ESSAY: On the geology of Columbia River Gorge

DB-10

Students if you go to course documents you will view our own experiences/images on/about the Gorge when we were there in late April; please visit Course Documents to see our account which should bring additional meaning to your discussions.

During what geological era or period(s) was the Columbia River Gorge formed? Thus how old is gorge.
What unique geological/tectonic processes (based on what you have learned in this course or your internet search) led to the formation of the Gorge.
What are the principal rocks, geological, hydrological features of the Gorge?
Discuss the drainage area that leads to the water that enters the Columbia River
When and why was Bonneville Dam (within the gorge) and what environmental issues are currently being discussed or argued on the value of this dam project?

ANSWER

On the Geology of Columbia River Gorge

The Columbian River Gorge refers to a canyon that is part of the Columbian River in the United States. The Gorge is about 4000 feet deep; and it forms the boundary between Oregon and Washington to the north. The Columbian River Gorge was formed during the Miocene geological era, which is about 12 million years ago (Mangan et al., 1986). This was a time when several Cascade Ranges were forming, and they led to the development of the River’s delta from the existing or current location.

During the formation of the Gorge, there was the lifting of granite from the core of the earth. This formation took place within the area, and it led to flooding with lava, which was caused by frequent volcanic eruptions. The lava was made up of mud, and ash which cooled down to form the base of the Gorge (Palmer, 1977). The base underwent a faster cooling as compared to what was experienced at the top. The drainage area that leads to the water in the Columbia River is about 670,000 square kilometers (Williams, 1923). The drainage area consists of mountains, river valleys, and deep gorges. The Grand Teton National Park is also part of the natural features that are in the drainage area.

The Bonneville Dam is well known to be among the first mainstream of the Columbia River. The main aim of coming up with the dam was to provide room for the generation of electricity in the year 1933 (Smith, 1992). The major environmental issues that are discussed in line with the dam project is that it has interfered with the migration of the white sturgeon. This means that the spawning seasons of the white sturgeon have changed, and many of them are now reducing in number.

References

Mangan, M. T., Wright, T. L., Swanson, D. A., & Byerly, G. R. (1986). Regional correlation of Grande Ronde Basalt flows, Columbia River Basalt Group, Washington, Oregon, and Idaho. Geological Society of America Bulletin, 97(11), 1300-1318.

Palmer, L. (1977). Large landslides of the Columbia River gorge, Oregon and Washington. Reviews in Engineering Geology, 3, 69-83.

Smith, A. D. (1992). Back-arc convection model for Columbia River basalt genesis. Tectonophysics, 207(3-4), 269-285.

Williams, I. A. (1923). The Columbia River Gorge: Its Geologic History Interpreted from the Columbia River Highway (Vol. 2, No. 3). James, Kerns & Abbot.