Brian Mellberg, age 13, of Huntsville, Ala., for his question:

HOW MUCH LAND IS THERE ON EARTH?

Lakes, rivers, oceans and all of the other bodies of water and ice on earth make up an area called the
hydrosphere. The waters of the hydrosphere are important to man and plants since they need water to live. Plants also use the water to make food, and then they are eaten by man and animals. Large bodies of water also help to control the earth's weather and climate.
About 70 percent of the earth's surface is water, which means that only about 30 percent is land. The solid part of the earth that is out of water covers about 57,280,000 square miles. In square kilometers, that's 148,350,000.
Land comes in all types of material including rocks, sand, minerals and soil. And it comes in a wide variety of shapes, too, including continents, plains, plateaus, hills, mountains, valleys, mesas, canyons and buttes.
A geographer will think of the land as a specific region. The economist will think of it as the natural wealth of the earth from which all good things are produced.
And the farmer will think of the land as the soil where he will grow. crops.
Altitude of the world's land varies from a large amount that is only a few feet above sea level to high country located on a large number of mountains. Highest point of land is Mount Everrest in Asia with its altitude of 29,028 feet above sea level. The lowest point on earth is the shore of the Dead Sea in southwest Asia which is 1,299 feet below the level of the sea.  Average altitude of the world's land is 2,757 feet above the level of the oceans.
Largest of the world's land masses are called continents. The surface of these large bodies of land vary from low ground and green valleys to mountain meadows and rocky bluffs. Antarctica, the continent at the South Pole, is always completely buried under snow and ice while thick forests in Africa and South America near the equator are always hot. The world's land temperature goes all the way from 136 degrees Fahrenheit, the highest temperature ever recorded, to minus 126.9 degrees Fahrenheit, the record figure for a low temperature. High honors go to A1'Aziziyah, Libya, while the low award goes to Vostok in Antarctica.
The region where life is found on the earth's surface is called the biosphere.
Scientists say that the earth formed at least 4.5 billion years ago and at about the same time as other planets were formed. They have found rocks that are almost 3.5 billion years old, and they say the earth itself must be at least 1 billion years older than these rocks.