The earth is mostly rock. Three-fourths of its surface is covered by
a relatively thin layer of water (some of it frozen), and the entire planet
is surrounded by a relatively thin blanket of air. It is the only body
in the solar system that appears able to support life. The other planets
have compositions and conditions very different from the earth's.
| NSES Content Standard D
Earth and Space Science: Structure of the Earth system Grades 5-8, page 160 Water, which covers the majority of the earth's surface, circulates through the crust, oceans, and atmosphere in what is known as the "water cycle." Water evaporates from the earth's surface, rises and cools as it moves to higher elevations, condenses as rain or snow, and falls to the surface where it collects in lakes, oceans, soil, and in rocks underground. NSES Content Standard D
|