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Yellowstone National Park is a U.S. National Park located in the western states of Wyoming, Montana, and Idaho. Yellowstone is the first and oldest national park in the world and covers 3,845 square miles (8879 km²), mostly in the northwest corner of Wyoming. The park is famous for its various geysers, hot springs, supervolcano and other geothermal features and is home to grizzly bears, wolves, and free-ranging herds of bison and elk. It is the core of the Greater Yellowstone Ecosystem, one of the largest intact temperate zone ecosystems remaining on the planet. The world's most famous geyser, the Old Faithful Geyser, is also located in Yellowstone National Park.

Long before any recorded human history in Yellowstone, a massive volcanic eruption spewed an immense volume of ash that covered all of the western U.S., much of the midwestern U.S., northern Mexico and some areas of the Pacific Coast. The eruption dwarfed that of Mount St. Helens in 1980 and left a huge caldera 43 miles by 18 miles (70 km by 30 km) sitting over a huge magma chamber (see Geology section and Yellowstone Caldera). Yellowstone has registered three major volcanic eruption events in the last 2.2 million years with the last event occurring 640,000 years ago. Its eruptions are the largest known to have occurred on Earth within that timeframe, producing drastic climate change in the aftermath (See also:Supervolcano).

The park received its name from its location at the headwaters of the Yellowstone River. French trappers gave this river the name "Roche Jaune," probably a translation of the Hidatsa name "Mi tsi a-da-zi," and the later American trappers rendered the French name into English as "Yellow Stone." Although it is commonly believed that the river was named for the yellow rocks seen in the Grand Canyon of the Yellowstone, the Native American source name more likely derived from the yellowish bluffs located near present-day Billings, Montana.

Forest fires

A series of lightning-derived fires started to burn large portions of the park in July of the especially dry summer of 1988. Thousands of firefighters responded to the blaze in order to prevent human-bult stuctures from succumbing to the flames. Controversially, however, no serious effort was made to completely extinguish the fires, and they burned until the arrival of autumn rains. Ecologists argue that fire is part of the Yellowstone ecosystem, and that not allowing the fires to run their course (as has been the practice in the past) will result in an overgrown forest that would be extremely vulnerable to deoxygenation, disease, and decay. In fact, relatively few megafauna in the park were killed by the fires; and since the blaze, many saplings have sprung up on their own, old vistas are viewable once again, and may previously unknown archaeological and geological sites of interest were found and cataloged by scientists. The Natioal Park Srvice now has a policy of lighting smaller, controlled "prscribed fires" to prevent another dangerous buildup of flammable materials.

Geography

The Continental Divide of North America runs roughly diagonally through the southwestern part of the park. The divide is a topographic ridgeline that bisects the continent between Pacific Ocean and Atlantic Ocean water drainages (the drainage from one-third of the park is on the Pacific side of this divide).

For example, the Yellowstone River and the Snake River both have their origin close to each other in the park. However, the headwaters of the Snake River are on the west side of the continental divide, and the headwaters of the Yellowstone River are on the east side of that divide. The result is that the waters of the Snake River head toward the Pacific Ocean, and the waters of the Yellowstone head for the Atlantic Ocean (via the Gulf of Mexico).

The park sits on a high plateau which is, on average, 8,000 feet (2,400 m) above sea level and is bounded on nearly all sides by mountain ranges of the Middle Rocky Mountains, which range from 10,000 to 14,000 feet (3,000 to 4,300 m) in elevation. These ranges are: the Gallatin Range (to the northwest), Beartooth Mountains (to the north), Absaroka Mountains (to the east), Wind River Range (southeast corner), Teton Mountains (to the south, see Grand Teton National Park) and the Madison Range (to the west). The most prominent summit in the plateau is Mount Washburn at 10,243 feet (3,122 m).

Just outside of the southwestern park border is the Island Park Caldera, which is a plateau ringed by low hills. Beyond that are the Snake River Plains of southern Idaho, which are covered by flood basalts and slope gently to the southwest (see Craters of the Moon National Monument).

The major feature of the Yellowstone Plateau is the Yellowstone Caldera; a very large caldera which has been nearly filled-in with volcanic debris and measures 30 by 40 miles (50 by 60 km). Within this caldera lies most of Yellowstone Lake, which is the largest high-elevation lake in North America, and two resurgent domes, which are areas that are uplifting at a slightly faster rate than the rest of the plateau.

Geology

Yellowstone is at the northeast tip of a smooth U-shaped curve through the mountains, which is now the Snake River Plain. This curved plain was created as the North American continent drifted across a stationary volcanic hotspot beneath the Earth's crust. This hot spot used to be near what is now Boise, Idaho, but North America has drifted at a rate of 45 mm a year in a southwestern direction, shifting the hot spot to its present location.

Yellowstone Caldera is the largest volcanic system in North America. It has been termed a "supervolcano" because the caldera was formed by exceptionally large explosive eruptions. It was created by a cataclysmic eruption that occurred 640,000 years ago that released 1,000 cubic kilometers of ash, rock and pyroclastic materials (this was 450 times larger than Mount St. Helens' 1980 eruption), forming a crater nearly a kilometre deep and 30 by 70 kilometres in area (18 by 43 mi) (the size of the caldera has been modified a bit since this time and has mostly been filled in, however). The welded tuff geologic formation created by this eruption is called the Lava Creek Tuff. In addition to the last great eruptive cycle there were two other previous ones in the Yellowstone area.

Each eruption is in fact a part of an eruptive cycle that climaxes with the collapse of the roof of a partially emptied magma chamber. This creates a crater, called a caldera, and releases vast amounts of volcanic material (usually through fissures that ring the caldera). The time between the last three cataclysmic eruptions in the Yellowstone area has ranged from 600,000 to 900,000 years, but the small number of such climax eruptions can not be used to make a prediction for the time range for the next climax eruption.

The first and largest eruption climaxed to the southwest of the current park boundaries 2.2 million years ago and formed a caldera about 50 by 80 kilometres in area (30 by 50 mi) and hundreds of meters deep after releasing 2,500 cubic kilometers of material (mostly ash, pumice and other pyroclastics). This caldera has been filled in by subsequent eruptions, and the geologic formation created by this eruption is called the Huckleberry Ridge Tuff.

The second eruption, at 280 km³ of material ejected, climaxed 1.2 million years ago and formed the much smaller Island Park Caldera and the geologic formation called the Mesa Falls Tuff. All three climax eruptions released vast amounts of ash that blanketed much of central North America and fell many hundreds of miles away (as far as California to the southwest; see Lake Tecopa). The amount of ash and gases released into the atmosphere probably caused significant impacts to world weather patterns and led to the extinction of many species in at least North America. About 160,000 years ago a much smaller climax eruption occurred which formed a relatively small caldera that is now filled in with the West Thumb of Yellowstone Lake.

Lava strata is most easily seen at the Grand Canyon of the Yellowstone where the Yellowstone River continues to carve into the ancient lava flows. According to Ken Pierce, U.S. Geological Survey geologist, at the end of the last glacial period, about 14,000 to 18,000 years ago, ice dams formed at the mouth of Yellowstone Lake. When the ice dams melted, a great volume of water was released downstream causing massive flash floods and immediate and catastrophic erosion of the present-day canyon. These flash floods probably happened more than once. The canyon is a classic V-shaped valley, indicative of river-type erosion rather than glaciation. Today the canyon is still being eroded by the Yellowstone River.

After the last major climax eruption 630,000 years ago until about 70,000 years ago, Yellowstone Caldera was nearly filled in with periodic eruptions of rhyolitic lavas (example at Obsidian Cliffs) and basaltic lavas (example at Sheepeaters Cliff). But 150,000 years ago the floor of the plateau began to bulge up again. Two areas in particular at the foci of the elliptically shaped caldera are rising faster than the rest of the plateau. This differential in uplift has created two resurgent domes (Sour Creek dome and Mallard Lake dome) which are uplifting at 15 millimeters a year while the rest of the caldera area of the plateau is uplifting at 12.5 millimeters a year.

Preserved within Yellowstone are many geothermal features and some 10,000 hot springs and geysers, 62% of the planet's known total. The superheated water that sustains these features comes from the same hot spot described above.

The most famous geyser in the park, and perhaps the world, is Old Faithful Geyser (located in Upper Geyser Basin), but the park also contains the largest active geyser in the world, Steamboat Geyser in the Norris Geyser Basin.

In 2003 changes at the Norris Geyser Basin resulted in the temporary closure of some trails in the basin. This coincided with the release of reports about a multiple year USGS research project mapping the bottom of Yellowstone Lake that identified a structural dome that had uplifted at some time in past beneath Yellowstone Lake. On March 10, 2004, a biologist discovered 5 dead bison which apparently had inhaled toxic geothermal gases trapped in the Norris Geyser Basin by a seasonal atmospheric inversion. Shortly after, in April 2004, the park experienced an upsurge of earthquake activity. These events inspired a great deal of media attention and speculation about the geologic future of the region. The United States government responded by allocating more resources to monitor the volcano and reminding visitors to remain on designated safe trails. The intervals between the historic large, caldera-forming explosions suggest that another such explosion may be "due," if not overdue.

Biology and ecology

The dominant tree species in the park is Lodgepole pine, however, varieties of spruce, fir and aspen are also common. There are at least 600 species of trees and plants found in the park, some of which are found nowhere else.

Yellowstone is widely considered to be the finest megafauna wildlife habitat in the lower 48 states. Animals found in the park include the majestic American bison (buffalo), grizzly bear, black bear, elk, moose, mule deer, pronghorn, bighorn sheep and mountain lion (puma). Rivers in the Yellowstone drainage comprise the core range of the cutthroat trout subspecies known as Yellowstone cutthroat trout, a fish highly sought by anglers yet one that has faced several threats in recent years, including the illegal intentional introduction of lake trout, which consume the smaller cutthroat trout; the ongoing drought; and the accidental introduction of a parasite which causes a terminal nervous system disease in younger fish, known as whirling disease.

The relatively large bison populations that exist in the park are a concern for ranchers who fear that the bison can transmit bovine diseases to their domesticated cousins. In fact, about half of Yellowstone's bison have been exposed to brucellosis, a bacterial disease that came to North America with European cattle and may cause cattle to miscarry. The disease has little effect on park bison and no reported case of transmission from wild bison to a visitor or to domestic livestock has ever been filed. But since the possibility of contagion still exists, the State of Montana believes its "brucellosis-free" status may be jeopardized if bison are in proximity to cattle. Montana had approved a bison hunt for the fall of 2005, with 50 licenses issued to shoot bison that have left the park. Elk also carry the disease, but this popular game species is not considered a threat to livestock.

To combat the perceived threat, National Park personnel regularly harass bison herds back into the park when they venture outside of park borders. Animal rights activists state that is a cruel practice and that the possibility for disease transmission is not as great as some ranchers maintain. Ecologists also point out that the bison are just traveling to seasonal grazing areas that lie within the Greater Yellowstone Ecosystem that have been converted to cattle grazing (most of these areas are also within United States National Forests).

After the wolves were extirpated from Yellowstone, the smaller cousin of the wolf, the coyote, then became the park's top predator. However, the coyote is not able to bring down any large animal in the park and the result of this lack of a top predator on these populations was a marked increase in lame and sick megafauna.

Starting in 1918, in an effort to protect elk populations, the Director of the Park Service ordered “extermination of mountain lions and other predatory animals” in Yellowstone. Park Service hunters carried out these orders and by 1926 they had killed 122 wolves. By this time wolves were all but eliminated from Yellowstone.

By the 1990s, the Federal government had reversed its views on wolves. In a controversial decision by the U.S. Fish and Wildlife Service (which oversees threatened and endangered species), wolves were reintroduced into the park. Before 1994 there were no wolves in Yellowstone. The wolves that were reintroduced in 1995 and 1996 thrived and there are now over 300 of their descendents living in the Greater Yellowstone Area.

However, ranchers in surrounding areas are concerned about wolves that venture outside the park and prey on their livestock, especially sheep and cattle. For the most part, wolves kill what they were taught to kill as pups, so they tend to prey on elk rather than sheep, but once a wolf pack begins eating sheep and training the pups to eat sheep, there is little recourse but to destroy the offending pack members. Ranchers are compensated for their losses if they can prove that wolves killed the livestock, but they contend that it is often difficult to prove that the kills were not made by coyotes or wild dogs.

Reintroduced wolf packs do not carry endangered species status, so ranchers can kill wolves that threaten their herds, but wolves relocating from Canada on their own have begun to merge with the Yellowstone population, making it difficult to discern which wolves are protected and which are not.

The National Park Service was generally not in favor of the reintroduction, citing evidence that wolves had already begun to return on their own, reestablishing themselves in very limited numbers prior to the wolf reintroduction. Wildlife biologists employed by the National Park Service had documented rare sightings made personally and from eyewitness accounts. It was a quiet concern that the compact agreed on by federal agencies and the states in which Yellowstone is located would ultimately provide less protection to the wolf, because the threatened status would be amended to appease local interests such as ranchers who would not likely face prosecution under the reintroduction agreement.

In Yellowstone's hot waters, bacteria form mats consisting of trillions of individual bacteria. The surfaces of these mats assume bizarre shapes, and flies and other arthropods live on the mats, even in the midst of the bitterly cold winters. Scientists thought that microbes there gained sustenance only from sulfur, but scientists from the University of Colorado at Boulder discovered in 2005 that the sustenance for some species is molecular hydrogen - although there is evidence that this may not be the case for all of these diverse hyperthermophilic species.

Invasive Species

Lake trout are an example of an invasive species of fish that is decimating the native cutthroat trout population in Yellowstone Lake.

Tourist information

Yellowstone is one of the most popular national parks in the United States. The park is unique in that it features multiple natural wonders all in the same park. At peak summer levels, 3,500 employees work for Yellowstone National Park concessioners and about 800 work for the park.

Geysers, hot springs, a grand canyon, forests, wilderness, wildlife and even a large lake can all be found inside the park. Due to the park's diversity of features, the list of activities for visitors is nearly endless. From backpacking to mountaineering, from kayaking to fishing, from sightseeing to watching bison, moose, and elk wandering into the parking lot of the visitor centers, most visitors enjoy a memorable experience in nature.

Most of the geothermal features (hot springs, geysers, etc) emit gaseous sulfur, and though to most people the odor is not terribly offensive or overwhelming, people with respiratory difficulties should consult their doctors before visiting.

Wildfires are a relatively common occurrence in Yellowstone, because of the dry summer climate, but they should not be considered "disasters"; instead, they are a regular natural process that contributes to the beauty and ecology of the park. A series of wildfires in 1988 burned about 45% of the park's forest, including some forests adjacent to the major tourist areas. The areas burned in the 1988 fire present a strange, stark beauty, and the burned areas are swiftly returning to green.

Park officials advise visitors not to approach dangerous animals and to stay on designated safe trails to avoid falling into boiling liquids and inhaling toxic gas. In 2004, five bison were discovered dead from an apparent inhalation of toxic geothermal gases.

Lodging for visitors exist at 11 locations within park boundaries. There is a clear view of Old Faithful Geyser at the park's Old Faithful Inn. Lodges range from hotel to cabin accommodations. There also are 11 campgrounds and one hard-sided recreational vehicle park.

The park itself is surrounded by other protected lands (including Grand Teton National Park and Custer National Forest) and beautiful drives (such as the Beartooth Highway). Nearby communities include West Yellowstone, Montana; Cody, Wyoming; Red Lodge, Montana; Ashton, Idaho; and Gardiner, Montana.

References

• Geology of National Parks: Fifth Edition, Ann G. Harris, Esther Tuttle, Sherwood D. Tuttle (Iowa, Kendall/Hunt Publishing; 1997) ISBN
• Playing God in Yellowstone, Alston Chase (1986) ISBN
• National Park Service
• Yellowstone Park Foundation
• Vazquez, J.A., and Reid, M.R., 2002, Time scales of magma storage and differentiation of voluminous rhyolites at Yellowstone caldera, Wyoming: Contributions to Mineralogy & Petrology, v. 144, p. 274-285
• Yellowstone National Park Census Divisions United States Census Bureau

See Also

• National Park Service

External links

• Yellowstone National Park Official site
• An extensive Yellowstone photograhic galary on the official NPS.gov site Images should be free under public licence for Wiki-pedia use.
• An Interactive Yellowstone Map Includes Points of Interest
• Climate data for Yellowstone National Park
• Yellowstone page on Stromboli online
• Yellowstone National Park Wildland Fire Images - Fires of 1988 public domain images.
• USGS: Volcanic History of the Yellowstone Plateau Volcanic Field
• Buffalo Field Campaign, working to stop the slaughter of Yellowstone's wild free roaming buffalo
• h2g2 has articles about the origin of Yellowstone, its geology , its *early history and European exploration.
• Life at high temperatures - An introduction to Yellowstone's thermophilic bacteria.
• Primal Nature Essay: Impact of the Reintroduction of Wolves in Yellowstone
• Scientific American Magazine (June 2004 Issue) Lessons from the Wolf

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