Stone icicles
Many a cave is filled with what look like giant stone icicles. Some of
these “icicles” hang down from the cave’s roof. Others stick up from the
floor. They are often as thick as tree trunks. Sometimes, the ones on
the ceiling and the ones on the floor meet to form thick pillars. These
strange-looking stone “icicles” are usually found in limestone caves.
The “icicles” that hang from the ceiling are called stalactites. They
are made by water trickling through cracks in a cave’s limestone roof.
The water carries tiny bits of the mineral called calcite with it. As
some of the water dries, it leaves bits of calcite stuck to the ceiling.
Each drop of water adds more calcite. Slowly, as more bits of calcite
are added, the stalactite grows longer and longer.
Some of the water drips to the cave floor. This water also has bits of
calcite in it. As the water dries up, bits of calcite are left on the
floor. Slowly, the calcite piles grow higher and higher. These “icicles”
sticking up from the floor of a cave are called stalagmites.
Often, water drips off a stalactite onto the top of a stalagmite below
it. Slowly, the two grow toward one another until they finally join.
Many people get stalactites and stalagmites mixed up. They can’t
remember which hangs from the ceiling and which sticks up from the
ground. But there is an easy way to remember. Just remember that
ceiling begins with c, and stalactite has a c in it. And ground
begins with g, and stalagmite has a g in it. Then you’ll always
know that stalactites hang from the ceiling and stalagmites stick up
from the ground.
