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.