Lakes form wherever there is a depression in the land and enough water to fill it. At first the water will sink into the ground. Once the ground is full of water, like a wet sponge, the water starts collecting above the ground in a lake.

Lakes are usually full of freshwater, but a few lakes, like the Great Salt Lake in Utah, have salty water.

Lakes can be large or small. Some are so large that when you stand on one side you can’t see the land on the other side! Lake Baikal in Siberia holds the most water of any lake in the world. It is over 600 km (almost 400 miles) long and almost two km (over a mile) deep!