The term cave
is given to a naturally formed underground cavity. The term usually
implies that the opening is large enough for a person to enter
and may indicate a length further than sunlight reaches. Some
caves measure a few hundred feet while others extend for many
miles and reach hundreds of feet in depth. Caves can be found
in many parts of the world and in every state in the United States.
Caves are geological features and form in a variety of ways.
most common caves are solutional caves, often called limestone
caves for the common type of soluble rock in which they form.
This is the type of cave seen in the Journey into Amazing Caves
movie in the canyon areas and the cave diving scenes. Both the
terrestrial and underwater caves in the film are solutional or
limestone caves. Most limestone caves form through the dissolution
of soluble rocks by a weak, naturally occurring acid in groundwater.
The minerals which make up the rock actually dissolve into groundwater,
like sugar into hot tea, but much more slowly. The caves form
as groundwater dissolves quantities of soluble rock by seeping
along joints, faults and along bedding plains. In time the cracks
enlarge to form cavern systems.
these solutional caves are flooded with groundwater. This happens
when the level of the groundwater, or watertable, is above the
level of the cave passage. The underwater cave in the Journey
into Amazing Caves movie was in this type of flooded cave
passage. The entire cave can be filled with water, or only the
cave passages below the water table will be filled with water.
caves are decorated with cave formations called speleothems. These
speleothems are formed as calcite is deposited on the surface
of cave ceilings, walls and floors. The most commonly known speleothems
are stalactities, which hang on the ceiling, and stalagmites,
which grow up from the floor.
For more information
on speleothems including some great pictures visit The Virtual
Cave - http://www.goodearthgraphics.com/virtcave.html
of cave in Journey into Amazing Caves movie film are ices
caves. Ice caves can form under glaciers. Melting water running
under the glaciers or through cracks in the glaciers can erode
and melt tunnels or chambers in the ice. Ice caves can also be
caves in rock which have a temperature below freezing all year.
These caves have ice forming on the ceiling, walls and floors.
other cave types would include lava caves, sea caves
and sandstone caves.