Yellowstone Park
Yellowstone is one of the most famous national parks in the world. It became the very first national park on Earth in 1872. Yellowstone is famous for its geysers (including the predictable Old Faithful), its herds of bison and elk, its grey wolves, and the giant supervolcano that lies beneath it.
- CountryUnited StatesMostly in Wyoming, plus parts of Montana and Idaho
- Area8,983 km²Bigger than Cyprus
- Founded1872First national park in the world
- GeysersOver 500About half of all the geysers on Earth
- Most famous geyserOld FaithfulErupts roughly every 90 minutes
- Visitorsapprox. 4 million/yearOne of the most-visited US national parks
How big is Yellowstone compared to other US parks?
Yellowstone is roughly twice the size of the Grand Canyon National Park, and 2,600 times the size of Central Park in New York.
What is Yellowstone?
Yellowstone is a huge wilderness mostly in the US state of Wyoming, with smaller parts stretching into Montana and Idaho. It covers around 9,000 square km of mountains, forests, rivers, lakes and meadows. The park is famous for its volcanic and geothermal features (geysers, hot springs, mud pots) and its abundant wildlife, all kept safe by the fact that the area has been protected for over 150 years.
Geysers and hot springs
Yellowstone sits on top of a giant pool of molten rock approx. 8 km underground. Surface water trickles down through cracks in the rock, gets superheated by this magma, and then either explodes back to the surface as a geyser or bubbles out gently as a hot spring. Yellowstone has over 500 geysers, about half of all the geysers in the world, plus thousands of hot springs and mud pots.
The most famous geyser is Old Faithful, which erupts on a predictable schedule of roughly every 60 to 110 minutes, sending up to 32,000 litres of boiling water 40 to 55 metres into the air. The most spectacular hot spring is Grand Prismatic Spring, a giant rainbow-coloured pool whose colours are caused by different kinds of heat-loving bacteria living in the different temperature zones.
Wildlife of Yellowstone
Yellowstone has the most varied and abundant wildlife in the lower 48 American states. It is home to around 4,000 American bison, the only place in the US where they have lived continuously since prehistoric times. It also has elk, moose, mule deer, pronghorn antelope, bighorn sheep, mountain goats, black bears, grizzly bears, coyotes, cougars, and (since 1995) a returning population of grey wolves.
The return of the wolves
Wolves were hunted to extinction in Yellowstone by the 1920s, when they were considered dangerous pests. In 1995 and 1996, biologists carefully reintroduced 41 wolves from Canada into the park. The results have been astonishing.
The wolves controlled the elk population, which had grown too big and was eating all the young willow and aspen trees along the rivers. With fewer elk, the willows grew back, providing habitat for songbirds and beavers. Beavers built dams that created new wetlands. The whole river ecosystem changed. Wolves have also helped songbirds, fish and even insects come back. The wolf reintroduction is one of the great success stories of modern ecology and is now studied around the world.
Deeper dive: the Yellowstone supervolcano, the national park idea, and trophic cascades
The Yellowstone Caldera is one of the largest volcanic features on Earth. It is fed by a giant magma chamber that sits between 5 and 17 km beneath the surface and contains around 25,000 cubic km of partially molten rock. Three colossal eruptions have happened here in the last 2.1 million years (2.1 million years ago, 1.3 million years ago and 640,000 years ago). The most recent of these three was around 1,000 times larger than the 1980 Mount St Helens eruption and threw enough ash to cover much of the western United States. Yellowstone has had many smaller eruptions in between, the most recent only 70,000 years ago. The volcano is constantly monitored by the United States Geological Survey, which assesses the current risk of a supereruption as "extremely low" on any human timescale.
The idea of a "national park" (a wilderness area set aside not for hunting or farming but for everyone to enjoy in its natural state) was essentially invented when President Ulysses S. Grant signed the act creating Yellowstone in 1872. The concept then spread around the world: Australia's Royal National Park (1879), Canada's Banff (1885), New Zealand's Tongariro (1887), South Africa's Kruger (1898) and many others. Today over 200 countries have some form of national park system, protecting roughly 16% of the world's land area.
The wolf reintroduction has become a famous example of a trophic cascade: a change at the top of a food chain that ripples down through many lower levels. Removing top predators (in this case wolves) caused an explosion of large herbivores (elk), which damaged plants, which damaged the animals depending on those plants, which damaged the soil and rivers. Adding the wolves back reversed the cascade. Trophic cascades are now thought to be a major factor in the health of many ecosystems, and have influenced conservation strategies from African savannas to coral reefs.
The country is the United States. Another famous American landmark is the Statue of Liberty.