[4] Pump Geyser erupts almost constantly making splashes 2 to 3 feet high, and thumps without an apparent interval, though there are less productive periods.

Then, in 1990, Pump became a true geyser, with intervals and durations of a few seconds.

[5] It was most likely named by Frank Jay Haynes, the park photographer from 1883 to 1916.

[6] It gets its name because its constant eruptions make a sound similar to that of old style mechanical pump.

Then, when Sponge drains, after a few seconds, Pump begins spurting again.