The launch of a new GVP website is scheduled for Monday, May 20, 2013.
|Subregion Name:||Idaho (USA)|
|Volcano Type:||Shield volcano|
|Last Known Eruption:||3250 BC ± 150 years|
|Summit Elevation:||1631 m||5,351 feet|
|Hell's Half Acre lava field, the easternmost of the young basaltic lava fields of the Snake River Plain, covers an area of about 400 sq km SW of Idaho Falls and is the 2nd largest of the Snake River Plain. Basaltic lavas forming the broad, low shield volcano are dominantly pahoehoe flows that were erupted from a 3-km-long, NW-SE trending vent system at the NW part of the field during a brief eruptive episode about 5200 years ago. The summit vent area contains an irregular, elongate 0.8 x 0.3 km wide central depression that was the site of a former lava lake that fed late-stage flows. About 10 circular pit craters truncate the surface of the lava lake, and two prominent lava tube systems are located near the summit vent complex. Two major lava flow lobes, each about 5 km wide and 10 km long, extend to the south and SW along the flood plain of the Snake River and surround Morgans Pasture, a large kipuka. Interstate 15 highway crosses the SE margin of the lava field SW of the city of Idaho Falls.|