Andy Hickey, age 7, of Chandler, Ariz., for his question:
HOW ARE CAVES FORMED?
Dark caves and cool underground caverns are wonderful places to visit if they are open to the public. Sometimes, however, foolish children and inexperienced adults go exploring in strange caves. Sad to say, many of these daredevils get lost or trapped, and some lose their lives. Wise amateur explorers always visit a safe cave one open to the public with lights and guides to help point out the scenery.
Great caves dot the earth's crust around the world. Some of them are formed as ocean waves beat against massive rocks. Year after year the crashing weight of the water grinds away at the cliffs, using bits of sand and pebbles to carve out a cave. Caves formed in this way are called sea caves. One of the largest North American sea caves is Sea Lion Cave in Oregon. Within its dark recesses can be found great herds of sea lions raising their families.
Other caves form when rivers of hot molten rock flow from a fiery volcano. Even though the surface of these lava rivers may cool and form a hard crust, the seething rock below flows on. When finally the lava flow ends, hollow tubes are left behind that form long lava caves.
Most of the earth's caves and caverns are formed in a special kind of rock called limestone. Limestone feels hard when you touch it, but actually it is one of the softest of rocks. Limestone can also be dissolved by a weak solution of carbolic acid. And this cave making liquid is quite plentiful in nature.
Each time it rains, countless millions of tiny raindrops pelt the earth. During their journey from the heavens they pick up carbon dioxide molecules from the air, becoming droplets of weak carbolic acid. Caves begin to form when the rainwater seeps through cracks or tiny pores in underground limestone rocks. Day after day, and year by patient year, the limestone dissolves like sugar in a glass of lemonade.
At first the softer portions of the rock dissolve, leaving large, darkened caverns. Where the rock dissolves more slowly, narrow passages form. After many thousands of years, a series of rooms connected by smaller tunnels may form. Scientists think that Carlsbad Caverns in New Mexico had its beginning this way some 60 million years ago. This cave's largest room could hold 10 football fields, and at one place its ceiling is as high as a 30 story building.
There are plenty of caves that offer safe, guided tours to the public. But there are just as many caves that are unsafe. No sensible person goes exploring caves without expert advisers and all the necessary equipment. Who knows, one of these may tumble down at the slightest disturbance. And Andy certainly would not want you to be there when it did.