Yellowstone, as a whole, possesses close to 60 percent of the world's geysers. The Upper Geyser Basin is home to the largest numbers of this fragile feature found in the park. Within one square mile there are at least 150 of these hydrothermal wonders. Of this remarkable number, only five major geysers are predicted regularly by the naturalist staff. They are Castle, Grand, Daisy, Riverside, and Old Faithful.
There are many frequent, smaller geysers to be seen and marveled at in this basin as well as numerous hot springs and one recently developed mudpot (if it lasts).
Biscuit Basin is one of three basins that make up the Upper Geyser Basin.
The name Biscuit Basin was adopted in the late 1880s because of the unusual biscuit-shaped geyserite formations that used to surround Sapphire Pool. Following the 1959 Hebgen Lake earthquake, Sapphire erupted—and the “biscuits” were blown away.
Castle Geyser has the largest cone and may be the oldest of all geysers in the basin. Its eruption pattern has changed considerably throughout its recorded history. Castle is currently erupting about every 10 - 12 hours. A water eruption frequently reaches 90 feet (27m) and lasts about 20 minutes. The water phase is followed by a noisy steam phase lasting 30 - 40 minutes.
This large area of hydrothermal activity can be viewed by foot along the boardwalk trail at Fountain Paint Pots and by car along the three mile Firehole Lake Drive. The latter is a one-way drive where you will find the sixth geyser predicted by the Old Faithful staff: Great Fountain. Its splashy eruptions send jets of diamond droplets bursting 100-200 feet in the air, while waves of water cascade down the raised terraces. Patience is a virtue with this twice-a-day geyser, as the predictions allow a 2 hour +/- window of opportunity.
Fountain Flats Drive departs the Grand Loop Road just south of the Nez Perce picnic area and follows along the Firehole River to a trailhead 1.5 miles distant.
From there, the Fountain Freight Road hiking/biking trail continues along the old roadbed giving hikers access to the Sentinel Meadows Trail and the Fairy Falls Trail. Also along this path is the only handicapped-accessible backcountry site in the Old Faithful district at Goose Lake.
This geyser basin, though small in size compared to its companions along the Firehole River, holds large wonders for the visitor. Excelsior Geyser reveals a gaping crater 200 x 300 feet with a constant discharge of more than 4,000 gallons of water per minute into the Firehole River. Also in this surprising basin is Yellowstone's largest hot springs, Grand Prismatic Spring. This feature is 370 feet in diameter and more than 121 feet in depth.
This backcountry geyser basin is easily reached by a 5-mile roundtrip hike from the trailhead south of Old Faithful. Lone Star Geyser erupts about every three hours. There is a logbook, located in a cache near the geyser, for observations of geyser times and types of eruptions.
Shoshone Geyser Basin is reached by a 17-mile roundtrip hike that crosses the Continental Divide at Grant's Pass. This basin has no boardwalks, and extreme caution should be exercised when travelling through it. Trails in the basin must be used. Remote thermal areas, such as this, should be approached with respect, knowledge, and care. Be sure to emphasize personal safety and resource protection when entering a backcountry basin.
The river derives its name from the steam (which they thought was smoke from fires) witnessed by early trappers to the area. Their term for a mountain valley was "hole," and the designation was born. The Firehole River boasts a world-famous reputation for challenging fly-fishing. Brown, rainbow, and brook trout give the angler a wary target in this stream.
Craig Pass/Isa Lake
Both names are used to describe the same location seven miles south of Old Faithful on the Grand Loop Road. At 8,262 feet along the Continental Divide, Isa Lake is a uniquely confusing feature. During spring runoff, it drains into both the Atlantic and Pacific Oceans at the same time! (And backwards, too!) The west side of the lake flows into the Firehole drainage and, eventually, the Atlantic throughout the year. The east side, during spring, flows toward the Snake River drainage and the Pacific.
Kepler Cascades is the most easily reached waterfall in the district. A marked pullout just south of Old Faithful and a short walk from the car offers the visitor easy access to view this 125-foot cascade.
Mystic Falls and Fairy Falls: (see Day Hiking Trails section for information on these features).