There are two types of tundra: Arctic and alpine. Arctic tundra is found near the Arctic Circle. Alpine tundra forms on mountaintops where the proper conditions are found.

Arctic Tundra

Several characteristics are typical of Arctic tundra. One is the polar climate, which has an average July temperature of not more than 50°F (10°C). Because Arctic tundra is far from the equator, sunlight hits the Earth here at an angle and must therefore pass through more atmosphere. This means the sunlight that reaches the soil contains less energy per square foot (square meter) than at the equator.

Another characteristic of the Arctic tundra is a deep layer of permanently frozen ground. Generally, less than about 18 inches (45 centimeters) of tundra soil thaws during the cool summer. Below that the ground remains frozen. Water from melting snow cannot drain into the frozen ground, and little evaporates...