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America's Volcanic Past
Craters of the Moon National Monument

"Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994
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Select Volcanic Highlights and Features:
[NOTE: This list is just a sample of various Craters of the Moon features or events and is by no means inclusive. All information presented here was gathered from other online websites and each excerpt is attributed back to the original source. Please use those sources in referencing any information on this webpage, and please visit those websites for more information on the Geology of the Craters of the Moon.]

  • Craters of the Moon
  • Craters of the Moon Lava Field
  • Craters of the Moon National Monument
    • Big Cinder Butte
    • Big Craters
    • Devil's Orchard
    • Great Rift
    • MORE Great Rift
    • Highway Flow
    • Indian Tunnel
    • Inferno Cone
    • King's Bowl
    • North Crater
    • Picabo Volcanic Field
    • Sunset and Grassy Cones
    • Wapi
  • Snake River Plain
  • MORE America's Volcanic Past - Idaho

Craters of the Moon

Craters of the Moon Lava Field:
Craters of the Moon National Monument, Idaho, U.S.A. Craters of the Moon National Monument and surrounding lava flows, are located along the northern border of the Snake River Plain This showcase of volcanic formations, including lava flows, cinder cones, and craters, was created by a fissure about 50 miles (80 kilometers) long in the Earth's crust. Through this zone of weakness, known as the Great Rift, lava frequently welled up to the surface over thousands of years. With each successive series of eruptions, older volcanic formations were buried, and new ones were superimposed on their surfaces. The barren black lava flows were emitted during the most recent eruptions, which occurred approximately 2,000 years ago.




Excerpt from: NASA "Earth From Space" Website, 2002
   


Craters of the Moon Lava Field

Craters of the Moon Lava Field:4
The Craters of the Moon Lava Field is the largest basaltic, dominantly Holocene (last 10,000 years) lava field in the conterminous United States. Volcanic eruptions first occurred at Craters of the Moon about 15,000 years ago. The most recent eruptions ended about 2,100 years ago and were likely witnessed by the Shoshone people. A Shoshone legend speaks of a serpent on a mountain who, angered by lightening, coiled around and squeezed the mountain until liquid rock flowed, fire shot from cracks, and the mountain exploded. The volcanic area now lies dormant, but its eight eruptive periods formed 60 lava flows which traveled as far as 45 miles from their vents. Some of the lava flowed around areas of higher ground, forming isolated islands of vegetation called "kipukas". Today, these kipukas provide a window on the vegetation communities of the past. They contain some of the last pristine vegetation in the Snake River Plain, including 700-year-old juniper trees and relic stands of sagebrush and native bunchgrass.




Craters of the Moon National Monument

Craters of the Moon National Monument1
Established in 1924, Craters of the Moon National Monument celebrated its 75th birthday in 1999. On November 9, 2000, President Clinton issued a proclamation greatly expanding the size of the monument. The expanded monument will be managed cooperatively by the National Park Service and the Bureau of Land Management. The monument encompasses three major lava fields and the surrounding sagebrush steppe grasslands. The Craters of the Moon lava field covers 618 square miles and is the largest young basaltic lava field in the conterminous United States. The park contains more than 25 volcanic cones including outstanding examples of spatter cones. Sixty lava flows lie within the Craters of the Moon lava field ranging in age from 15,000 to just 2,000 years old. The Kings Bowl and Wapi lava fields, which are about 2,200 years old, are now part of the monument. All three lava fields lie along the Great Rift, with some of the best examples of open rift cracks in the world. There are excellent examples of pahoehoe, slabby pahoehoe, shelly pahoehoe, spiny pahoehoe, aa, and block lava, as well as rafted blocks, tree molds, lava tubes, and many other volcanic features. Although a desolate looking place at first glance, the Monument thrives with wildlife. A 7 mile loop drive at the north end of the Monument provides unique views and hiking opportunities.

Big Cinder Butte:2
Big Cinder Butte - the highest cone within the monument - has a total volume of 2 x 108 cubic meters and rises 250 meters above the plain. It has no summit crater. Many bombs are found on the cone, including cow dung, breadcrust, and spindle types. The rims of five or six older volcanoes are visible around its base. Several flows issued from Big Cinder Butte. The youngest originated from a fissure on the north side of the cone and is a "Blue Dragon" types pahoehoe flow. This type of flow is characterized by a shining iridescent surface.

Big Craters:2
Big Craters is a series of spatter cones and open fissure flows. The slope of each cone is 50 to 60 degrees near the summit and decreases to approximately 30 degrees near the base. The upper slopes are angular and rough, but the lower slopes are smoother and have profiles similar to those of cinder cones. The cones range in height from 12 to 20 meters and have chimneylike vent areas, most of which have collapsed, displaying a rubbly interior. Toward the northwest portion of the Big Crater area, however, two vents remain intact. Several large pahoehoe and aa flows were erupted from these vents.

Devil's Orchard:1
After the road skirts Paisley Cone, on the east side stands Devils Orchard. This group of lava fragments stands like islands in a sea of cinders. A short spur road leads to a self-guiding trail through these weird features. As you walk this 1/2-mile trail, you will see how people have had an impact on this lava landscape and what is being done to protect it today. This barrier-free trail is designed to provide access to all people.

Great Rift:4
The monument's central focus is the Great Rift, a 62-mile long crack in the earth's crust. The Great Rift is the source of a remarkably preserved volcanic landscape with an array of exceptional features. Craters, cinder cones, lava tubes, deep cracks, and vast lava fields form a strangely beautiful volcanic sea on central Idaho's Snake River Plain.

MORE Great Rift:5
The Great Rift volcanic rift zone is a zone of cracks running approximately northwest to southeast across almost the entire eastern part of the Snake River Plain. The entire Great Rift is 62 miles long. The Great Rift is an example of basaltic fissure eruption. This type of volcanic activity is characterized by extrusion of lavas from fissures or vents that is relatively quiet in comparison with highly explosive eruptions such as the 1980 Mount Saint Helens eruption. Where the Great Rift intersects the earth's surface, there is an array of cinder cones, lava cones, eruptive fissures, fresh-appearing lava flows, noneruptive fissures, and shield volcanoes.

Highway Flow:2
The North Crater flow possesses features termed "monoliths" which appear to be fragments of cinder cones broken apart and rafted to their present positions by flowing lava. They range in length from about 1/2 to 200 meters long; some are up to 25 meters high. The massive Highway flow issued northward from North Crater vent and was confined to the valley between Sunset and Grassy Cones.

Indian Tunnel:2
Indian Tunnel is one of the largest lava tubes in the Monument, reaching widths of over 15 meters. Concentric rock heaps in this area were probably used to secure tepees of the Indians who frequented the caves. Numerous other tunnels and caves are common in this area, ranging from centimeters to meters in size.

Inferno Cone:2
The area east of Inferno Cone consists of a series of lava "domes". Many of the flow unites contain lava tubes, and individual flow units are generally "Blue Dragon" pahoehoe. The lava tubes in this area may be part of an extensive network in a single flow. Indian Tunnel is one of the largest tubes in the Monument. [See Indian Tunnel above]

King's Bowl:3
Composite flow field; Basalt composition; 1,500 meter elevation. The King's Bowl Field is small and cover less than 2.6 square kilometers. It is situated on the King's Bowl Rift Set, one of several such sets which collectively make up Idaho's Great Rift, a series of tension fractures that cross cut the eastern Snake River Plain. The King's Bowl field is a composite feature made up of flows from several point sources along the Rift as well as a larger, apparently dike-fed sheet flow, which for a time was held in a lava lake. These flows locally overlap, indicating that the eruptive sequence was complex and issued from different vents at different times.

North Crater:2
The North Crater flow possesses features termed "monoliths" which appear to be fragments of cinder cones broken apart and rafted to their present positions by flowing lava. They range in length from about 1/2 to 200 meters long; some are up to 25 meters high. The massive Highway flow issued northward from North Crater vent and was confined to the valley between Sunset and Grassy Cones.

Picabo Volcanic Field:4
Craters of the Moon is in the Picabo Volcanic Field.

Sunset and Grassy Cones:2
Sunset and Grassy cones rise approximately 160 meters above the surrounding plain. Three flows issued from Sunset cone but are largely blanketed with ash and soil. Two pahoehoe flows breached the crater in the northeast and in the west. On the northwest flank of the crater, an aa flow, approximately 6 meters thick issued from a small parasitic cone. Both cones represent some of the earliest eruptive activity in the Monument. Two craters on the north side of Grassy Cone erupted lava simultaneously to produce flows which merged and extended northward. A network of lava tubes, some as large as 5 meters in diameter, developed within the flows.

Wapi:2
The Wapi lava field is one of several Holocene to Pleistocene volcanic fields on the Snake River Plain. In many respects, it is typical of the older fields of low shields that make up the present surface of the plain. It covers a large (300 square kilometer) area that is elongate in the north-south direction and has three prominent lobes extending east, west, and northwest from the main mass of the field.




Snake River Plain

Snake River Plain:1
Craters of the Moon lies at the north edge of the eastern Snake River Plain, a broad flat arc, concave to the north, which covers nearly 10,000 square miles of southern Idaho. It extends from the Yellowstone Plateau and the Teton Mountains on the east to the Oregon state line on the west. The Snake River borders the southern edge of the plain, which occupies almost a quarter of the surface of Idaho and contrasts markedly with the mountainous terrain that dominates the northern, central, and far southern parts of the state. The eastern Snake River Plain is essentially flat in this vicinity: vertical relief is a few hundred feet at Craters of the Moon and less than that elsewhere.




MORE America's Volcanic Past - Idaho





Excerpts from:
1) U.S. National Park Service Website, Craters of the Moon National Monument, 2000
2) Greeley, 1990, IN: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada: Cambridge University Press, 354p
3) King, 1990, IN: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada: Cambridge University Press, 354p
4) U.S. Bureau of Land Management, Idaho Office, Website, 2001
5) NASA "Earth From Space" Website, 2002

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08/07/02, Lyn Topinka