Yellowstone National Park
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Medusa Spring

Medusa Spring occurs in the far south-western portion of the Back Basin at Norris and can be seen from the highway. At present, Medusa is a spring which gently erupts overspilling its margins and flowing down the sinter terrace. In the past, Medusa has shown sporadic geyser activity. This feature is off-boardwalk and requires expert Ranger guidance to visit.

The vent and pool of Medusa Spring

This picture illustrated the vent and pool of Medusa Spring. Note the shallow pools of standing water around the outer rim of the vent and also the orange, brown and green colours in the vent.

The concentric rings of rubbly geyser "biscuits" and geyser "eggs" are also lines of evidence to suggest that Medusa showed geyser activity in the past. Study of newly formed features in the National Park at Potts Geyser Basin (on the shoreline of Lake Yellowstone) suggest that these may be strand lines of floating organic debris blown or washed into the pool. Eventually they silicify to form these structures and may be further enhanced by silica deposited as splash texture over the top.

The double vent of Medusa Spring

For the brave-hearted, here is a picture looking down into the double vents of Medusa Spring. Note how the sides of the vents have a knobbly texture, somewhat smoothed by water action. This is a splash texture remaining from when Medusa exhibited geyser activity.

Medusa Spring (legs for scale)

This photograph illustrates the concentric rings of material surrounding the vent of Medusa. Note: human legs for scale!