With half of the earth’s geothermal features, Yellowstone holds the planet’s most diverse and intact collection of geysers, hot springs, mudpots, and fumaroles. Its more than 300 geysers make up two thirds of all those found on earth. Combine this with more than 10,000 thermal features comprised of brilliantly colored hot springs, bubbling mudpots, and steaming fumaroles, and you have a place like no other.
Yellowstone’s hydrothermal features would not exist without the underlying magma body that releases tremendous heat. They also depend on sources of water, such as from the mountains surrounding the Yellowstone Plateau. There, snow and rain slowly percolate through layers of permeable rock riddled with cracks. Some of this cold water meets hot brine directly heated by the shallow magma body. The water’s temperature rises well above the boiling point but the water remains in a liquid state due to the great pressure and weight of the overlying water. The result is superheated water with temperatures exceeding 400 ° F.
The superheated water is less dense than the colder, heavier water sinking around it. This creates convection currents that allow the lighter, more buoyant, superheated water to begin its journey back to the surface following the cracks and weak areas through rhyolitic lava flows. This upward path is the natural “plumbing” system of the park’s hydrothermal features. Once it reaches the surface, the various colors of the pools are due to different types of bacteria growing in different temperatures.
Flora and fauna
The park is the core of the Greater Yellowstone Ecosystem, one of the largest intact temperate zone ecosystems remaining on the planet, and as a result is an exceptional area for wildlife viewing.
Yellowstone is home to the largest concentration of mammals in the lower 48 states. Sixty-seven different mammals live here, including grizzly bears and black bears. Gray wolves were restored in 1995 and more than 100 live in the park now. Wolverine and lynx, which require large expanses of undisturbed habitat, are also found in the Yellowstone ecosystem. Seven native ungulate species – elk, mule deer, bison, moose, bighorn sheep, pronghorn, and white – tailed deer live here. Non-native mountain goats have colonized northern portions of the park and numerous small mammals are found throughout the park.
Records of bird sightings have been kept in Yellowstone since its establishment in 1872; these records document 330 species of birds to date, of which approximately 148 species are known to nest in the park. The variation in elevation and broad array of habitat types found within the park contributes to the region’s relatively high diversity.
Glacial activity and current cool and dry conditions are likely responsible for the relatively small number of reptiles and amphibians found in the park.
Yellowstone is home to more than 1,350 species of vascular plants, of which 218 are non-native.
The weather in Yellowstone National Park can change very rapidly from sunny and warm to cold and rainy, so it’s important to bring along extra layers of clothing which can be used as needed.
- Summer: Daytime temperatures are often in the 70s (25°C) and occasionally in the 80s (30°C) in lower elevations. Nights are usually cool and temperatures may drop below freezing at higher elevations. Thunderstorms are common in the afternoons.
- Winter: Temperatures often range from zero to 20°F(-20°C to -5°C) throughout the day. Sub-zero temperatures over-night are common. The record low temperature is -66F (-54°C). Snowfall is highly variable. While the average is 150 inches per year, it is not uncommon for higher elevations to get twice that amount.
- Spring & Fall: Daytime temperatures range from the 30s to the 60s (0 to 20°C) with overnight lows in the teens to single digits (-5 to -20°C). Snow is common in the Spring and Fall with regular accumulations of 12″ in a 24 hour period. At any time of year, be prepared for sudden changes. Unpredictability, more than anything else, characterizes Yellowstone’s weather. Always be equipped with a wide range of clothing options. Be sure to bring a warm jacket and rain gear even in the summer.