The southwest corner of Yellowstone Park contains several geothermal fields, including the
most famous one surrounding the geyser known as Old Faithful. The largest one is the Midway
field, in which most of the pictures below were taken.
Thermophilic microorganisms which contain carotene (orange) or chlorophyll (green) thrive in hot
water at specific temperature ranges, creating varying washes of color as water spreads outward
from the hot spring-fed pools.
One of the largest of the brilliant blue, steam-shrouded clear pools at Midway.
The Opal Pool in the Midway Geyser Field.
Across mats of microorganisms watered by it, the steam rises from the Grand Prismatic Pool.
Tourists walk above the surface flow spreading outward from the Prismatic Pool, a broad flow
which separates itself into shallow channels of varying colors.
Yet another view of the colored flows spreading outward from the Prismatic Pool.
Anne and Bob standing on the walkway in front of the Grand Prismatic Pool.
It was a cold and windy day.
Shannon on the walkway in front of ... well, there it is again.
An Old Faithful eruption seen from the observation point on the hill to the west of the
geyser mound and the lodge.
Old Faithful about 70 minutes later, an eruption seen from the usual location--the benches around
the geyser mound.
The pictures of this trip are divided into several sets: