Old Faithful: Yellowstone's Iconic Geyser

Old Faithful is a cone geyser in Yellowstone National Park, Wyoming, famous for its highly predictable eruptions. It shoots 14,000 to 32,000 liters of boiling water 32 to 56 meters (106 to 185 feet) into the air every 44 to 125 minutes, with an average interval of approximately 92 minutes. Since its discovery by the Washburn-Langford-Doane Expedition in 1870, it has erupted over 1 million times.

Introduction

Located at coordinates 44.4605°N, 110.8281°W in the Upper Geyser Basin of Yellowstone, Old Faithful sits at an elevation of 2,240 meters (7,349 feet) above sea level. It is part of the world's largest concentration of geysers — Yellowstone contains over 500 of the roughly 1,000 geysers on Earth, all powered by the Yellowstone Supervolcano's massive magma chamber lying just 5 to 15 kilometers beneath the surface.

Geography & Location

• Coordinates: 44.4605°N, 110.8281°W
• Elevation: 2,240 m (7,349 ft)
• Basin: Upper Geyser Basin
• Park: Yellowstone National Park, Wyoming

Old Faithful is located in the Upper Geyser Basin, which contains the highest concentration of geysers in the world — approximately 150 within a 2.6-square-kilometer area. The basin sits along the Firehole River in the west-central portion of Yellowstone. Nearby geysers include Grand Geyser (the world's tallest predictable geyser at 61 meters), Castle Geyser, and Beehive Geyser.

Yellowstone National Park spans 8,983 square kilometers across Wyoming, Montana, and Idaho, centered on the Yellowstone Caldera — the remnant of a supervolcanic eruption that occurred 640,000 years ago. The caldera measures 72 by 55 kilometers and is one of the largest active volcanic systems on Earth. The geothermal energy powering Old Faithful and all of Yellowstone's hydrothermal features comes from this magma chamber.

Eruption Characteristics

• Average Interval: ~92 minutes
• Duration: 1.5–5 minutes
• Water Temperature: 95.6°C (204°F) at the vent
• Volume per Eruption: 14,000–32,000 liters

Old Faithful's eruption interval ranges from 44 to 125 minutes, with the duration of the previous eruption serving as the best predictor of the next. A short eruption (about 2 minutes) typically leads to a shorter interval (~65 minutes), while a long eruption (4–5 minutes) predicts a longer interval (~92 minutes). Park rangers predict eruptions within a 10-minute window with approximately 90 percent accuracy.

The geyser works through a simple but powerful mechanism: groundwater seeps into a deep, constricted underground plumbing system where it is superheated by magma-warmed rock to temperatures above the normal boiling point. The constriction prevents the water from boiling until pressure builds to a critical point, then the entire water column erupts explosively. After the eruption, the system refills and the cycle begins again.

Geology & the Yellowstone Supervolcano

• Magma Depth: 5–15 km below surface
• Last Major Eruption: 640,000 years ago
• Caldera Size: 72 x 55 km
• Geysers in Yellowstone: 500+ (half the world's total)

The Yellowstone Supervolcano has produced three caldera-forming eruptions in the past 2.1 million years: 2.1 million, 1.3 million, and 640,000 years ago. The most recent eruption ejected approximately 1,000 cubic kilometers of material — 2,500 times more than the 1980 Mount St. Helens eruption. The magma chamber still generates enough heat to power the park's 10,000+ thermal features.

Yellowstone's hydrothermal system is the most diverse and active on Earth, including geysers, hot springs, mudpots, and fumaroles. The system circulates approximately 300 liters of heated water per second. Old Faithful's plumbing extends at least 22 meters deep, with the underground chamber holding roughly 8,000 liters of water that recharges between eruptions.

Visitor Information

• Annual Visitors: ~4.9 million (Yellowstone total)
• Viewing Area: Amphitheater-style boardwalk seating
• Old Faithful Inn: Historic 1904 log hotel, 327 rooms
• Prediction Updates: Posted in visitor center and NPS app

Old Faithful is the centerpiece of Yellowstone's most developed visitor area. An amphitheater-style boardwalk provides seating for hundreds of visitors around the geyser cone, and predictions of the next eruption are posted in the Old Faithful Visitor Education Center, at nearby lodges, and on the Yellowstone National Park app. Approximately 4.9 million people visit the park annually.

The Old Faithful Inn, built in 1903–1904 from local logs and stone, is the largest log structure in the world. Its lobby features a 26-meter stone fireplace and handcrafted balconies rising six stories. The inn is one of the great architectural achievements of the American National Park system and is a National Historic Landmark.

Key Facts

• Old Faithful erupts every 44–125 minutes (average ~92 minutes).
• Eruptions shoot water 32–56 meters high at 95.6°C.
• Yellowstone contains over 500 geysers — half the world's total.
• The Yellowstone Supervolcano's magma chamber lies 5–15 km below the surface.
• Old Faithful has erupted more than 1 million times since its 1870 discovery.

Fun Facts

• Old Faithful was named by the 1870 Washburn Expedition because it was the first geyser they observed erupting at regular intervals.
• The geyser's eruption interval has lengthened slightly over the past century, from an average of about 65 minutes in the 1950s to 92 minutes today.
• Old Faithful Inn's lobby is so large that the geyser can be viewed from the upper balconies.
• The water erupting from Old Faithful fell as rain or snow hundreds to thousands of years ago before percolating deep underground.

Final Thoughts

Old Faithful is both a geological marvel and a window into the immense volcanic forces beneath Yellowstone. Its remarkable predictability, combined with the staggering power of the supervolcano that drives it, makes it one of the most important natural landmarks in the United States.