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 Geysers
are hot springs that erupt periodically. The
eruptions is the result of super-heated water
below-ground becoming trapped in channels leading to the
surface. The hottest temperatures are at the bottom of
these channels (nearer the hot rock that heats the water)
but the deep water cannot vaporize because of the weight
of the water above. Instead, steam is sent upwards in
bubbles, collecting in the channel's tight spots until
they essentially become clogged, leading to a point where
the confined bubbles actually lift the water above,
causing the geyser to overflow. This causes the pressure
to decrease until suddenly violent boiling occurs
throughout much the length of the column, producing a
tremendous volume of steam which forces the water out of
the vent in a superheated mass. This is an eruption. As
the eruption continues, the heat and pressure gradually
decrease, and the eruption stops when the water reservoir
is depleted or the steam runs out. The two types of
geysers are fountain geysers (which shoot water out in
various directions through a pool) and cone geysers
(which shoot water out in a fairly narrow jet, usually
from a cone-like formation).
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 Hot
Springs are similar to geysers, but their underground
channels are large enough to allow rapid circulation of
water. Rising hot water releases heat energy by
evaporation or hot water runoff, while convection
currents return the cooler water to the underground
system, thus maintaining equilibrium. The microorganisms
which live in and around the hot springs often make the
pools very colorful.
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Fumaroles are holes or vents from which steam rushes into
the air. It is like a hot spring, but lacks liquid water.
Either there isn't enough water or the underground rock
is too hat and boils off all of the water so a pool can't
form. The small amount of water that does seep into the
area is converted to steam and expelled from the vent,
oftentimes creating a hissing noise.
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Mudpots are thermal areas where water-saturated sediment
(similar to clay) is affected by super-heated steam
below. Rising steam forces its way upwards through the
mud and ground water, bursting upwards sending showers of
mud into the air, as if in a small explosion.
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Steam Vents are cracks in the surface of the ground through
which pressurized steam from below escapes to the surface, oftentimes
with a hissing sound.
Access a searchable database of all Yellowstone's thermal features,
courtesy of Montana State University and Yellowstone National Park. |
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