YELLOWSTONE NATIONAL PARK — While explosions are relatively common in Yellowstone National Park (YNP), according to the Yellowstone Volcano Observatory (YVO), Excelsior Geyser was especially active in the 1880s. Before the 2024 Black Diamond Pool explosion at Biscuit Basin, Excelsior produced the largest well-observed front-country hydrothermal explosions.
YVO Scientist in Charge Michael Poland writes in this week’s Caldera Chronicles that Excelsior Geyser is located in Midway Geyser Basin, adjacent to the famous Grand Prismatic Spring.
“The geyser may have formed sometime in the mid-1800s — it was not described by a trapper who visited and described Grand Prismatic Spring in 1839, but was present by 1871, when it was named ‘The Cauldron,'” Poland writes.
Activity at Excelsior Geyser in the late 1800s spanned geyser eruptions to hydrothermal explosions. Some activity ejected small rock fragments, according to Poland, while other events involved boulders and large plumes of material lofted high into the air. Poland suggests the first of these large eruptions was allegedly witnessed in 1878, but it was in 1881 to 1882 that well-observed eruptions sent material 30 to 110 meters (or 100 to 360 feet) into the air.
According to Poland, intervals between eruptions were as brief as an hour, and eruptions could last for up to several minutes.
“Water discharge from these eruptions was so great that the flow of the Firehole River noticeably increased when the geyser was active, and the plume from some eruptions could be seen 160 kilometers (100 miles) away because the steam created clouds,” Poland writes.
Park Superintendent Philetus W. Norris apparently named the geyser Excelsior for its impressive, powerful and even violent eruptions.
Poland confirms Excelsior then went dormant by late 1882; it might have erupted once or twice sometime between 1883 and 1887, but activity resumed “with vigor” in 1888. Poland writes that during a series of eruptions, some of which were photographed, rocks 30 centimeters (1 foot) across were thrown a distance of 150 meters (500 feet).
These large-scale eruptions and explosions continued into 1890, when Excelsior then entered another period of dormancy that lasted almost 100 years. Poland does note, however, that there could have been some additional activity in 1901.
Excelsior woke once more over a 46-hour period during Sept. 14 to 16, 1985. Poland explains that eruptions were much smaller than those of the 1800s, but still flung mud, lasted minutes and were separated by several minutes to about an hour.
“Since that time, no other activity, aside from some violent boiling in 2000, has been noted,” Poland writes. “This doesn’t mean that Excelsior is ‘done,’ of course.”
Poland emphasizes that, as with most Yellowstone geysers, Excelsior’s activity was and continues to be unpredictable.
