A comparative account of the flood basalt volcanism of the Columbia Plateau and Eastern Iceland

Abstract

An introduction to the flood basalt volcanism of the Columbia Plateau and Eastern Iceland is followed by more detailed comparative notes. These stress that the volcanism in the two areas was of the same general type. In both regions sub-aerial fissure eruptions gave rise to very extensive basalt flows, particularly on the Columbia Plateau, where some individual lavas cover more than 10,000 km2. The feeding fissures were localized in swarms, and this led in each case to the development of thick, low, shield-like accumulations of flows over the source areas. Progressive (isostatic?) subsidence of the central parts of the basalt pile accentuated the natural tendency for the succession to be thickest in the neighborhood of the feeding fissure swarms. Related differentiates were erupted from the central parts of the fissure vent areas, while olivine-rich basalt flows were apparently often erupted from the edges of the main swarm.