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.
Sand dunes belch, moan and hum. They roll across the desert, seeking out new locales. You might even say they breed. It's no wonder people call these giant sand formations lifelike.
Continents aren't the unchanging, universally recognized land masses of our school studies. But they do help us make sense of our world. How did they get their names?