Clepsydra geyser

Clepsydra geyser, a photo by sachinvijayan on Flickr.

Via Flickr:
Clepsydra Geyser is a geyser in the Lower Geyser Basin of Yellowstone National Park in the United States.
Clepsydra plays nearly continuously to heights of 45 feet (14 m). Named by T. B. Comstock during the 1878 Captain Jones expedition. The name Clepsydra is derived from the Greek word for water clock. Prior to the 1959 Yellowstone earthquake, it erupted regularly every three minutes.