Ann Merton, 13, of Baton Rouge La., for her question:
WHERE IS THE WORLD'S LARGEST CAVE SYSTEM?
Mammoth Cave National Park surrounds Mammoth Cave, part of the world's largest known cave system. Mammoth Cave is often called one of the wonders of the Western Hemisphere.
The cave system lies in central Kentucky, about 100 miles south of Louisville. The national park includes 51,354 acres of wooded hill country. Two rivers, the Green and the Nolin, flow through the park.
Mammoth Cave National Park was established in 1941. Almost two million visitors come to the park each year.
The famous cave is located in a ridge that consists mainly of limestone. Through millions of years, mildly acidic water trickled through cracks in the limestone and wore it away, forming the cave.
Visitors can be guided through 12 miles of corridors on five levels in the cave. The lowest level lies 360 feet below the surface of the earth. Many rocks in the cave have interesting colors and shapes. These rocks resemble flowers, waterfalls and trees.
Inside the caves are several lakes, rivers and real waterfalls. The largest river is called the Echo River and it varies in width from 20 feet to 60 feet and in depth from five to 25 feet.
Strange eyeless fish live in Echo River. These colorless creatures are about three inches long. Other blind creatures living in Mammoth Cave include beetles and crayfish. Several species of bats live in parts of the cave that are not visited frequently by people.
The first white men to see Mammoth Cave were local settlers who came to the area during the late 1700s. A deed filed in 1798 describes a large cave that probably was Mammoth Cave.
Moccasins, simple tools, torches and the remains of mummies found in the cave indicate that Mammoth Cave was known to prehistoric Indians.
Saltpeter used to make gunpowder, was mined in the cave during the War of 1812. Mammoth Cave contained the only large supply of saltpeter that was known in the United States at that time.
After the war ended, miners stopped working in the cave. It became a public showplace in 1816.
Another famous cave Floyd Collins Crystal Cave, lies within the national park. Collins, a cave explorer, discovered Crystal Cave in 1917. Crystal Cave forms part of the Flint Ridge cave system, one of three cave systems in the park. The other two are the Joppa Ridge and the Mammoth Cave system.
In September, 1972, explorers discovered a connection between Mammoth Cave and the Flint Ride cave system. The combined Flint Mammoth cave system stretches over 170 miles and is the longest known cave system in the world