Grotto Geyser, #07205

Grotto Geyser, located in the Upper Geyser Basin, is named for its oddly-shaped sinter cone, possible formed around old tree stumps. Grotto Geyser erupts with intervals of approximately eight hours, and eruptions span from two to more than 24 hours with initial heights of 30-40 feet (10-13m) and sustained heights of 10 feet (3m) or more. Grotto Geyser is a fountain-type geyser, erupting through a pool contained within its sinter cone. Observers have noted two principal eruption modes for Grotto Geyser: short and long. Short mode eruptions are typically associated with, and terminated by, activity at neighboring Rocket Geyser. Long mode eruptions are more often associated with activity at nearby Spa Geyser as well as a sinking water level at Marathon Pool. Indeed, these associations are due to underground connections between these features, along with several other geysers, which together form the Grotto Geyser Group. The Grotto Geyser Group is easily reached on the flat 1.5 mile walk from Old Faithful Inn to Morning Glory Pool.

Sinter cone of oddly-shaped Grotto Geyser, thought to be formed over ancient tree stumps. Upper Geyser Basin, Yellowstone National Park, Wyoming, USA

Location: Upper Geyser Basin, Yellowstone National Park, Wyoming
Image ID: 07205
Format: Digital 3:2