To: Gregory, A. E. <GREGORAE@mail.aramco.com.sa>;
Date: Tuesday, February 22, 2000 8:58 PM
Subject: stalactites and stalagmites:

(From a Carlsbad related
Website:http://www.nps.gov/cave/teacherguide/activities.earth.html)

Dear Janet,

Speleothem is the name given to any secondary deposit (decoration) inside of
a cave.
Stalactites are speleothems that hang down from the cave ceiling,
and stalagmites are speleothems that rise up from the cave floor.
Formation of any speleothem takes a long period of time.
(...They are formed from the 'dripping' and 'drying' of water droplets which
contains dissoloved minerals (including calcium carbonate).)

As each drop of water leaves a tiny amount of mineral residue on a cave
ceiling, floor, wall or other feature, it adds to speleothem growth.

When a speleothem is broken, it will not be replaced within our lifetime, if
ever! Therefore, cavers should be extremely careful while exploring.

----

from encyclopedia britanica:  http://www.britannica.com/

stalactite and stalagmite
elongated forms of various minerals deposited from solution by slowly
dripping water. A stalactite hangs like an icicle from the ceiling or sides
of a cavern. A stalagmite appears like an inverted stalactite, rising from
the floor of a cavern.

Stalactites hanging from the ceilings of caverns commonly exhibit a central
tube or the trace of a former tube whose diameter is that of a drop of water
hanging by surface tension. A drop on the tip of a growing stalactite leaves
a deposit only around its rim. Downward growth of the rim makes the tube.
The simplest stalactite form, therefore, is a thin-walled stone straw, and
these fragile forms may reach lengths of 0.5 m (20 inches) or more where air
currents have not seriously disturbed the growth. The more common form is a
downward-tapering cone and is simply a thickening of the straw type by
mineral deposition from a film of water descending the exterior of the
pendant.

Stalagmites have thicker proportions and grow up on the bottom of a cavern
from the same drip-water source, the mineral from which is deposited after
the water droplet falls across the open space in the rock. Not every
stalactite has a complementary stalagmite, and many of the latter may have
no stalactite above them. Where the paired relation exists, however,
continual elongation of one or both may eventually result in a junction and
the formation of a column.

The dominant mineral in such deposits is calcite (calcium carbonate), and
the largest displays are formed in caves of limestone and dolomite. Other
minerals that may be deposited include other carbonates, opal, chalcedony,
limonite, and some sulfides.

Conditions that favour the deposition are: (1) a source rock above the
cavern; (2) downward percolation of water supplied from rain; (3) tight but
continuous passageways for this water, which determine a very slow drip; and
(4) adequate air space in the void to allow either evaporation or the escape
of carbon dioxide from the water, which thus loses some of its solvent
ability.

Information about this topic in other articles:

stalactite

Carlsbad Caverns National Park
Carlsbad Caverns National Park
from Carlsbad Caverns National Park

formation
Depositional materials and features
from cave