Niland Geyser, Moving mud volcano in Imperial County, United States.

Niland Geyser, designated W9, is a mudpot about 5 miles northwest of Niland in the Salton Trough, near the Wister fault. It releases mud, water, carbon dioxide and small amounts of hydrogen sulfide gas. By late 2018 it had formed a basin of roughly 24,000 square feet, about 25 feet deep, with several small mud pots inside.

The mud spring appeared around 1953 about 5 miles northwest of Niland and stayed in place for over fifty years. It began shifting in 2007, and by 2018 it had moved 73 metres; satellite images showed a faster south-west drift from 2015 or 2016. In March 2021 it changed direction to the north-west, forcing the SR 111 bypass to be extended.

The mudpot's nickname, the "Slow One", alludes to the expected Big One earthquake, and it is formally designated W9 after the 2008 survey by David Lynch and Kenneth Hudnut. It sits on private land, and in 2019 sightseers were explicitly warned not to approach the mudpot.

Access is restricted because of hazardous gases and unstable ground, so visitors should keep their distance from the active areas. Follow any instructions provided at the site and pay attention to marked boundaries.

The geyser's nickname, the "Slow One", alludes to the expected Big One earthquake. It moves perpendicular to the fault lines near the Wister fault, an extension of the San Andreas Fault, and by late 2018 had carved a 24,000-square-foot basin.