Giant rocks

Mountains are like great, gray giants. The are huge chunks of rock that have been pushed up out of the earth. Some mountains stand all alone, but most are connected together. Long chains of connected mountains are called mountain ranges.

Mountains are not all alike. Many mountains are bare and rocky. Others have green forests and fields of grass growing on their sides. And most high mountains have snow on their tops all year around. This is because the air on a mountain top is usually cold enough to keep water frozen.

Scientists believe that most of the earth's mountains are many millions of years old. The newest are wrinkled, and have sharp, pointed tops. Older mountains are smooth, with rounded tops. These "old" mountains have been worn down by wind and rain during many millions of years.