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Models of basaltic volcanism of the eastern Snake River Plain (ESRP), Idaho, provide estimates of crustal basalt magma-driving pressures, magma-supply rates, dike geometry, mass-eruption rates, and durations of eruptions. Magma-driving pressures are 0.1 to 0.2 kb and about 1.2 kb for basalt magma rising from magma reservoirs at 40 and 60 km, respectively. Magma-driving pressures are 0.2 to 0.3 kb and 1.2 kb for basalt and trachyandesite magmas of the Craters of the Moon lava field that rise from a reservoir at 40 km. The lack of vents in several tracts of the ESRP is believed to be related to thick fill of low-density rocks in buried calderas that creates a density barrier that impedes or prevents eruption of basalt magma.

Magma injection by dikes is influenced by regional tectonic extensional stress orientations; eruptive fissures and volcanic rift zones of the ESRP typically are oriented northwest-southeast, perpendicular to minimum regional stresses. Calculated model mass-eruption rates are 9 × 103 kg/sec m for typical ESRP basalt eruptions. Calculated durations of eruptions on the ESRP range from about 25 to 30 hours for the 0.005 km3 Kings Bowl lava field to about 2 months for the 6 km3 Wapi lava field.

An inferred magma-plumbing system includes a magma source region in the mantle at depths of 60 km, a magma reservoir at or near the Moho, magma-filled cracks that transfer magma upward from the reservoir, an upper-level reservoir beneath the Craters of the Moon lava field, and dikes that lead from the reservoir to surface vents.

The relatively unfractionated character of ESRP basalts, long repose intervals between eruptions on most volcanic rift zones, and relatively small volumes of lava fields suggest episodic local melting, little or no accumulation of magma in reservoirs, and rise of magma to the surface fairly directly from the source depth.

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