Larry Sidebottom, age 13, of Fairfield, Conn., for his question:

Why does a mountain to sometimes look like a pile of stones?

America's oldest mountains are in New England. Their life story begins some 300 million years ago when almost half our continent lay under a shallow sea. Vast stretches of the land were covered in swampy forests    huge ferns and towering horsetails. Earthquakes and volcanoes shook the eastern shores and gradually a chain  of high mountains lifted their noses above the strange landscape. They were the start of the northern branch of the Appalachian Mountains in our New England states.

These mountains arose in time to see the first air breathing creatures gasp above the ancient seas. They saw the first spiders develop as land dwellers and the footprints of the first amphibians.

They were tall and lofty, and possibly carried crowns of snow upon their peaks.

Had they been able to observe, they could have read their future in the then crumbling Laurentians far to the north. For these Canadian mountains had lifted their noses above ground level a full 300 million years before the Appalachians. Today, only the root of the once tall Laurentians remain.

In a hundred million years or so, the southern Appalachians began to grow and extend the huge range from New England almost to the Gulf of Mexico. As the mountains slowly grew, they saw the seas advance over the center of the continent and then recede. They saw the age of amphibians come and go. They saw the great dinosaurs coming to power and the little mammals begin their history upon earth. Before they had completed their growth, the ferny forests had given way to palms and pines.

Also, before they were fully grown, the fate of the Laurentians had begun to overtake them. Wind and weather had begun the age long job of wearing down their tall towers to the level of the plains.

Ivy crowns tore at the jagged peaks, Tumbling rains washed away sharp edge$ and loose boulders. Pointed peaks were forced to become rounded domes.

Then cloudbursts, storms, snow, hail and gentle rains worked with lapping tongues for a million seasons. Water seeped through the porous rocks on its way to the rivers and sea. It dissolved chemicals and minerals, carried them away and left the rooks weakened. More water cut through the weakened rocks in rills and rivulets. Much of the softer surface rock was broken up and carried away by running water. In places, especially at the tops of once high mountains, the harder rocks below were left bare and naked to the weather.

Erosion, the wearing away by wind and weather, now takes longer than it did many ages ago. The slopes necessary for energetic torrents have become more gentle. The layers of exposed rocks are harder to break up.

    Heat and frost help the water to break up these giant slabs into boulders, pebbles and fragments. The rocky slabs become riddled with tracks as they expand in the sunshine and contract in the frost. Water trickles through the crevices, widens them and smoothes their edges. Season by season, bit by bit, the bare, rocky slab at the top of the mountain is worn into a heap of boulders and stones.