The park was first viewed by people from the United States relatively late. The Rocky Mountain ranges which surround the park area， and its remotenessremoteness n.远离， 遥远， are largely responsible for this. The first white man to visit the Yellowstone area was probably the famous mountain man and adventurer John Colter， who wandered throughout the Rocky Mountain area in 1807~1808 following completion of his participation in the Lewis and Clark expedition.
Although the area was frequented by trappers， it was largely unmapped until after the Civil War. The Hayden Geological and Geographical Survey in 1871 piqued public interest in the many unusual features that existed in the area. Additional notorietynotoriety n.恶名， 丑名， 声名狼藉， 远扬的名声 was gained through the work of painter Thomas Moran and photographer William H.Jackson. The idea for a national park was promoted by Cornelius Hedges， Nathanial Longford， and others. With support from the Northern Pacific Railroad， which saw the potential benefits on tourism， the bill creating the park was signed by President Ulysses S. Grant on March 1， 1872.
Hydrothermal Features
Without question Yellowstone，s most famous items are the hydrothermalhydrothermal adj.热水的， 热液的 features found throughout the park. These features are the result of the “Yellowstone Hot Spot” - a section where the thickness of the earth，s crust is extremely thin. The magma below the crust is less than two miles thick in this area； the planet，s internal heat is closer to the surface here than anywhere else on earth. Water from heavy precipitation in the area seeps down through the ground until it it is superheated， begins to rise， and eventually returns to the earth as a geyser， hot spring， pool， mud pot， or other hydrothermal feature. This trip from surface to surface may take 500 years.
The most famous of the hydrothermal features is Old Faithful， whose eruptions have been witnessed by millions. Although there is a popular misconceptionmisconception n.误解 that the geyser erupts once per hour， in reality it averages an eruption every hour and a half or so. It was named for its regularity by members of the WashburnLongford Expedition in 1870.
The hydrothermal features are varied. Below， on the left， is Abyss Pool in the West Thumb Geyser Basin. This is the deepest pool in the park， hence its name， and actually erupted as a geyser in 1987. On the right is the “cooking hillside” near Mud Volcano. This barrenbarren adj.不生育的， 不孕的， 贫瘠的， 没有结果的， 无益的， 单调的， 无聊的， 空洞的 n.荒地 area， once covered with trees and other vegetation， changed as a result of a number of earthquakes in 1978~1979 which radically increased soil temperatures to around 200 degrees Fahrenheit.
One of the most interesting locations which contains hydrothermal features is the Mammoth Hot Springs area in the far north portion of the park. Here water containing calcium and bicarbonate rises to the surface where carbon dioxide escapes and the remaining carbonate is combined with calcium to form travertine， which is deposited on the surface in fantasticfantastic adj.幻想的， 奇异的， 稀奇古怪的， 荒谬的， 空想的 shapes and formations.
Wildlife
Yellowstone，s wildlife is as spectacular as the hydrothermal features. Because of the park，s remote location， and because of its large size， animals roam freely and are able to live in a natural way much as their kind have lived for centuries. Large animals in the park are not hunted， herded， or fed. Because there are many areas within the park with panoramicpanoramic adj.全景的 views or where meadows break up forested areas it is relatively easy to see the wildlife in its natural state. Many kinds of animals have little fear of people and can be approached fairly closely.
The animal which comes first to mind when Yellowstone is mentioned is probably the buffalo， the largest land mammal in North America. These animals， such as the one below peacefully munching grass， can be seen all over the park， in herds with many other animals or alone.
Moose can also be seen along waterways and in clearings. These large animals may weigh up to 1400 pounds， stand 7.5 feet at the shoulder， and have antlers which may spread up to 5 feet. They feed on willows and aquatic vegetationaquatic vegetation 水生植物群(落) such as water lilies. The bull below was sighted in the northern section of the park.
Wapiti， or elk， are also numerous； about 38，000 of these animals currently roam the park， as their progenitors have done for 12，000 years. Male elk typically weigh 600~1100 pounds and stand 5 feet at the shoulders. Females weight from 450~600 pounds. The female below is browsing on seedlings which form part of the normal elk diet.
Rivers， Waterfalls， Lakes
There are lots of creeks and rivers in the park. On the left below is the Firehole River as it flows towards the Upper Geyser Basin. Because of the abundant runoff from the geothermal features in this area the river is very warm year round. Never freezing during the winter， it is a popular gathering place for wildlife during that season when the park is dominated by freezing temperatures and deep snow. On the right is Lewis Falls， 37 feet high， on the Lewis River in the south central portion of Yellowstone.
Cascades and waterfalls are abundant as well. On the left below is Kepler Cascades on the Firehole River not far from the upper Geyser Basin， and on the right is Gibbon Falls on the Gibbon River midway between Madison and Norris.
In the central portion of the park is Yellowstone Lake， the largest lake in the world over 7，000 feet (its exact altitude is 7，733 feet). The coast of this lake is over 100 miles in length.The view below looks southwest across the lake toward the Absaroka Mountains in the background.
Although the lake was once twice its present size， it still averages 137 feet in depth with a maximum depth of 320 feet. It is so large that it takes 11 years for all of the water in the lake to be completely recycledrecycle v.使再循环， 反复应用 n.再循环， 再生， 重复利用！ A view looking east across the lake is shown below on the left， while the right picture shows a portion of the coast of West Thumb Bay.