The Columbia River Basalt Group comprises a tholeiitic flood-basalt province of moderate size, covering an area of about 2x105 square kilometers, with an estimated volume of about 2x105 cubic kilometers. The group is the youngest assemblage of flood basalt known, with an age range from about 17 to 6 million years ago; most eruptions took place between about 17 and 14 million years ago. It is the only flood basalt province of Phanerozoic age in North America. -- Swanson and Wright |