My friend Joe from Bozeman, Montana, has come up for the weekend. We ski out to the Crater Hill Geyser, a thermal area that is visible from my house. The area is located four miles to the southwest in the Hayden Valley. The snow is good and the temperature is near zero degrees F. which is a comfortable temperature on a sunny windless day if you are active.

The ground in the thermal area is warm and thus is largely free of snow. Once we make landfall we can dismount from our skis and walk around on the earth, a treat in this snow covered landscape. Among the many wonderful things we see in the area is the Crater Hill Geyser whose pattern of activity has not changed since it was first documented in the early 1850s when it appeared on the first surviving map know of the Yellowstone area.

The geyser is in nearly constant eruption spilling waves of hot mineral saturated water over the edges of its surrounding crater. As the water cools it releases some of the silica it carries. The precipitated silica accumulates in spiney complexes of accreting mineral deposits. In watery pockets among these deposits are nests of “geyser eggs”, curious concretions that grow a new micro layer after each cyclical pulse of hot water.

A closer view.

The warm ground is generally bare of snow and is often visited by wandering herds of buffalo throughout the winter that are attracted to the area by the relief of not having to wallow through the three to six feet of snow that surround the thermal area. The buffalo pie forms an insulating platform where snow and frost can accumulate. On the surrounding warm ground any snow evaporates shortly after it falls.

The nuances of a warm spot of earth in the geyser area are revealed here on a hillside patch about forty by forty feet in extent.

The trench in the snow was made by two young buffalo bulls near the snowmobile trail up to the house. At the left edge of the furrow the tracks of a coyote show where the canny canine took advantage of the higher density of snow created by the passage of the buffalo. This snow is easier to walk on than the virgin powder on either side of the post holed trench. Further to the left are the tracks of a pine marten, one of a pair of big aboreal weasels that live near the house and which like to run around in the attic in the middle of the night.