GLACIERS

GLACIERS:

A river of ice inches down a valley in the Himalaya Mountains. This moving ice is called a glacier. If formed over many years, as snow collected near the peaks and the crystals turned to ice. As more snow fell, the ice grew so thick that began to move under its own weight. A glacier wears away mountainsides as it moves.

BIRTH OF AN ICEBERG:

In a cloud of spray, a chunk from a glacier crashes into the sea. The "birth" process is called calving. The "Calf" - a giant chunk of ice-is an iceberg. A giant ribbon of ice winds among the rocky peaks. The ice looks firm and till-but its's on the move. How do you know? Once in a while the ground shakes slightly, and a rumble like distant thunder breaks the quiet. The ribbon of ice is actural river of ice. It's a glacier. Glaciers form in parts of the world where snow piles up faster than it melts-in mountaines or in other areas that stay could most of the year. Over time, the snow crystals change to ice. When the ice is thick enough, its won weight causes it to move. The buildup may take a few years or hundreds of years. Once in motion, the ice creeps down a slope, perhaps traveling only an an inch a day.

In Greenland and in Antarctica Glaciers called ice sheets cover thousands of square miles. Most glaciers are smaller and form on high mountains such as Alaska's Mount McKinely.

Scientists have found that different parts of the same glacier move at different speeds. The sides and bottom of the moving ice grind against mountain walls. So these parts move more slowly than does the ice in the center. Gradually the sections pull apart and the ice cracks, forming deep canyons, or crevasses. Ice scapes White areas on the map show glaciers acound the world. Such ice spreads across one-tenth of the earth's land. It occurs on mainland and on islands. The largest glaciers, called ice sheets, lie in polar regins-in Greenland and in Antarctical. They are about two miles thick in places.

ICESCAPES:

Ice spreads across one-tenth of the earth's land. It occurs on mainlands and on islands. The largest glaciers, called ice sheets, lie in polar regions-in Greenland and in Antarctica. They are about two miles thick in places.

MASTER MOUNTAIN CARVERS:

Glacier changes the world. The painting shows how. Glaciers often form at the heads of valleys high in mountains. There snow piles up year after year, changing into ice. When the mass of ice is thick enough, it begins to move as glacier. It pries out rock and boulders, gradually carving a huge, bowl shaped hollow called a cirque(sirk). As it creeps down hill, the glacier scrapes the valley floor and mountain walls. During the glaciers's slow slide, other glaciers may join it. All have picked up tons of rock and dirt. Such debris shows as dark streaks on surface of water. In this art, part of a glacier has been cut away to show the debris inside. Continuing its slide, the glacier and the rocky material along its edge grind against the mountains sides. This forms deep, U-shaped valley that will remain long after the glacier has melted.