Excelsior Geyser erupting as a violent hydrothermal explosion. The ...

Excelsior Geyser erupted in a series of violent hydrothermal explosions in the 1880s and early 1890s; one of these eruptions is shown in this colorized postcard made from a photograph. These were the largest such events to occur in the Yellowstone region in historical times. (Original photograph by F. Jay Haynes, 1888; date on postcard is incorrect.)