Tommy Baker, age 13, of Laconia, N.H., for his question:

HOW OLD IS CARLSBAD CAVERNS?

Carlsbad Caverns, a chain of huge underground caves located in southwestern New Mexico, became a national park in 1930. The limestone in the caverns is believed to have formed a shallow inland extension of the ocean about 200 million years ago.

Scientists tell us that when the Rocky Mountains were formed about 60 million years ago, the cavern area rose above sea level and water began hollowing out the limestone to form the caves.

The large chamber, now called the Big Room, is 4,000 feet long and 625 feet wide. At one point, the ceiling is 285 feet high.

Carlsbad caverns is famous for stalactites and stalagmites in various shades of white and pastel colors. There are also shapes like Chinese temples, heavy pillars and lacy icicles.

One part of the caverns contains millions of bats that fly out at dusk in warm weather in search of insects.