Hell's Half Acre Lava Field
| Hell's Half Acre Lava Field | |
|---|---|
View of Hell's Half Acre Lava Field
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| Highest point | |
| Elevation | 1,631 metres (5,351 ft) |
| Coordinates | 43°30′N 112°27′W / 43.50°N 112.45°W |
| Geography | |
| Location | Bonneville and Bingham counties, Idaho, U.S. |
| Geology | |
| Mountain type | Shield volcano, lava plain |
| Last eruption | 3250 BCE ± 150 years |
| Designated | 1976 |
Hell's Half Acre Lava Field is a basaltic lava plain located on the Snake River Plain of Idaho in the United States. It is the easternmost of the basaltic lava fields on the Snake River Plain, located about 25 miles (40 km) west of Idaho Falls, Idaho and 30 miles (48 km) north of Pocatello, Idaho. In 1976, the National Park Service designated the northwestern portion of the site a National Natural Landmark. In 1986, the Bureau of Land Management recommended that 68,760 acres (27,830 ha) of the site, located just southeast of the National Natural Landmark, to be a wilderness study area.
The Hell's Half Acre lava plain is located in Bingham and Bonneville counties in the state of Idaho. The site is about 150 square miles (390 km2) in size. The area where a former lava lake existed is marked by a 875-yard (800 m) long by 328-yard (300 m) wide depression near the summit of the lava field. Ten circular pits and two large lava tubes are also located near the summit. Two major lava flows, each about 6.2 miles (10.0 km) long by 3.1 miles (5.0 km) wide, extend from the main lava field to the south and southwest. These two lava flows surround "Morgans Pasture," a kipuka (or older geologic feature which was not covered by lava). More recently, scientists studying aerial photographs of the site discovered a 328-yard (300 m) long eruptive fissure partly buried under lava flows just 437 yards (400 m) from the northwest boundary of the lava field. This and other features of the site indicate that the fissure vent itself may be 11.8 miles (19.0 km) long.
The site is fairly accessible. Interstate 15 just crosses the southeast corner of the lava field. Two trails have been marked by U.S. Bureau of Land Management personnel. The shorter, 0.5-mile-long (0.80 km) trail is marked by blue flags, and takes about 30 minutes to walk. The longer, 4.5-mile-long (7.2 km) trail is marked by red flags, and takes a full day to walk. The latter trail leads to the central vent. A short trail (about 0.75 miles (1.21 km) in length) with educational signage along the way may be accessed from the north parking lot near the Hell's Half Acre rest area on I-15. A second trail (about 1 mile (1.6 km) in length) with educational signage may be accessed from the south parking lot. This longer trail has a gazebo and scenic overlook at about the midpoint. There is also a 0.25-mile-long (0.40 km) handicapped-accessible paved loop with educational signage as well. All trails are closed in winter. Over 100,000 people used the trails in 2007.
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