Groundwater - The Changing Earth: Exploring Geology and Evolution - page 348

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Figure 13.19 Hot Springs

a One of the more colorful hot-springs
in Yellowstone National Park, the Morning
Glory hot-spring is fringed with multicolored
mats of heat-loving, cyanobacteria and
algal mats. Each color represents a
certain temperature range that allows for
specifi c bacterial species to thrive in this
extreme environment.

c Mud pot at the Sulfur Works, also in Lassen Volcanic
National Park.

d The U.S. Park Service warns of the dangers in
hydrothermal areas, but some people ignore the warnings
and are injured or killed.

b The water in this hot spring at Bumpass Hell in Lassen Volcanic
National Park, California, is boiling.

The heat for most hot springs comes from magma or
cooling igneous rocks. The geologically recent igneous ac-
tivity in the western United States accounts for the large
number of hot springs in that region. The water in some
hot springs, however, circulates deep into Earth, where
it is warmed by the normal increase in temperature, the

geothermal gradient. For example, the spring water of
Warm Springs, Georgia, is heated in this manner. This
hot spring was a health and bathing resort long before the
Civil War (1861-1865); later, with the establishment of the
Georgia Warm Springs Foundation, it was used to help
treat polio victims.