In the 1880s Excelsior Geyser erupted in bursts
50 to 300 feet high. The thermal violence formed
the jagged crater and apparently ruptured the
geyser's underground system, causing
eruptions to cease after 1890.
On September 14, 1985, Excelsior roared back to
life with forty-seven hours of major eruptions.
It is impossible to predict when this dormant
but powerful geyser's next eruption will occur.
Frank J. Haynes photographed this eruption in
1888. Like most geysers, Excelsior is unpredictable,
with no discernible pattern to its eruptions.
Though its eruptions have been
erratic, the geyser's outflow is
nearly constant, pumping more
than 4000 gallons of boiling
water per minute over the crater
rim into the Firehole River.