Yellowstone National Park is located in the United States of America and more precisely in the extreme north-western sector of the state of Wyoming and borders, for a small stretch, into the states of Montana (to the north) and ‘Idaho (to the west), occupying a large area of the Rocky Mountains.
The name Yellowstone (yellow stone) derives from active volcanic phenomena and the yellow stone probably derives from the sulfur present in the area; it is the core of the Greater Yellowstone Ecosystem, one of the largest intact temperate zone ecosystems left on Earth. It is the oldest national park in the world (founded in 1872 during the presidency of Ulysses S. Grant) and the largest protected area in the United States; in 1978 it was declared a World Heritage Site by UNESCO. In 2015, the park was visited by more than 4,000,000 people.
Geology: Geysers and rock formations
The park is famous for its numerous geysers (over 300), 10 000 hot springs (200 ° C) and other interesting even if less conspicuous geothermal areas. All these activities are a remnant of the intense volcanic activity and related upheavals that led to the formation of the central Rocky Mountain barrier.
Earthquakes are frequent in the Park, almost one is recorded a year. In the history of Yellowstone there are as many as 6 that reached magnitude 6, including one of 7.5 that hit an area just outside the park’s northwest boundary in 1959. This triggered a huge landslide that caused the partial destruction of the dam on Lake Hebgen. The rock sediments that came with the landslide in the valley dammed the river so as to form a new lake, Lake Earthquake (Lake of the Earthquake). On this occasion there was also the birth of some geysers in the north-western section of the park.
The park is very important nationally and internationally for being populated by rare and often endangered species. There are nearly 60 mammal species in the park, including:
In 1902 in Yellowstone, there were fewer than 35 specimens of bison in 2003 it reached the enormous figure of 4,000 specimens. The Plains bison population peak was reached in 2005 with 4,950 head. The population then slowly decreased until reaching 2,500 specimens in 2008. The causes of the decline in the population were many, including the cold winter of 2007 which killed many animals.
Northwestern Gray Wolf
The wolves were thus hunted all over the USA, and by 1926 they had been completely exterminated in Yellowstone. Without the wolves, the coyote became the park’s main canine predator. However, the coyote cannot kill large animals, such as bison and wapiti. The result was an increase in the number of lame and diseased herbivores.
In 1990, the Federal Government revised its view on wolves. In a controversial decision by the US Fish And Wildlife Service, the first 14 wolves, imported from Canada, were finally reintroduced to the park in 1995. This is the only project ever carried out in the world to reintroduce the wolf in the wild.
The project was a great success, leading researchers to discover the influence of the predator on species and habitats, defining the trophic cascades of the wolf. The Yellowstone researchers claimed that the predator, by controlling the ungulate population, had modified the rivers, favoring an uplift in the health of waterways and their morphology and an enrichment of biodiversity in general.
More than 700 grizzly bears live in the Greater Yellowstone ecosystem, more than half of them within Yellowstone.
The population of wapiti had reached the enormous figure of 30,000 specimens, creating considerable problems for the vegetation of the Park. Since the mid-1990s, after the reintroduction of wolves, the herd has significantly decreased; however, it enjoys excellent health because old or sick individuals are eliminated. Each fall, more than 7,500 wapiti migrate south through Grand Teton National Park to spend the cold season on the plains of the National Elk Refuge.