Travel Reference
In-Depth Information
Grand Prismatic Spring
What Makes the Colors?
Wandering through Yellowstone's thermal areas, you'll see an amazing range of colors. The
centers of the hot springs may be deep blue or blue-green or palest turquoise blue. The
edges of the pools and their runoff channels will range from yellow through orange and
red to brown, with light and dark greens here and there. What causes these different col-
ors?
Let's start with the blue of the water. Sunlight penetrating the pool is scattered by the
minute particles and molecules in the water. However, blue light is scattered more effi-
ciently than red or yellow, so the light coming toward you appears blue. This same phe-
nomenon occurs in the atmosphere to give us blue skies. Thus, in all but very shallow hot
springs, we see blue centers. The blue is intensified in many pools where a lot of silica is
suspended in the water. Pools like Emerald Pool in Black Sand Basin (
page 72
) appear
green, combining their yellow or orange microorganisms with the blue water.
Scientists have found many different tiny living organisms in the hot springs, all gener-
ally called thermophilic microorganisms, meaning that they reproduce and prosper in hot
places. Different species of bacteria,
algae (Eukarya),
and
Archaea
thrive at different tem-
peratures and at different degrees of acidity or alkalinity.
Hyperthermophiles,
that is, organ-
