Joseph Kehl, aged 11, of Drexel Hill, Penna., for his question:
How and where are stalactites formed?
The story of stalactites is a story of give‑and‑take. Air, water, rocks and ancient shellfish all play a part in a long term loan. The story begins with rocks and ends with rocks. Hut the whole of it takes time ‑ several million years of time.
Rain has been falling since the world began. It fell upon the earth before any living creatures came to live here. It ran over the bare rocks, gathered in rivers and emptied into the ancient fresh water seas. But rainwater was a robber then, just as it is today. Its greedy little tongues lapped chemicals from the rocks and dumped them into the sea.
The first living things in the sea found all the chemicals they needed dissolved in the water and waiting for them. Billions of tiny creatures made shells from these chemicals. In time they .littered the _ sea beds with piles of old shells. These piles often dried, hardened and became part of the dry land.
Piles of tiny old seashells packed down to form layers of limestone. The chemicals borrowed from the rocks were returned as new rocks. This new limestone rock dissolves easily in water. Some of it. borrows the water again to form itself into still more fancy rocks. Most of the beautiful stalactites are made from limestone ‑ with the help of seeping water.
Pure rainwater is not too good at dissolving rocky chemicals It needs a little free oxygen and carbon dioxide. It gets these and certain acids as it seeps through the top soil. There may be a layer of limestone under the soil. If so, the rainwater from the spill is ready to seep down and lap it up. It dissolves the stone which was made from old seashells. It cuts out holes and tunnels below the level of the ground.
In time, this seeping water digs caves, caverns, and tunnels. Sometimes it drips slowly from a cavern ceiling. The water evaporates into the air, leaving its load of chemicals behind The chemicals harden into limestone again. Icicles of stone grow and grow. A delicate stalactite hangs from the ceiling. Maybe drips fall on the ground below it, As this puddle evaporates, it builds up a spike of stone ‑ a stalagmite. When stalactite and stalagmite meet they form a pillar of limestone.
The place to look for a stalactite is in a limestone cave. Some of the world's best are in Mammoth Cave, Kentucky. Others are in Luray, Virginia and Wyandotte, Indiana, Nearer home you may visit Crystal Cave between Allentown and Bethlehem, Pennsylvania. Workman discovered this while blasting for limestone. There they give and take between stone and running water is so beautiful that one cave is called the Cathedral Chamber,