is the tallest geyser on Earth to have a predictable eruption, its waters reaching heights of up to 200 feet in a short series of bursts (one to five) , separated by between 7 and 15 hours of inactivity. Eruptions typically last for ten minutes, and are followed by gradual replenishment of the 30 foot diameter pool above the vent. Although predicable to a degree, times are subject to an uncertainty of two hours plus or minus, so some patience may be needed to witness an eruption.
When inactive, the geyser is not so interesting to look at since the pool is quite far from the path (100 feet), though it is surrounded by large, moderately colorful sinter terraces, and a 30 foot wide run-off channel flows west, under the boardwalk trail towards the Firehole River. The pool lies right at the east edge of the Upper Geyser Basin, bordered by steep, wooded slopes. Grand is one of five geysers in the basin for which activity is predicted.
Back to map of the Upper Geyser Basin