aleinge unikah micheline

0 views

Skip to first unread message

Kayleen Dauteuil

unread,

Aug 3, 2024, 9:14:31 PM8/3/24

to stelitroeper

How a Big Black Boring Rock Shaped the Northwest

If you live in the Pacific Northwest, chances are you have seen or heard of the Columbia River Basalt, a massive layer of dark volcanic rock that covers much of the region. But do you know how this big black boring rock came to be, and how it influenced the landscape, history, and culture of the Northwest?

In this article, we will explore the fascinating story of the Columbia River Basalt, based on the book Big Black Boring Rock: Essays on Northwest Geology by Stephen P. Reidel, a geologist and expert on this topic. We will learn about the origin, evolution, and impact of this remarkable geological feature that spans 100,000 square miles and reaches up to 6,000 feet thick in some places.

The Origin of the Columbia River Basalt

The Columbia River Basalt is the result of one of the largest and most violent volcanic events in Earth's history. About 17 million years ago, a series of fissures opened up in eastern Oregon and Washington, spewing out huge amounts of molten lava that flowed across the land like rivers. These lava flows lasted for millions of years, covering most of eastern Washington and Oregon, as well as parts of Idaho, Montana, Nevada, and California.

The lava flows were so massive that they filled up ancient valleys and basins, creating a flat and uniform surface that we call the Columbia Plateau. The lava also reached the Pacific Ocean, where it cooled and solidified into basalt, a hard and dense rock that forms hexagonal columns when it fractures. The basalt cliffs along the Columbia River Gorge are examples of this phenomenon.

The Evolution of the Columbia River Basalt

The Columbia River Basalt did not stay flat and boring for long. Over time, various forces shaped and sculpted it into a diverse and dynamic landscape. Some of these forces include:

Erosion: Wind, water, ice, and gravity eroded away parts of the basalt layer, creating canyons, valleys, hills, and ridges. The most spectacular example of erosion is the Channeled Scablands, a network of dry channels and coulees carved by catastrophic floods during the Ice Age.

Faulting: The movement of tectonic plates caused cracks and breaks in the basalt layer, creating faults and folds. Some of these faults are still active today, causing earthquakes in the region. One of the most prominent faults is the Yakima Fold Belt, a series of ridges and valleys that run parallel to the Cascade Range.

Volcanism: The volcanic activity that created the basalt layer did not stop completely. Some of the fissures remained open or reopened later, producing new lava flows or cinder cones. Some of these volcanoes are still active today, such as Mount St. Helens, Mount Rainier, and Mount Hood.

Glaciation: During the Ice Age, large sheets of ice covered parts of the Northwest, scraping and smoothing the basalt surface. The ice also dammed some rivers, creating huge lakes that overflowed periodically, causing massive floods that reshaped the landscape.

The Impact of the Columbia River Basalt

The Columbia River Basalt has had a profound impact on the Northwest in many ways. Some of these impacts include:

Culture: The basalt layer has influenced the culture and history of the people who live in or near it. For example, Native Americans used basalt rocks to make tools, weapons, art, and monuments. They also used basalt cliffs as landmarks and sacred sites. Later settlers used basalt rocks to build roads, bridges, dams, and buildings.

Economy: The basalt layer has provided many economic opportunities and challenges for the region. For example, basalt rocks are mined for construction materials or crushed for gravel. Basalt cliffs also create hydroelectric power by damming rivers or providing waterfalls. However, basalt rocks also pose hazards such as landslides or earthquakes.