Dennis Vaper, age 10, Of Montgcmery, Ala., for his question:

Which is the world's largest mountain range?

Most geologists consider the mountain ranges of western America as one vast system. It stretches all the way frmm Alaska down to the tip of South America. In size, it is the largest mountain range we are likely to see. But the world has other mountain systems hidden below the waters of the ocean.

The largest undersea mountain system is the mid atlantic ridge. These vast ranges, twice as wide as the Andes, run down the center of the Atlantic Ocean, and most of its peaks are submerged under a mile or more of water. It begins near Iceland and follows the curves of the coastlines which border the Atlantic. At the tip of South Africa, the underwater ridge curves around into the Indian Ocean. In width and in length, the mid Atlantic ridge is the largest mountain system on our planet.