Columbia River Basalt Group

acronym

CRBG

Miocene

During the middle to late Miocene epoch, the Columbia River flood basalts engulfed about 163,700 km2 (63,200 sq mi) of the Pacific Northwest, forming a large igneous province with an estimated volume of 174,300 km3 (41,800 cu mi).

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Editor’s Note: Mr. Thiel has further elaborated on the question of suffrage here. We copy these remarks below as well:

self-guided tour of the geology

A self-guided tour of the geology of the Columbia River Gorge–Portland Airport to Skamania Lodge, Stevenson, Washington (dnr.wa.gov) (PDF) Washington is uniquely positioned for the study of the geologic and structural setting of western North America. To the south in Oregon and Nevada, extensional features predominate as reflected by basin-and-range terrain. To the east, the Rocky Mountains influence the geology of Idaho. To the north, western British Columbia is characterized by a massive coastal crystalline belt and remnants of the geologic continent Wrangellia. All of these major crustal features of the adjacent regions terminate in or near Washington…

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Columbia River Basalt Group Stretches from Oregon to Idaho (usgs.gov) The thick, layered lava flows of the CRBG erupted as flood basalts, which originate as some of the most highly effusive eruptions in the world. The CRBG sequence a classic example of flood basalt activity that erupted more than 350 lava flows from about 16.7 Ma to 5.5 Ma. The eruptions originated from a series of generally north-northwest-trending linear fissures, ranging from tens to hundreds of kilometers in length, located along the Washington/Oregon/Idaho border. The magma that fed these massive eruptions may have come from a plume-like upwelling from the mantle called a hot spot. Since the time of the CRBG eruptions, the North American plate has moved in a west-southwestwardly motion, and that hot spot is now believed to reside beneath Yellowstone volcano in northwest Wyoming.
Field-trip guide to the vents, dikes, stratigraphy, and structure of the Columbia River Basalt Group, eastern Oregon and southeastern Washington (usgs.gov) This field-trip guide explores the main source region of the CRBG and is written for trip participants attending the 2017 International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Scientific Assembly in Portland, Oregon, USA. The first part of the guide provides an overview of the geologic features common in the CRFBP and the stratigraphic terminology used in the CRBG. The accompanying road log examines the stratigraphic evolution, eruption history, and structure of the province through a field examination of the lavas, dikes, and pyroclastic rocks of the CRBG

Wikipedia

Columbia River Basalt Group (Wikipedia) The Columbia River Basalt Group is the youngest, smallest and one of the best-preserved continental flood basalt province on Earth, covering over 210,000 km2 (81,000 sq mi) mainly eastern Oregon and Washington, western Idaho, and part of northern Nevada. The basalt group includes the Steens and Picture Gorge basalt formations.