English: Geysers are hot springs that episodically erupt columns of water. They occur in few places on Earth. The highest concentration of geysers anywhere is at the Yellowstone Hotspot Volcano in northwestern Wyoming, USA.

Tardy Geyser is a frequently-erupting member of the Sawmill Group in Yellowstone’s Upper Geyers Basin. It is located 19 meters southeast of Sawmill Geyser. They geyser has a subcircular basin with a centrally-located, funnel-like vent surrounded by a nicely pustulose geyserite platform. Ringing the platform is a splash pool that contains discoidal geyser beads, many of which have become cemented together. Tardy Geyser has two runoff channels. The more frequently used channel runs roughly southwest toward the Firehole River. The other channel extends northeast from Tardy’s basin, then heads east, then heads roughly south toward the Firehole River. This geyser usually has short-duration eruptions that last a few seconds to several minutes (for example, see: www.youtube.com/watch?v=BzE2z1ew-KE) - this happens when nearby Sawmill Geyser is active. During a “Tardy Cycle”, the geyser will erupt continuously for 1 to 3 hours with no Sawmill activity. At such times, Tardy Geyser is the dominant member of the Sawmill Group. The northeast-to-east-to-south runoff channel is used during Tardy Cycle activity.

The Sawmill Group significantly changed in early 2017. Sawmill Geyser, the dominant member of the group, was last seen erupting at the end of January 2017, and has been dormant ever since. Sawmill Geyser's dormancy has been accompanied by changes in other Sawmill Group features, including Tardy Geyser. Some features are inactive or near-inactive, others have become more active, or are engaging in atypical behavior.

Shown above is Tardy Geyser in near-dormancy in summer 2017. The splash pools and runoff channels are water-filled but relatively cool. Colorful microbial mats cover most surfaces. Water drains from Tardy in both runoff channels. Reported and observed eruptions since early 2017 have been brief, with diminutive, splashing water columns.