Hell's Half Acre Lava Field
Encyclopedia
Hell's Half Acre lava field is a basalt
ic 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 (40.2 km) west of Idaho Falls, Idaho
and 30 miles (48.3 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 68760 acres (27,826.2 ha) of the site, located just southeast of the National Natural Landmark, to be a wilderness study area
.
and Bonneville
counties in the state of Idaho. The site is about 150 mi2 in size. The area where a former lava lake existed is marked by a 875 yards (800.1 m) long by 328 yards (299.9 m) wide depression near the summit of the lava field. Ten circular pits and two large lava tube
s are also located near the summit. Two major lava flows, each about 6.2 miles (10 km) long by 3.1 miles (5 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 yards (299.9 m) long eruptive fissure partly buried under lava flows just 437 yards (399.6 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 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 (0.80467 km) long trail is marked by blue flags, and takes about 30 minutes to walk. The longer, 4.5 miles (7.2 km) long 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 (1.2 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 miles (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 mid-point. There is also a 0.25 mile (0.402335 km) long handicapped-accessible paved loop with educational signage as well. All trails are closed in winter. Over 100,000 people used the trails in 2007.
The Hell's Half Acre lava plain is home to a variety of plant species. Among them are bitterbrush
, bluebunch wheatgrass, death camas
, evening primrose
, fern
s, geraniums, gray rabbitbrush
, Indian paintbrush
, needle-and-thread grass
, penstemon
, prickly pear cactus
, sagebrush
, Utah juniper
, and wild onion
. Wildlife is also abundant. Species commonly found here include bobcat
s, coyote
s, golden eagle
s, mule deer
, prairie falcon
s, pronghorn antelope
, red fox
es, red-tailed hawk
s, and sage grouse.
. The lava field was created by the Lava Ridge-Hell's Half Acre fissure vent
, and marks the southern edge of this area of volcanic activity. This fissure vent was created when one or more magmatic dikes (sheets or tubes of magma cutting across the existing geologic features) found their way to the surface. At the northwestern edge of the lava field is a shield volcano
, with the fissure vent extending toward the southeast and the Hell's Half Acre site. Pit crater
s and spatter cones follow this active fissure line. Two non-erupting fissures extend northwest from the shield volcano for about 2.7 miles (4.3 km). One scientific team hypothesized that the seven lava fields in the vicinity of Hell's Half Acre may belong to as few as two fissure vents.
Hell's Half Acre was created when basaltic pāhoehoe quickly flowed out of the volcanic rift. At least eight lava lobes have been identified by geologists. As magma
and volcanic gases drained from underneath the lava field, the field subsided—leaving behinds hummocks, or "hills" of lava (a feature which Hell's Half Acre retains today). There is evidence that lava filled and drained the lava lake numerous times, and that lava repeatedly overflowed the lake.
Lava from the fissure vent tended to flow downhill toward the southeast, covering part of the fissure. Lava tubes extend in a generally southeastern direction under the lava field, and surfaced in the far southeastern corner of the site. There is also evidence that later pāhoehoe lava lobes ran underneath or inside existing lobes, and then broke out.
The current name of the lava field was given to it by fur traders in the early 19th century seeking passage through the rough terrain of the Rocky Mountains
. The term "hell's half acre" was a commonly used expression to describe any rough land. One of the first white people to record their visit to Hell's Half Acre was Benjamin Bonneville
, a French
-born United States Army
officer. Bonneville traveled west in 1832, on a leave of absence from the military. His expedition was financed by the wealthy fur trade
r, John Jacob Astor
. Bonneville saw the site in 1833. The celebrated writer Washington Irving
used Bonneville's journals to write a book about the expedition, and based on his descriptions wrote about the area this way:
In the late 19th century and early 20th century, the area was the center of logging activity. Red cedar
grew abundantly in the lava field, as the plant can grow directly on rock. In 1889, the village of Woodville (now a ghost town
) was founded near the Woodville Bend of the Snake River (near the modern town of Shelley, Idaho
). The Woodville settlers harvested large amounts of red cedar for use as lumber and fuel. These practices were significantly cut back in the 1910s and 1920s as coal became more widely available as a fuel, but the harvesting of red cedar from Hell's Half Acre continued until 1942.
A wildfire
burned 500 acres (202.3 ha) of the site in 1999. In the fall of 2005, Michael Curtis Reynolds
was arrested at the Hell's Half Acre rest area after the Federal Bureau of Investigation
lured him there with the promise of money and arms from a supporter. More recently, in 2006 the utility Utah Power
tried to build an electrical substation
near the eastern-most part of Hell's Half Acre lava field.
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic lava plain
Lava plain
A lava plain, also called a lava field or lava bed, is a large expanse of nearly flat-lying lava flows. Such features are generally composed of highly-fluid basalt lava, and can extend for tens or even hundreds of miles across the underlying terrain...
located on the Snake River Plain
Snake River Plain
The Snake River Plain is a geologic feature located primarily within the state of Idaho in the United States of America. It stretches about westward from northwest of the state of Wyoming to the Idaho-Oregon border. The plain is a wide flat bow-shaped depression, and covers about a quarter of Idaho...
of Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. It is the easternmost of the basaltic lava fields on the Snake River Plain, located about 25 miles (40.2 km) west of Idaho Falls, Idaho
Idaho Falls, Idaho
Idaho Falls is a city in and the county seat of Bonneville County, Idaho, United States, and the largest city in Eastern Idaho. As of the 2010 census, the population of Idaho Falls was 56,813, with a metro population of 130,374....
and 30 miles (48.3 km) north of Pocatello, Idaho
Pocatello, Idaho
Pocatello is the county seat and largest city of Bannock County, with a small portion on the Fort Hall Indian Reservation in neighboring Power County, in the southeastern part of the U.S. state of Idaho. It is the principal city of the Pocatello metropolitan area, which encompasses all of Bannock...
. In 1976 the National Park Service
National Park Service
The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...
designated the northwestern portion of the site a National Natural Landmark
National Natural Landmark
The National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...
. In 1986, the Bureau of Land Management recommended that 68760 acres (27,826.2 ha) of the site, located just southeast of the National Natural Landmark, to be a wilderness study area
Wilderness study area
A wilderness study area contains undeveloped United States federal land retaining its primeval character and influence, without permanent improvements or human habitation, and managed to preserve its natural conditions...
.
Description of the site
The Hell's Half Acre lava plain is located in BinghamBingham County, Idaho
Bingham County is a county located in the U.S. state of Idaho. As of the 2000 Census the county had a population of 41,735 . The county seat and largest city is Blackfoot. Bingham County comprises the Blackfoot, ID, Micropolitan Statistical Area.Bingham County was created January 13, 1885, and...
and Bonneville
Bonneville County, Idaho
Bonneville County is a county located in the U.S. state of Idaho. As of the 2010 census, the county had a population of 104,234. Its county seat and largest city is Idaho Falls...
counties in the state of Idaho. The site is about 150 mi2 in size. The area where a former lava lake existed is marked by a 875 yards (800.1 m) long by 328 yards (299.9 m) wide depression near the summit of the lava field. Ten circular pits and two large lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...
s are also located near the summit. Two major lava flows, each about 6.2 miles (10 km) long by 3.1 miles (5 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 yards (299.9 m) long eruptive fissure partly buried under lava flows just 437 yards (399.6 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 km) long.
The site is fairly accessible. Interstate 15
Interstate 15
Interstate 15 is the fourth-longest north–south Interstate Highway in the United States, traveling through the states of California, Nevada, Arizona, Utah, Idaho, and Montana from San Diego to the Canadian border...
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 (0.80467 km) long trail is marked by blue flags, and takes about 30 minutes to walk. The longer, 4.5 miles (7.2 km) long 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 (1.2 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
Rest area
A rest area, travel plaza, rest stop, or service area is a public facility, located next to a large thoroughfare such as a highway, expressway, or freeway at which drivers and passengers can rest, eat, or refuel without exiting on to secondary roads...
on I-15. A second trail (about 1 miles (1.6 km) in length) with educational signage may be accessed from the south parking lot. This longer trail has a gazebo
Gazebo
A gazebo is a pavilion structure, sometimes octagonal, that may be built, in parks, gardens, and spacious public areas. Gazebos are freestanding or attached to a garden wall, roofed, and open on all sides; they provide shade, shelter, ornamental features in a landscape, and a place to rest...
and scenic overlook at about the mid-point. There is also a 0.25 mile (0.402335 km) long handicapped-accessible paved loop with educational signage as well. All trails are closed in winter. Over 100,000 people used the trails in 2007.
The Hell's Half Acre lava plain is home to a variety of plant species. Among them are bitterbrush
Purshia
Purshia is a small genus of 5-8 species of flowering plants in the family Rosaceae, native to western North America, where they grow in dry climates from southeast British Columbia in Canada south throughout the western United States to northern Mexico. The classification of Purshia within the...
, bluebunch wheatgrass, death camas
Death Camas
Zigadenus venenosus, commonly called death camas or meadow deathcamas, is a flowering plant in the genus Zigadenus belonging to the Melanthiaceae. It grows up to 70 cm tall with long, basal, grass-like leaves. The bulbs are oval and look like onions but do not smell like onions...
, evening primrose
Oenothera
Oenothera is a Genus of about 125 species of annual, biennial and perennial herbaceous flowering plants, native to North and South America. It is the type genus of the family Onagraceae, the Evening Primrose Family. Common names include evening-primrose, suncups, and sundrops.The species vary in...
, fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s, geraniums, gray rabbitbrush
Ericameria
Ericameria is a genus of shrubs in the Asteraceae or daisy family known by the common names rabbitbrush, rabbitbush, and goldenbush. These are semi-deciduous shrubs familiarly known as to sagebrush. They are distributed in the arid western United States and northern Mexico. Bright yellow flowers...
, Indian paintbrush
Castilleja
Castilleja, commonly known as Indian paintbrush or Prairie-fire, is a genus of about 200 species of annual and perennial herbaceous plants native to the west of the Americas from Alaska south to the Andes, northern Asia, and one species as far west as the Kola Peninsula in Siberia...
, needle-and-thread grass
Hesperostipa comata
Hesperostipa comata, commonly known as needle-and-thread grass, is a species of grass native to North America, especially the western third. It has a wide distribution spanning from northern Canada to Mexico.-Description:...
, penstemon
Penstemon
Penstemon , Beard-tongue, is a large genus of North American and East Asian plants traditionally placed in the Scrophulariaceae family. Due to new genetic research, it has now been placed in the vastly expanded family Plantaginaceae...
, prickly pear cactus
Opuntia
Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...
, sagebrush
Artemisia tridentata
Artemisia tridentata is a shrub or small tree from the family Asteraceae. Some botanists treat it in the segregate genus Seriphidium, as S. tridentatum W. A. Weber, but this is not widely followed...
, Utah juniper
Juniperus osteosperma
Juniperus osteosperma is a shrub or small tree reaching 3-6 m tall. It is native to the southwestern United States, in Utah, Nevada, Arizona, western New Mexico, western Colorado, Wyoming, southern Montana, southern Idaho and eastern California...
, and wild onion
Allium validum
Allium validum, known by several common names including swamp onion, wild onion, Pacific onion, and Pacific mountain onion, has been previously classified as a member of the lily family, Liliaceae; however, it is now thought to be in the Alliaceae...
. Wildlife is also abundant. Species commonly found here include bobcat
Bobcat
The bobcat is a North American mammal of the cat family Felidae, appearing during the Irvingtonian stage of around 1.8 million years ago . With twelve recognized subspecies, it ranges from southern Canada to northern Mexico, including most of the continental United States...
s, coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...
s, golden eagle
Golden Eagle
The Golden Eagle is one of the best known birds of prey in the Northern Hemisphere. Like all eagles, it belongs to the family Accipitridae. Once widespread across the Holarctic, it has disappeared from many of the more heavily populated areas...
s, mule deer
Mule Deer
The mule deer is a deer indigenous to western North America. The Mule Deer gets its name from its large mule-like ears. There are believed to be several subspecies, including the black-tailed deer...
, prairie falcon
Prairie Falcon
The Prairie Falcon is a medium-sized falcon of western North America.It is about the size of a Peregrine Falcon or a crow, with an average length of 40 cm , wingspan of 1 metre , and weight of 720 g...
s, pronghorn antelope
Pronghorn
The pronghorn is a species of artiodactyl mammal endemic to interior western and central North America. Though not an antelope, it is often known colloquially in North America as the prong buck, pronghorn antelope, or simply antelope, as it closely resembles the true antelopes of the Old World and...
, red fox
Red Fox
The red fox is the largest of the true foxes, as well as being the most geographically spread member of the Carnivora, being distributed across the entire northern hemisphere from the Arctic Circle to North Africa, Central America, and the steppes of Asia...
es, red-tailed hawk
Red-tailed Hawk
The Red-tailed Hawk is a bird of prey, one of three species colloquially known in the United States as the "chickenhawk," though it rarely preys on standard sized chickens. It breeds throughout most of North America, from western Alaska and northern Canada to as far south as Panama and the West...
s, and sage grouse.
History of the site
Geologists estimate that the Hell's Acre Lava Field was created about 3250 BCECommon Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...
. The lava field was created by the Lava Ridge-Hell's Half Acre fissure vent
Fissure vent
A fissure vent, also known as a volcanic fissure or simply fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is usually a few meters wide and may be many kilometers long. Fissure vents can cause large flood basalts and lava channels...
, and marks the southern edge of this area of volcanic activity. This fissure vent was created when one or more magmatic dikes (sheets or tubes of magma cutting across the existing geologic features) found their way to the surface. At the northwestern edge of the lava field is a shield volcano
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
, with the fissure vent extending toward the southeast and the Hell's Half Acre site. Pit crater
Pit crater
A pit crater is a depression formed by a sinking of the ground surface lying above a void or empty chamber, rather than by the eruption of a volcano or lava vent. It is often found in chains or troughs. Several craters may merge into a linear alignment...
s and spatter cones follow this active fissure line. Two non-erupting fissures extend northwest from the shield volcano for about 2.7 miles (4.3 km). One scientific team hypothesized that the seven lava fields in the vicinity of Hell's Half Acre may belong to as few as two fissure vents.
Hell's Half Acre was created when basaltic pāhoehoe quickly flowed out of the volcanic rift. At least eight lava lobes have been identified by geologists. As magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
and volcanic gases drained from underneath the lava field, the field subsided—leaving behinds hummocks, or "hills" of lava (a feature which Hell's Half Acre retains today). There is evidence that lava filled and drained the lava lake numerous times, and that lava repeatedly overflowed the lake.
Lava from the fissure vent tended to flow downhill toward the southeast, covering part of the fissure. Lava tubes extend in a generally southeastern direction under the lava field, and surfaced in the far southeastern corner of the site. There is also evidence that later pāhoehoe lava lobes ran underneath or inside existing lobes, and then broke out.
The current name of the lava field was given to it by fur traders in the early 19th century seeking passage through the rough terrain of the Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
. The term "hell's half acre" was a commonly used expression to describe any rough land. One of the first white people to record their visit to Hell's Half Acre was Benjamin Bonneville
Benjamin Bonneville
Benjamin Louis Eulalie de Bonneville was a French-born officer in the United States Army, fur trapper, and explorer in the American West...
, a French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
-born United States Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
officer. Bonneville traveled west in 1832, on a leave of absence from the military. His expedition was financed by the wealthy fur trade
Fur trade
The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of world market for in the early modern period furs of boreal, polar and cold temperate mammalian animals have been the most valued...
r, John Jacob Astor
John Jacob Astor
John Jacob Astor , born Johann Jakob Astor, was a German-American business magnate and investor who was the first prominent member of the Astor family and the first multi-millionaire in the United States...
. Bonneville saw the site in 1833. The celebrated writer Washington Irving
Washington Irving
Washington Irving was an American author, essayist, biographer and historian of the early 19th century. He was best known for his short stories "The Legend of Sleepy Hollow" and "Rip Van Winkle", both of which appear in his book The Sketch Book of Geoffrey Crayon, Gent. His historical works...
used Bonneville's journals to write a book about the expedition, and based on his descriptions wrote about the area this way:
- Here occur some of the wild and striking phenomena of this wild and sublime region. The plain is gashed with numerous and dangerous chasms, from four to ten feet wide, and of great depth. Captain Bonneville attempted to sound some of these openings, but without any satisfactory results. A stone dropped into one of them reverberated against the sides for apparently a great depth.
In the late 19th century and early 20th century, the area was the center of logging activity. Red cedar
Thuja plicata
Thuja plicata, commonly called Western or pacific red cedar, giant or western arborvitae, giant cedar, or shinglewood, is a species of Thuja, an evergreen coniferous tree in the cypress family Cupressaceae native to western North America...
grew abundantly in the lava field, as the plant can grow directly on rock. In 1889, the village of Woodville (now a ghost town
Ghost town
A ghost town is an abandoned town or city. A town often becomes a ghost town because the economic activity that supported it has failed, or due to natural or human-caused disasters such as floods, government actions, uncontrolled lawlessness, war, or nuclear disasters...
) was founded near the Woodville Bend of the Snake River (near the modern town of Shelley, Idaho
Shelley, Idaho
Shelley is a city in Bingham County, Idaho, United States. The population was 3,813 at the 2000 census. The mascot for the city's high school is "King Russet", a russet-burbank potato that wears a crown, robe and scepter....
). The Woodville settlers harvested large amounts of red cedar for use as lumber and fuel. These practices were significantly cut back in the 1910s and 1920s as coal became more widely available as a fuel, but the harvesting of red cedar from Hell's Half Acre continued until 1942.
A wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
burned 500 acres (202.3 ha) of the site in 1999. In the fall of 2005, Michael Curtis Reynolds
Michael Curtis Reynolds
Michael Curtis Reynolds is an American who was convicted of terrorism-related crimes after a series of December 2005 online discussions with a US judge posing as a militant.-Biography:...
was arrested at the Hell's Half Acre rest area after the Federal Bureau of Investigation
Federal Bureau of Investigation
The Federal Bureau of Investigation is an agency of the United States Department of Justice that serves as both a federal criminal investigative body and an internal intelligence agency . The FBI has investigative jurisdiction over violations of more than 200 categories of federal crime...
lured him there with the promise of money and arms from a supporter. More recently, in 2006 the utility Utah Power
PacifiCorp
PacifiCorp is an electric power company in the northwestern United States.PacifiCorp has three primary subsidiaries:# Pacific Power is a regulated electric utility with service territory throughout Oregon, northern California, and southeastern Washington.# Rocky Mountain Power is a regulated...
tried to build an electrical substation
Electrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...
near the eastern-most part of Hell's Half Acre lava field.
External links
- Hell's Half Acre Web site at the U.S. Bureau of Land Management