Cathy Conrad, age 13, of Spokane, Wash„ for her question:

Is it true that icebergs are made of fresh water?

An iceberg is made from white flurries of snowflakes and snow is made from the freshest of fresh water. The story may begin in the north polar regions, on the high slopes of Greenland's fagged mountains or in the southern Antarctic. In these places, the summers are short and they may be quite warm. But they are not long enough to melt all the snow which fell during the winter. The winters are long and cold and snow falls day after day, piling up in deep layers and drifts.

These conditions build up a glacier. It may be a tongue of ice on the rocky shoulders of a mountain in Greenland. It may be a flat field of ice in Antarctica. But it is made from the fallen snows of many winters. The deep layers are under heavy pressure from above. There are spring thaws which melt or partly melt the surface snow then comes a frosty spell to freeze it into solid ice.

Though a glacier is originally made from flurrying snowflakes, it becomes a solid mass of hard, dense ice. Ice is a mineral, though more fragile than the minerals from which most stones are made. The glacier labors under stresses and strains. It cracks and moves. The flat ice field moves out from the center in all directions, spreading like argiant puddle on the face of the earth.

The mountain glacier inches down the slope like a frozen river. Some glaciers move several feet in a day, others move only a few inches in a few weeks. But the edge of every glacier is always moving forward. And this is where the iceberg comes into the story. For every iceberg is the daughter of a glacier.

Some of the ice fields of Antarctica push down to the sea and face the waves with cliffs of ice and a hundred feet high or more. These chilly ocean waters are rough and wild.

Pounding waves beat at the icy cliffs day and night. The 'Lees a fragile mineral, is weakened.    The seas cut deep grooves under the cliffs. Finally a great chunk of ice groans and creeks to fall into the sea.  It is now launched as an iceberg.

Many of Greenland's glaciers dip down the slopes t o meet the sea. Here too the pounding waves weaken the ice and great chunks tumble into the water to become icebergs. They too were made of fresh water snow flakes which fell perhaps high on the mountain. They became ice and the ice was pushed toward the sea while new snows fell to make more glacial ice high on the mountain. All icebergs are at the mercy of the tides, the winds and the currents. Greenland's icebergs era swept down into the Atlantic Ocean where they melt, adding the fresh water to the salty sea,