Yellowstone National Park

Yellowstone: America’s First National Park and the Caldera Underneath It

In July and August, the parking lot at Grand Prismatic Spring in the Midway Geyser Basin fills before 8am. Old Faithful’s boardwalk benches fill 30 minutes before each predicted eruption. Yellowstone receives 4 million visitors per year and they concentrate in two months and two dozen locations. The practical strategy is either to plan for May or September, shoulder season, quieter roads, accommodation available, or to wake up significantly earlier than feels reasonable on vacation. The park at 6am is a different country than the park at 11am.

Yellowstone became the world’s first national park in 1872, when President Grant signed the legislation setting it aside. It sits on top of a volcanic hotspot with more geothermal features than anywhere else on earth. The people who pushed for that designation understood they were preserving something geologically singular: a volcanic hotspot that powers more geothermal features than anywhere else on earth. What they may not have fully appreciated is that Yellowstone sits on top of a supervolcano caldera about 72 by 55 kilometres in dimension. The caldera last erupted around 640,000 years ago. The ground in some sections is noticeably warm.

The Geysers

Old Faithful erupts roughly every 90 minutes, though the interval varies between 60 and 110 minutes depending on the duration of the previous eruption. The rangers post a predicted eruption time (accurate within 10 minutes) on boards near the visitor centre. The eruption lasts 1.5 to 5 minutes and reaches heights between 30 and 55 metres. It is genuinely impressive but also genuinely routine by Yellowstone standards; the park has over 500 geysers, more than half of all geysers on earth.

Norris Geyser Basin, about 30 kilometres north of Old Faithful, has the hottest and most acidic thermal area in the park and a different character: small vents, steaming ground, and pools in acidic blues and yellows rather than the Grand Prismatic’s vivid colours. Steamboat Geyser, at Norris, is the world’s tallest currently active geyser (heights up to 91 metres) but erupts unpredictably; waiting for it is not a practical strategy.

Grand Prismatic Spring in the Midway Geyser Basin is the largest hot spring in the United States (112 metres diameter) and has the most vivid colour spectrum, going from deep blue at the centre through green, yellow, and orange rings to rust at the edges. The colours come from heat-loving microorganisms, each colour zone inhabited by a different species at a different temperature tolerance. The view from the boardwalk is good but partial; the aerial view (from a hill behind the basin, about a 15-minute scramble up a social trail on the south side) gives the full picture.

Lamar Valley and Wildlife

Lamar Valley in the park’s northeast corner is the best place in the continental US to see wolves. The Yellowstone Wolf Project reintroduced wolves from Canada in 1995-96 after a 70-year absence; the population has stabilised around 100 animals in approximately 10 packs. Wolf watching in Lamar requires early morning (6am or before), patience, binoculars or a spotting scope, and ideally a wolf observation guide (the nonprofit Yellowstone Forever runs wolf-watching programs that significantly improve sighting odds).

Bison are the park’s most reliable large mammal. Over 5,000 live in Yellowstone and they are everywhere: on the road, in the valley, occasionally leaning against parked cars. They look placid and are not; they injure more visitors per year than any other animal in the park. The rule is to stay 25 yards away at minimum and more if the animal is showing any tension. Running bison reach 35 miles per hour; humans do not.

Grizzly bears are present (around 700 in the Greater Yellowstone Ecosystem) but not reliably visible. The road between Norris and Canyon has produced morning sightings consistently. Carry bear spray, know how to use it, and make noise on trails.

Practical Planning

The park receives 4 million visitors per year and the concentration in July and August is severe: Yellowstone’s internal roads are two-lane and often congested, Old Faithful’s parking lot fills by 8am, and the Grand Prismatic boardwalk is standing-room only from 10am to 4pm. Plan for a mid-May or September-October visit if possible.

Entrances: there are five. West Entrance at West Yellowstone, Montana, handles the most traffic. South Entrance connects to Grand Teton National Park. North Entrance at Gardiner, Montana, is the only year-round entrance open to wheeled vehicles.

The Grand Loop Road (225 miles round trip, or 142 miles for the shorter figure-eight loop) connects most major features and has a series of well-placed turnouts. Allow at least 3 days to see the highlights without rushing; 5 days is better.

Inside-the-park accommodation (Old Faithful Inn, Canyon Lodge, Lake Hotel) books out by January for summer visits. Reserve through the park’s concessioner, Xanterra, as early as possible. Outside options in West Yellowstone and Gardiner fill fast too, but are generally available with 4-6 weeks’ notice.

Food inside the park is functional and expensive; pack what you can. The restaurants at Old Faithful Inn and Lake Hotel are the best options and worth a meal at one of them for the dining room atmospheres.