Snow Line, the line, usually in mountains, above which there is permanent snow. Below the line, temperatures are sufficiently high during the warmest months to melt the covering of snow. Virtually nowhere is the snow line in a fixed position, for the altitude at which it occurs varies with the depth of the annual snowfall, exposure to the sun, steepness of the slope, and the direction and velocity of the wind. In general, the snow line decreases in elevation from the equatorial regions, where it lies as high as 20,000 feet (6,000 m), to sea level near the poles.
Depending on who you ask, urban sprawl is either the best thing that ever happened to growing families -- or the downfall of civilization and the environment as we know it. Learn about the history and consequences of this American phenomenon.
Some people like to honeymoon at Niagara Falls, while others go over the falls in a barrel. How do these geological formations come to be?