Craters of the Moon National Monument

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Craters of the Moon National Monument
American quaking aspen in front of lava
American quaking aspen in front of lava
Craters of the Moon National Monument (USA)
Paris plan pointer b jms.svg
Coordinates: 43 ° 27'37 "  N , 113 ° 33'24.6"  W.
Location: Idaho , United States
Next city: Arco
Surface: 2,893.5 km²
Founding: May 2, 1924
Visitors: 227,179 (2008)
Snake River Plain with the lava fields of the sanctuary
Snake River Plain with the lava fields of the sanctuary
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The Craters of the Moon National Monument (since 2000 also Craters of the Moon National Monument and Preserve ) is a protected area of ​​the type of a national monument in the center of the Snake River plain in the US state of Idaho at about 1750 m above sea level. The area consists of large-scale cooled lava flows and some cinder cones . The volcanic activity has stopped, but has not stopped. The last eruption in the Craters-of-the-Moon area was about 2000 years ago.

Located in one of the most remote regions of the United States, the Craters of the Moon were not explored until the beginning of the 20th century and placed under protection in 1924. Previously expanded slightly several times, the area was expanded to 13 times the area in 2000. Since then, the entire volcanic field including the Wapi field in the south and the adjacent prairie areas have been protected. The extension areas are subject to the lower protection status of a National Preserve , which is why hunting is still permitted and the existing contracts for the use of the public areas by herds of private cattle ranchers remain in force. The reserve is jointly administered by the National Park Service and the Bureau of Land Management , two agencies under the umbrella of the US Department of the Interior .

The name of the protected area comes from the hostile impression that early visitors had. As part of the Apollo program , astronauts used the area briefly for training.

geology

Satellite image: The Craters of the Moon lava field, composed of individual lava flows, and the Wapi field southeast of it
Pahoehoe lava flow
Volcanic bomb
Indian Tunnel - inside lava tube

The Craters of the Moon area is located in the center of the volcanic plain of the Snake River , which runs through southern Idaho. Like the entire plain, it slopes gently and evenly to the south. Today's landscape and its geological subsoil were shaped in three characteristic phases.

Yellowstone hotspot

The subsoil of the plain is rhyolite tuff and rocks from compacted volcanic ash . They were created by a hotspot that was fed by a plume with magma from the earth's mantle . The North American Plate , one of the tectonic plates of the earth's crust , shifts over this plume , so that volcanic activity appears to be moving from southwest to northeast. The hotspot is now under the Yellowstone National Park and is responsible for the volcanic activity of the Yellowstone super volcano , its caldera , the geysers and the other volcanic manifestations of the national park.

Today's protected area was located over the hotspot around 11 million years ago. The magma rising from the earth's mantle melted granite rocks in the earth's crust . The surface of the earth bulged. A further increase in energy resulted in a catastrophic eruption and the melted granite was ejected in the form of rhyolite . A caldera and large layers of tuff and ash were created. With the apparent migration, the location of the next eruption shifted. 142 massive eruptions have been proven for the Snake River Plain, plus hundreds of medium-sized and smaller ones. The calderas typically overlap. In this way, rhyolitic lava and the ashes were ejected that now form the deep subsoil of the Snake River Plain. In the earth's crust, at a depth of at least 10 km, the melting processes of the hotspot left a layer of basaltic slag around 10–15 km thick , which to this day is largely in a molten state. Since then, it has provided the energy for volcanic activity in the region. After cooling, the surface subsided, resulting in a subsidence that marks the migration path of the North American Plate across the hotspot: the lowlands of the Snake River Plain.

Basaltic eruptions

Around six million years ago, a tectonic process began in western North America that led to the expansion of the earth's crust, which resulted in a large number of largely parallel rift fractures running roughly in a north-south direction . At that time arose Basin-and-Range region with their parallel ditch -and- Horst structures that of Mexico is just enough in the south to the north still to Idaho. In the south of what is now Idaho, the forces acted on the sunken layers of eruptive rock on the migration path to the hotspot. Here, the stretching of the crust led to a large number of stretch fractures in a northwest-southeast orientation. The largest of the parallel elongation fractures lies in the center of the plain, is around 80 km long and 2.5 km wide, and is known as the Great Rift (of Idaho) . According to other interpretations, the Great Rift was created under the pressure of rising lava from the reservoir, which was plastically deformed by loading from above, creating cracks in the process.

In the Great Rift , as in the other fractures in the Snake River Plain, basaltic magma rose in Dykes and emerged on the surface in the form of fissure volcanoes , cinder cones and shallow shield volcanoes . In the period from around 6 million years ago to around 15,000 years ago, enormous lava flows formed, which formed several layers up to 1200 m thick in the center of the Snake River Plain, in which individual layers of sedimentary rock are embedded. They cover about 95% of the plain.

Recent activities

The last phase of volcanic activity in the Crater of the Moon area began about 15,000 years ago. At the Great Rift , three and five more young lava fields emerged. The three fields of the Great Rift, Craters of the Moon , Kings Bowl and Wapi , lie within the reserve. It is named after the Craters of the Moon field, which is the largest lava field in the Snake River Plain and at the same time in the Continental United States , most of which dates from the Holocene , i.e. the last 10,000 years. It is composed of over 60 individual lava flows that overlap one another. Around 30 km³ of basaltic lava emerged in eight eruptive periods and cover a combined area of ​​around 1,600 km².

Around 80% of the lava fields consist of the low- viscosity Pāhoehoe lava . In solidified form, it is characterized by smooth surfaces and round shapes, which occasionally can take on a blue or green sheen. It is fed by long rivers which, when they run out and cool , can leave hollow lava tubes , elongated caves in and under the lava flows. Five lava tubes can be climbed in the area. The rest of the lava fields are made up of the irregular Aa lava . It has a sharp-edged surface, which is composed of individual chunks from less than one to a few centimeters in size. Their shape is partially undulating with up to 3 m high mountain and valley structures. Their limits are usually marked by a steep front.

Geochemically , the basaltic lava flows in the Craters of the Moon field consist of olivine tholeiite . They are particularly rich in iron , phosphorus , titanium and alkali metals

In addition to the lava flows, around 25 cinder cones were thrown up during the eruptions, which were often created by several nearby chimneys , so that the cones overlap or lie completely inside one another. In addition, volcanic bombs of various types and sizes were released. The flowing lava formed several shallow shield volcanoes, including the Wapi field, which was created from just one eruption.

The most recent appearances are smaller lava flows to the north of the Craters of the Moon field. Among them is the North Crater Flow , which has been dated to around 2000 years old. Even if the volcanic activity in the Craters of the Moon area has stopped since then, it has not ceased.

Kipukas , islands of weathered lava surrounded by younger lava flows
Feather grass in front of lava blocks in Devils Orchard

Ecosystems

The area of ​​the Craters of the Moon lies in the area of ​​the Eastern Snake River Basalt Plain. The climate is semi-arid , continental with hot, dry summers and cold winters. The soils are young and the humus layer is low where available . A distinction must be made between three types of soil: the young lava fields, areas of older lava flows in which soil formation has already taken place, and soils on Aeolian sediments of sand and loess that are transported by wind . The small-scale mosaic of habitats is specific to the protected area - and atypical for the region. Several hundred kipukas , medium-sized and small islands of weathered soils are embedded in younger lava rivers and each form self-contained ecosystems.

The young lava areas are mostly without any vegetation. There are tufts of feather grass here and there . Various species grow in crevices and cracks and endure extreme drought. Among them are the beard thread species Penstemon deustus , the flaming flower Phlox hoodii , the herbaceous plant Aliciella leptomeria and finger herbs . At the volcanic cones and some hill flanks there is enough local water for montane bush and forest communities. Juniper , American trembling aspen and Nevada stone pine ( Pinus flexilis ) grow here .

On weathered lava fields, the typical plant community is a desert sagebrush steppe. The sagebrush, which gives it its name, forms large areas of low bushes, otherwise the ground is loosely covered with grasses from the prairie . The most common type of grass is the blue tuft wheatgrass ( Agropyron spicatum - also: Pseudoroegnaria spicata ), which grows in clusters. There are also various feather grasses and Indian rice grass ( Oryzopsis hymenoides ). Purshia tridentata is a common shrub. The roof brim appears as a neophyte .

The same plant communities cover the soils outside the lava fields. The vegetation is denser, which is why the areas are used for extensive pasture use with cattle . The prairies in the center and south of the area are severely disturbed by historical and ongoing grazing.

The animal world is characterized by the great drought and the extreme summer temperatures. Different animals adapt through a nocturnal way of life. These include pocket rats , skunk , red fox , bobcat , puma , several species of bats , night swallows , owls and most small rodents . Mule deer , coyote , tree prick and cottontail rabbits as well as many songbirds use the day's edge . Ground squirrels , chipmunks , marmots , as well as lizards , snakes , eagles and buzzards are active during the day . Some species of beetles that are endemic to the area live in the lava tubes .

history

Goodale's cutoff in the mugwort steppe today
The Apollo 14 team in the protected area (with autographs)
Echo Crater in the hinterland designated as a wilderness area

Originally the Snake River Plain was sparsely populated by Shoshonen . However, the lava fields and the other volcanic structures of the Great Rift were hostile to life and were not used permanently. Stones were artificially placed around the tunnel opening on a lava tube, which is now called the Indian Tunnel .

The Lewis and Clark expedition of 1805/6 brought the first whites to what is now Idaho, but they passed the area north of today's sanctuary. In the 1830s, the Snake River area was frequented by trappers and fur traders from the British Hudson's Bay Company . They probably never came to today's protected area either. In 1833, US officer Benjamin Bonneville explored the Snake River and parts of the plain. The first proven stay of a white man in today's protected area took place in 1852. John Jeffrey explored a northern shortcut for the Settler Trek on the Oregon Trail to avoid the wide loops of the Snake River. His route led through the extreme northwest of what is now the National Monument. It was only used sporadically in the first few years, but gained in importance in 1862 when the Shoshone and Bannock Indians defended themselves on the main route on the Snake River against the white people invading their country. To avoid the Indians, the largest settler train on the Oregon Trail of all time with 338 wagons and 1095 people was led by Tim Goodale over the northern route, which from then on was referred to and preferred as the Goodale Cutoff .

In 1901 the area was first inspected by a geologist from the US Geological Survey . Harold Stearns, USGS geologist, visited the area in 1921 and 1923 and wrote an initial description which was published in the 1924 Geographical Review . The National Park Service requested an expert opinion from him, which should contain the area structures and suitable boundaries of a possible National Monument. In 1920 Robert W. Limbert and his neighbor WL Cole, nature lovers from Boise , hiked through the Great Rift area in 17 days. They were the first to explore the region in full length and describe the diverse volcanic structures. Limbert published a report on the expedition in the popular National Geographic magazine in 1924 under the title "Among the 'Craters of the Moon'". He suggested designating the area as a national park and sent his sketchbook with photos and other notes to President Calvin Coolidge . Based on the present report for the National Park Service and the public awareness of the area after the publication of the National Geographic article, Coolidge used the authorization of the Antiquity Act and dedicated the area as a National Monument.

In the first decades, the protected area was only slightly expanded. In preparation for the 50th anniversary of the National Park Service , the Mission 66 program was launched in the mid-1950s, investing around one billion dollars in national parks and other federal protected areas. From 1956, Craters of the Moon also got a new visitor center, a campsite, a road running in a circle through the protected area and other facilities for nature and cultural interpretation and visitor care.

In 1969, teams from the Apollo program explored geological regions in the western United States. Astronauts Alan Shepard , Edgar Mitchell , Eugene Cernan and Joe Engle came to the Crater of the Moon area , among others, and learned how to expertly identify and describe volcanic rock as would be expected on the moon.

In 1970, the United States Congress dedicated most of the National Monument to the Wilderness Area , the strictest class of wildlife sanctuary in the United States. It was the first officially protected wilderness in a National Park Service area.

In the 1980s, local tourism entrepreneurs and Idaho state politics moved the National Monument to a national park. They hoped that this would create a stronger attraction for tourism in the region. Idaho is the only state in the western United States that does not have a national park within its borders, apart from a narrow strip on the edge of Yellowstone National Park . The National Park Service rejected the upgrade: The area would only have one type of natural manifestation with volcanism and would therefore not be suitable as a national park. National Monument status would be appropriate. At the beginning of the 1990s, a mediating position was worked out, according to which it should remain with the designation as a national monument, but the area could be expanded over a large area.

In 2000 the reserve was expanded to include the entire lava fields of the Great Rift area and neighboring prairie areas were added under the administration of the Bureau of Land Management. The protected area under the name Crater of the Moon National Monument and Preserve now covers nearly 2900 km² and all volcanic phenomena in the region.

The reserve today

North Crater in winter (view from visitor center)
Schematic map of the developed area
Schematic map of the administrative responsibilities in the protected area

The developed area of ​​the Craters of the Moon National Monument and Preserve is located in the north of the entire area on US Highway US-20 , which is bundled with US-26 and US-93 . A spur road branches off from the highway to the visitor center, it continues to the small campsite and a one-way street, about 11 km long loop, which leads through the north of the most important lava field. The car route winds around several volcanic cones, from which branch roads branch off, which lead to designated short hiking trails.

The most popular are the North Crater Flow Trail at the visitor center, which introduces the characteristics of a lava landscape, the Devils Orchard Trail , where visitors can explore the slow settlement of the lava landscape with pioneer vegetation , and the Caves Trail , which is accessible to visitors at the entrances of four and a viewable lava tube leads. The full length of almost 250 m of the Indian Tunnel can be entered without further equipment, the others require cave equipment with several independent light sources and the willingness to crawl through narrow entrances. There are also two designated hiking trails that lead from the developed part of the area into the wilderness region. In the summer half-year, the rangers offer daily guided hikes and lectures. In winter, the road loop is closed to cars and is open as a cross - country ski trail . Guided tours on snowshoes take place on the weekends.

Craters of the Moon National Monument and Preserve is the most important tourist destination in the sparsely populated region with well over 200,000 visitors a year. However, it is typically only a detour for visitors to other destinations in the wider area and is only targeted by around 20% of visitors. The others come to Idaho for other reasons or just traverse the region and use the sanctuary as a stopover.

Almost all visitors restrict themselves to the developed area in the north, which however only makes up the smallest part of the protected area. It is located in the original National Monument , which has an area of ​​about 216 km². Since the expansion in 2000, the area has extended south to almost the entire width of the Snake River Plain. At that time, around 1,600 km² were added as a National Preserve under the administration of the National Park Service . These are almost exclusively lava fields. Another 1000 km² are under the administration of the Bureau of Land Management and were also added to the protected area in 2000. They are steppe and the existing pasture use by herds of cattle from private ranchers was retained in the designation of the protected area. In the hinterland there are a few unpaved roads and slopes in the steppes, the lava fields can only be moved on foot.

literature

  • Kathleen M. Haller; Spencer H. Wood: Geological field trips in southern Idaho, eastern Oregon, and northern Nevada . Boise, Idaho, Boise State University, 2004, ISBN 978-0-9753738-0-4

Web links

Commons : Craters of the Moon National Monument  - Collection of Images, Videos, and Audio Files

Individual evidence

  1. Unless otherwise stated, this chapter is based on: Sonja Melander: Geology of Craters of the Moon. National Park Service, 2013
  2. National Park Service: Craters of the Moon - Geologic Activity (accessed April 17, 2009)
  3. ^ A b Idaho State University: Idaho Geology Web Course - Module: Neogene Snake River Plain-Yellowstone Volcanic Province
  4. ^ Robert Baer Smith, Lee J. Siegel: Windows into the earth: the geologic story of Yellowstone and Grand Teton. Oxford University Press, 2000. ISBN 0-19-510597-4 , page 45 in Google Book Search
  5. Scott S. Hughes, Richard P. Smith, et al .: Mafic Volcanism and Environmental Geology of the Eastern Snake River Plain, Idaho (PDF; 2.4 MB) . In: Scott S. Hughes, Glenn D. Thackray (Eds.): Guidebook to the Geology of Eastern Idaho , Idaho Museum of Natural History, 1999, ISBN 0-937834-64-5 , pages 143-168
  6. ^ Mel A. Kuntz, Duane E. Champion, Richard H. Lefebre: Geology of the Craters of the Moon lava field, Idaho . In: Geological Society of America, Centennial Field Guide - Rocky Mountain Section , Volume 2. Boulder, Colorado, Geological Society of America, 1987, ISBN 0-8137-5406-2 , pages 123-126
  7. This chapter refers to the description of the Class IV ecosystems: Environmental Protection Agency: Ecoregions of Idaho - Front and Ecoregions of Idaho - Back .
  8. The description of the plant communities is largely based on: Jack Bell, Dan Cogan et al .: Vegetation Inventory Project - Craters of the Moon National Monument and Preserve Natural Resource Technical Report NPS / UCBN / NRTR — 2009/277. National Park Service, Fort Collins, Colorado.
  9. ^ National Park Service: Craters of the Moon - Animals
  10. This chapter is based on National Park Service: Craters of the Moon - Timeline (accessed December 21, 2009) unless otherwise stated
  11. Craters of the Moon Natural History Association: Goodale Cutoff (accessed December 21, 2009)
  12. ^ Douglass E. Owen, Sonja M. Melander: Geology of Craters of the Moon . National Park Service, 2013
  13. ^ National Park Service: Craters of the Moon - Robert Limbert (accessed December 21, 2009)
  14. National Park Service: Craters of the Moon - Astronauts (accessed January 26, 2010)
  15. The Wilderness Society: Craters of the Moon and the Great Rift - A long history of Expansion ( Memento from July 15, 2007 in the Internet Archive )
  16. ^ Daniel J. Stynes: Impacts of Visitor Spending on the Local Economy: Craters of the Moon National Monument and Preserve, 2004. Michigan State University (accessed December 23, 2015)
This version was added to the list of articles worth reading on February 22, 2010 .