HELL'S HALF ACRE
ATOMIC CITY - IDAHO, USA
The Great Rift System is a fissure zone that arcs across the Eastern Idaho Snake River plain, It is split into 4 different rift sets which affect the Plains.
(1) The Great Rift Set
(2) Open crack Rift Set
(3) King's Bowl Rift Set
(4) Wapi Rift Set
Hell's Half Acre is not part of the Great rift zone but a part of a smaller rifting zone called the Lava Ridge-Hell's Half Acre Volcanic Rift Zone, as the Volcano sits just East of the Western Arcing Great Rift Zone.
The Hell's Half Acre Shield Volcano has no chance of erupting again as it is a Monogenetic volcano. Volcanoes that are classified as Monogenetic are usually short-lived, they are fed by small volume magma chambers which in turn produce small volume volcanoes.
These volcanoes are usually in close proximity to larger Polygenetic volcanoes which erupt more than once in their lifetime. A good example of a close Polygenetic volcanic system is Craters Of The Moon.
View from the dirt road off W Arco Hwy of Hell's Half Acre
Hell's Half Acre is a Shield Volcano that formed from mostly Pahoehoe Lava Flows. The Lava Flows in Hell's Half Acre are one of the youngest in the Snake River Plain, the volcano erupted around 5,200 years ago in a brief eruptive episode. Craters of the Moon is considered older as its first eruption was around 15,000 years ago although its youngest was only 2,000 years ago.
The vent area around the summit once contained a Lava Lake which fed late-stage lava flows, and 2 major lava-tube systems which are located close to the summit of the Shield Volcano.
The Basaltic Lava Flows cover a 400 km2 area, which puts the flows as the second-largest lava flows in the Snake River Plain of Idaho, only rivaled by the Craters Of The Moon lava flows. The Pahoehoe Lava Flows erupted from a 3-km-long Northeast Southeast trending vent system located at the Northwest end of the Lava Field.
By Boris Chako Tchamabé, Gabor Kereszturi, Karoly Németh and Gerardo Carrasco‐Núñez
Submitted: November 23rd 2015 Reviewed: April 6th 2016 Published: September 21st 2016
Martin Prinz; Idaho Rift System, Snake River Plain, Idaho. GSA Bulletin