Ponds are generally small, shallow lakes that have a more uniform temperature. Salt and bitter lakes are most common in arid areas where water evaporates faster than it can be replaced, leaving high concentrations of mineral salts. The most famous such lakes are Asia s Caspian Sea, the Dead Sea and Utah s Great Salt Lake. Lake Natron is one of several soda lakes that lie in Africa s Great Rift Valley. Their salinity is caused by volcanic gases or fluids.
Lakes are important sources of drinking water, electricity and water for irrigation.
Some lakes also support commercial fisheries or are valued for recreation. North America s Great Lakes serve as an important transportation system. Living things are typically found in one of three lake zones. The shallower edges of a lake are called the littoral zone. Marsh vegetation such as cattails and water lilies often grow here.