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the super-heated water below, causing it to flash
into steam. That flash, that explosion through a
narrow, constricted place in the rocks, is what
sends water shooting into the air.
Hot Spring:
Hot springs are similar to geysers,
but they have no constrictions in their plumbing.
Convection prevents water from reaching the
temperature needed to set off the chain reaction
leading to an eruption. The many beautiful
colors you see in hot springs are caused by light
refraction, suspended mineral particles, and
heat-loving microorganisms.
Fumarole (also called a steam vent):
In simplest
terms, a fumarole is a vent in the Earth’s crust.
Modest amounts of groundwater come into
contact with hot rocks underground and are
turned to steam. This steam rushes up through
a series of crack and fissures and out the vent,
sometimes with enough force to create a loud
hiss or roar.
Mudpot:
Mudpots occur in places where
microorganisms help convert hydrogen sulfide,
which rises from deep within the earth, into
sulfuric acid. The acid dissolves surrounding
rock into clay, which mixes with rising steam and
groundwater to form mud of varying colors and
consistencies.
HIKING AROUND THE PARK
AND THERMAL FEATURES
We invite you to spend a few hours hiking the
area’s scenic trails. The thin ground in the
thermal areas breaks easily, and often overlies
scalding water. Stay on the trail. There are
numerous trails suitable for day hiking. Begin
your hike by stopping at a Ranger Station or
Visitor Center for information. Trail conditions
may change suddenly and unexpectedly. Bear
activity, rain or snow storms, high water, and
fires may temporarily close trails. At a minimum,
carry water, a raincoat or poncho, a warm hat,
insect repellent, sunscreen, and a first aid kit.
It is recommended that you hike with a party of
three. No permit is required for day hiking.
FOUR TYPES OF THERMAL
FEATURES
Geyser:
A geyser is a hot spring with the
intriguing habit of tossing underground water
in the air. It’s the equivalent of a giant pressure
cooker; even though the temperature of water
deep down may be well above boiling, the weight
and pressure of the water above prevents that
boiling from happening. Eventually, though, the
pressure builds enough to push the water in the
upper reaches up and out, causing an overflow.
That overflow, in turn, relieves the pressure on
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Thermal Features In Yellowstone