Columbia River Basalt Group

The Columbia River Basalt Group is a large igneous province in the Pacific Northwest, built from repeated flood-basalt eruptions about 17 to 6 million years ago.

Flood basalt: A flood basalt is a vast accumulation of basaltic lava erupted over a geologically short interval. The group is one of the clearest continental examples of this eruption style.
Yakima Basalt Subgroup: The Yakima Basalt Subgroup is the main subdivision of the Columbia River Basalt Group in Washington and Oregon. Its formations organize most of the group's best-known flows.
Yellowstone hotspot: The Yellowstone hotspot is a long-lived mantle heat source associated with a track of volcanic centers across western North America. Its older track has been proposed to begin with Columbia River Basalt magmatism.
Columbia River Gorge: The Columbia River Gorge is a canyon cut by the Columbia River through the Cascade Range between Oregon and Washington. Its cliffs expose thick sequences of Columbia River Basalt flows.
Roza Member: The Roza Member is a Columbia River Basalt flow unit recognized across parts of Washington and Oregon. Its extensive outcrops illustrate how a single eruption could spread far beyond its vent region.
Grande Ronde Basalt: The Grande Ronde Basalt is the thickest and most extensive formation in the Columbia River Basalt Group. Its many flows account for most of the group's total volume.
Steens Basalt: Steens Basalt is an early Miocene flood-basalt unit in southeastern Oregon, commonly linked to the Columbia River Basalt Group. It represents some of the earliest eruptions in the province's development.
North American plate: The North American Plate is the tectonic plate carrying most of North America and parts of the Atlantic seafloor. Its motion over mantle sources helps frame reconstructions of the province's origin.
Columbia Plateau: The Columbia Plateau is a broad region of the Pacific Northwest underlain largely by Columbia River Basalt flows. The plateau's landforms and soils reflect the province's extensive lava cover.
Frenchman Springs Member: The Frenchman Springs Member is a sequence of flows within the Wanapum Basalt. Its multiple flow units capture the complexity of a major eruptive interval.

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