Imperial first erupted in 1927. There was a hot spring at this location prior to 1927 but the eruptions greatly enlarged the crater. These early eruptions were quite large, often approaching 75 feet in height and over 30 feet in width. It discharged a large amount of water during its two-hour duration. Unfortunately, this activity only lasted about two years and then Imperial went quiet. Since then, Imperial has had periods of activity and inactivity; some of these periods have lasted decades.
In 1997, a side vent of Imperial activated. This activity, shown in the accompanying image, was characterized by nearly constant bursting play, some reaching nearly 50 feet. More recently it has been the site of brief, intermittent play lasting some seconds at a time, punctuated by quiet periods lasting about as long as the bursts themselves or a bit longer, so that it is erupting half the time or slightly less. Heights are commonly listed as 20 to 60 feet; however, the author of this description has seen bursts that he estimated as approaching 70 feet, and one that might have reached 75. Rigorous measurements of eruption heights from "New Imperial," as this side vent is sometimes called, would be appreciated.