floodplains in the Columbia Basin sloped further, it was forced to flow east and merge with the Salmon-Clearwater River about 6 million years ago. About 2.5 million years ago the uplift of the Blue Mountains forced the Snake River to move north; he was taken up by the Salmon-Clearwater River near today's Idaho-Oregon border.
Missoula floods
The Wallula Gap was founded around the 14th millennium BC. Chr. By the historical curves of Salmon River , Snake River and Columbia River in combination with the melt waters, which during the Missoula floods across the Channeled Scablands , expanded flows. The Wallula Gap restricted discharge to less than 1/5 of the approximately 800 km³ of water per day that was dammed and could flow into Lake Condon . As a result, the floods filled the Pasco Basin and formed Lake Lewis for a brief period . The massive amounts of water that passed the Wallula Gap contributed substantially to its erosion, which is evident from the shear walls and points such as the Twin Sisters .
During the Missoula Floods, water was retained in the Pasco Basin due to the narrow opening through the Wallula Gap. The floods were so huge that they could not flow quickly enough through the Wallula Gap, even though it is up to two kilometers wide. The water was dammed up to a maximum of 380 meters. The hydraulic potential that was required to cross the Wallula Gap in combination with the altitude below the bottleneck resulted in a tidal wave 250 meters high. The peak runoff has been estimated to be up to 10 million cubic meters per second.
history
Lewis and Clark
The Lewis and Clark Expedition (also known as the Corps of Discovery ) reached Wallula Gap on October 18, 1805, when it set out downstream from camp at the confluence of the Columbia and Snake Rivers. The expedition camped near Spring Gulch Creek for the night and continued through Wallula Gap the next day.
Oregon Trail
In the 1840s, many pioneers turned west on the so-called Oregon Trail and found the Wallula Gap suitable as a stopping point to swap their wagons with boats and continue the route across the Columbia River.
Legend
Twin Sisters Basalt
The Twin Sisters are basalt columns that inspired the mythology of the local residents at Wallula Gap and the Columbia River above Port Kelley, Washington. According to the Cayuse Indians who lived on the Columbia Plateau, the following legend tells of the origin of the rocks:
"Coyote, the Trickster spirit hero of many native stories, fell in love with three sisters who were building a salmon trap on the river near here. Each night Coyote would destroy their trap, and each day the girls would rebuild it. One morning Coyote saw the girls crying and found out that they were starving because they had not been able to catch any fish in their trap. Coyote promised them a working fish trap if they would become his wives. They agreed, and Coyote kept his promise; however, over the years he became jealous of them. He changed two of the wives into these basalt pillars and turned the third into a cave downstream. He became a rock nearby so he could watch over them forever. "
“Coyote, the deceitful ghost hero of many indigenous stories, fell in love with three sisters who built a salmon trap on the river nearby. Every night Coyote broke the trap, and every morning the sisters rebuilt it. One morning Coyote found the sisters crying and learned that they were on the verge of starvation because they had not caught a fish in the trap. Coyote promised them a working trap if they married him. They agreed, and Coyote kept his promise; however, over the years he became jealous of her. He turned two of them into these basalt columns and the third into a cave downstream. He himself became a nearby rock to be able to observe them constantly. "
This location is a popular destination for avid hikers who want to see the geology of Wallula Gap and the effects of the prehistoric Missoula Floods.
Individual evidence
- ^ National Registry of Natural Landmarks . US National Park Service. June 2009.
- ^ USGS Volcano Hazards Program . USGS . Accessed January 30, 2019.
- ^ A b Channeled Scabland of Eastern Washington: The Geologic Story of the Spokane Flood . US Government Printing Office, 1982.
- ^ A b Robert J. Carson, Kevin R. Pogue: Flood Basalts and Glacier Floods: Roadside Geology of Parts of Walla Walla, Franklin, and Columbia Counties, Washington . Washington State Department of Natural Resources (Washington Division of Geology and Earth Resources Information Circular 90), 1996.
- ^ Sand Station Recreation Area (Lake Wallula) . US Army Corps of Engineers. Accessed January 30, 2019.
- ^ Gary E. Moulton: The Journals of the Lewis & Clark Expedition: March 23 – June 9, 1806 . University of Nebraska Press, Lincoln, Nebraska 1991, ISBN 0-8032-2898-8 .
- ^ Governor Clarence D. Martin et. al: Told by Pioneers . WPA Sponsored Federal Project No. 5841, 1937.
- ↑ Cayuse Indians . National Geographic. Archived from the original on March 1, 2018. Retrieved January 30, 2019.
- ↑ Twin Sisters, Washington . Columbia River Images. Accessed January 30, 2019.
- ^ Lewis and Clark Trail Heritage Foundation (eds.): Newsletter . Washington State Chapter, April 2000.
- ^ Judy Bentley: Hiking Washington's History . University of Washington, Seattle 2011.
