Volcanic Springs

Geysers, Hot Springs,
Mud Pots, and Fumaroles

Upper Geyser Basin, Morning Glory Group

North of Grotto and Chain Lakes Groups a bridge over Firehole River leads into the Morning Glory Group. Several important geysers are among the features gathering around the famous Morning Glory Pool. Above all to mention are Mortar Geyser and Fan Geyser, located directly past the bridge on the riverbank. They are connected subterranean and erupt almost always in concert. Both geysers encompass several vents, which are carrying names of their own. Fan and Mortar are cyclic geysers with a complex pattern of activity. Intervals reach from days to some weeks. Fan Geyser sends angled jets up to 38 m (125 feet) high, Mortar plays up to 15 m (50 feet).

Mortar Geyser in front, minor eruption of Fan Geyser ("High Vent" left and "Gold Vent" right) in background:

Mortar Geyser and Fan Geyser Yellowstone

Mortar Geyser and Fan Geyser Yellowstone

Fan Geyser, minor eruption of "High Vent" in center and "Main Vent" (vent itself is obscured) on the left side:

Fan Geyser Yellowstone

Fan Geyser Yellowstone
From the bridge you may also spot the perpetually spouting West Sentinel Geyser 200 m downstream at the river bend.

West Sentinel Geyser:

West Sentinel Geyser Yellowstone

West Sentinel Geyser Yellowstone
Spiteful Geyser lies north of Fan Geyser next to the trail. It is an irregularly and very rarely erupting geyser, whose bursts may reach 9 m (30 feet) height.

Spiteful Geyser (Fan Geyser left):

Spiteful Geyser Yellowstone

Spiteful Geyser Yellowstone
Across the trail from Spiteful Geyser the fenced off Norris Pool can be seen. Eruptions of considerable height occurred around the turn of the millenium.

Norris Pool:

Norris Pool Yellowstone

Norris Pool Yellowstone
The famous Morning Glory Pool is still a gorgeous sight, but far away from its pristine state. Objects, thrown into the pool by visitors, have almost clogged its vent and block the supply of hot water from the depth. As a result the brilliant blue color of the bowl has shifted to green and the once narrow yellow ring around the rim has broadened considerably. Several attempts of the National Park Service to re-enlarge the vent failed.

Morning Glory Pool:

Morning Glory Pool Yellowstone

Morning Glory Pool Yellowstone
North of Morning Glory Pool the trail continues in direction of the Cascade Group. After 100 m (330 feet) there is a branch-off to Firehole River, where you meet with Sentinel Geyser. Sentinel's bowl comprises two vents. The one on the southwest side is capable of erupting up to 6 m (20 feet), the one in the northeast up to 12 m (40 feet). However, eruptions of that size are rare. Usually Sentinel Geyser shows perpetual boiling with some higher splashes.

Sentinel Geyser:

Sentinel Geyser Yellowstone

Sentinel Geyser Yellowstone
On Sentinel's geyserite mound, a few feet south of its bowl, some small holes, called "Sentinel's Vents" are to be found. They frequently show splashing up to 1 m (3 feet).

Sentinel's Vents (on the left side):

Sentinel's Vents Yellowstone

Sentinel's Vents Yellowstone
Farther north the trail passes Green Star Spring beyond the river.

Green Star Spring:

Green Star Spring Yellowstone

Green Star Spring Yellowstone

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