The majority of world's active geysers are in the Upper Geyser Basin, including Old Faithful. Only four other locations in the world have large concentrations of hydrothermal features: Russia (Kamchatka), Chile, New Zealand, and Iceland.

The heat for the hydrothermal features comes from Yellowstone's volcano. Molten rock or magma may be as close as 3-8 miles (5-13 km) under ground. Rain and snow supply water that seeps downs several thousand feet (more than a kilometer) below the surface where it is heated.

Underground cracks form the third ingredient: a natural "plumbing" system. Hot water rises through the plumbing to produce hot springs and geysers.

Rangers forecast the eruption times of five geysers here: Old Faithful, Castle, Grand, Daisy, and Riverside.

Use Caution in Thermal Areas

- Stay on boardwalks and trails.
- Thermal water can severely burn you.
- Never run, push, or shove.
- Supervise children at all times.

**You are responsible for your safety.**

**Think Safety, Act Safely. Yellowstone is a Dangerous Place.**

Accessibility

Wheelchair-accessible walkways lead from all parking areas to Old Faithful Geyser, and from the visitor center to other hydrothermal features.