Valerie Volf, age 11, of Omaha, Neb., for her question:

ARE ICEBERGS MADE FROM SALT WATER?

Some people think that icebergs must be frozen salt water because they float in the salty sea. But this is not so. Actually they are great chunks of frozen fresh water  and as they melt away they spread their fresh water around in the ocean. The story begins with snowfalls in the polar regions. The snow is made from fragments of frozen fresh water from the clouds.

Winter after winter, the polar glaciers add layers of frozen fresh snow  and the snow becomes packed into freshwater ice. A massive ice field spreads out under its own weight. Where the edges meet the sea, great chunks of this freshwater ice break off and go drifting away as icebergs.