Yellowstone: A Supervolcano, Geysers and Wildlife in the World’s First National Park

The Grand Geyser, the largest predictable geyser in Yellowstone, can spout boiling water over 150 feet (46 m) in the air (photo: David L. Sifry, CC BY-SA 3.0).

Yellowstone sits on the caldera of a supervolcano whose last eruption was about 640,000 years ago, and it holds more than 300 geysers and more than 10,000 thermal features. Set aside in 1872, it was the world’s first national park and is a UNESCO World Heritage Site. It covers 3,472 square miles, mostly in the northwest corner of Wyoming, with portions in Idaho and Montana. This overview leaves out the Wikivoyage guide’s fees, phone numbers, hours and lodging and food listings.

A park on a supervolcano

On March 1, 1872, President Ulysses S. Grant declared Yellowstone the first national park reserve anywhere in the world, and in 1978 it became a World Heritage Site. The park is often assumed to be named for the yellow rocks of the Grand Canyon of the Yellowstone, but its name comes from the Yellowstone River, which is named for sandstone bluffs farther down its course in eastern Montana.

Long before recorded history, a massive eruption covered the western U.S., much of the Midwest, parts of the East Coast, northern Mexico and some areas of Canada in ash, and left a caldera about 34 by 45 miles (55 by 72 km). The guide classes Yellowstone as a supervolcano whose last eruption is thought to have been a VEI-8 event, and says such eruptions are believed to come every 600,000 to 900,000 years.

The hydrothermal features exist because of the magma body beneath, which releases tremendous heat, and water from the mountains around the Yellowstone Plateau. Snow and rain seep through cracked rock until some meets hot brine heated by the shallow magma. The water rises well above the boiling point but stays liquid under the weight of the water above, reaching above 400 °F (200 °C), and climbs back to the surface along cracks and weak areas in rhyolitic lava flows, the natural plumbing of the geysers, hot springs, mudpots and fumaroles. Different bacteria growing at different temperatures give the pools their colors.

Geysers and hot springs, area by area

The guide divides the park into about eight areas, described in a clockwise tour starting from the east.

Old Faithful. The geyser most people picture when they think of Yellowstone erupts regularly, on average about once every eighty minutes, though the interval varies by as much as an hour and has been getting longer; rangers can predict an eruption to within about ten minutes if they know how long the previous one lasted. The Upper Geyser Basin has an additional 150 geysers in a single square mile, and the naturalists regularly predict the eruptions of Castle, Grand, Daisy and Riverside as well as Old Faithful; Great Fountain, in the Lower Geyser Basin, is the sixth they predict. The Midway Geyser Basin holds Yellowstone’s largest hot spring, Grand Prismatic Spring, 370 feet (110 m) across and 160 feet (50 m) deep, and a platform on the hill behind it, reached from the Fairy Falls trailhead, gives an elevated view. Old Faithful Inn, built in the winter of 1903-04, is one of the few remaining log hotels in the United States.

Grand Prismatic Spring seen from above, with raised boardwalks around the spring and nearby pools (photo: David L. Sifry, CC BY-SA 3.0).

Norris. Norris Geyser Basin is the hottest, oldest and most dynamic of the park’s thermal areas, and its features change daily. The highest temperature yet recorded in any Yellowstone geothermal area, 459 °F (237 °C), was measured in a scientific drill hole there just 1,087 feet (331 m) below the surface. Steamboat Geyser, the tallest geyser in the world at 300 to 400 feet (90 to 120 m), is in this area.

Mammoth. Mammoth is home to the park headquarters and the calcite terraces of Mammoth Hot Springs, reached by boardwalk. Travertine formations grow much faster than the sinter formations elsewhere because limestone is softer: hot water rising through limestone dissolves large quantities of rock and deposits a white chalky mineral at the surface. Formations change rapidly, and a spring that seems to have died may simply be one of the “on-again-off-again” ones.

West Thumb. On the western side of Yellowstone Lake, the area is named because the lake, with a little imagination, looks like a left hand reaching south and this is its thumb. Fishing Cone, a hot spring that bubbles out directly into the lake, was once used to cook newly caught fish; that stunt is no longer allowed.

Canyon, lake and wildlife

The Grand Canyon of the Yellowstone is roughly 20 miles (32 km) long and 800 to 1,200 feet (240 to 370 m) deep, and the present canyon is no more than 10,000 to 14,000 years old, though there has probably been a canyon here far longer. Chemical processes have left stripes and patches of color in its rock. The Upper Falls drop 109 feet (33 m) and the Lower Falls 308 feet (94 m); Tower Fall is 132 feet (40 m).

The Grand Canyon of the Yellowstone and Yellowstone Falls (photo: Brocken Inaglory, CC BY-SA 3.0).

Yellowstone Lake covers 132 square miles (340 square kilometres) at 7,733 feet (2,357 m) above sea level, the largest lake at high elevation in North America, and it is frozen nearly half the year. Swimming is not recommended in its cold water, and boaters have died when calm weather turned into violent storm within minutes.

The park is the core of the Greater Yellowstone Ecosystem, one of the largest intact temperate zone ecosystems remaining on the planet, and has the largest concentration of mammals in the lower 48 states: sixty-seven species, including grizzly bears and black bears. Gray wolves were hunted to extinction by 1926 and reintroduced from Canada in 1995, and the guide says more than 100 live in the park. Seven native ungulate species live here: elk, mule deer, bison, moose, bighorn sheep, pronghorn and white-tailed deer. Records show 330 bird species, about 148 of which nest in the park. Hayden Valley is one of the best places to see wildlife, with grizzly bears in spring and early summer and large bison herds in spring, early summer and the fall rut; the Lamar Valley, east of Tower, has one of the more accessible wolf packs.

Bears such as this black bear are often seen near the roadways or on the ridges in summer, usually foraging for food (photo: Brocken Inaglory, CC BY-SA 3.0).

Getting around, and the weather

The park’s roads form a figure 8: the lower loop is about 90 miles (140 km) around and the upper loop about 70 miles (110 km). There are five entrances, and only the north (from Gardiner) and northeast (from Silver Gate and Cooke City) stay open all year. No public transportation runs inside the park, so most visitors drive, and roads clog whenever people stop to look at wildlife. In winter, travel is by commercial snowcoach or with a commercial guide on a snowmobile.

The weather can change from sunny and warm to cold and rainy in no time, and snow can fall in any month. Summer days are often in the 70s °F (25 °C) with cool nights; winter days range from zero to 20 °F (-20 to -5 °C), and the record low is −66 °F (−54 °C). Visitors should carry extra layers at any time of year.

Staying safe

Park authorities say to stay at least 100 yards or meters from bears and wolves and 25 from all other wild animals, because bison, elk, moose, bears and nearly all large animals can attack, and dozens of visitors are injured each year by getting too close. Odors attract bears, so food, garbage and toiletries must be secured. It is illegal to swim or bathe in thermal pools, and visitors must stay on the boardwalks: scalding water lies under thin, breakable crusts, people who leave the trails are seriously burned every year, and some have died. Mobile phones do not work in most of the park, weather can turn quickly, lightning has injured and killed people, and even clear water may be polluted and should be purified.

Sources

• Wikivoyage, Yellowstone National Park, by its contributors, licensed under CC BY-SA 4.0; photos by David L. Sifry and Brocken Inaglory, each CC BY-SA 3.0. Changed here: condensed and rewritten as an overview, with the fees, phone numbers, opening hours and lodging, food and service listings left out; rewritten in hubnx's own words.