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Steam rises from Excelsior Geyser in Yellowstone's Midway Geyser Basin. Excelsior was once the largest geyser In the world with numerous eruptions up to 300 feet. The last known major eruptions occurred during the 1880s when a violent eruption  may have damaged the siliceous sinter lining, allowing gas leakage and the loss of thermal energy. In 1985 it erupted for 2 days but only obtained a height of 20 to 80 feet.