Lake turnover is the process of a lake's water turning over from top (epilimnion) to bottom (hypolimnion). During the summer, the epilimnion, or surface layer, is the warmest. It is heated by the sun. The deepest layer, the hypolimnion, is the coldest. The sun's radiation does not reach this cold, dark layer.

During the fall, the warm surface water begins to cool. As water cools, it becomes more dense, causing it to sink. This dense water forces the water of the hypolimnion to rise, "turning over" the layers.

dense
Adjective

having parts or molecules that are packed closely together.

epilimnion
Noun

surface and upper part of a lake.

hypolimnion
Noun

dense bottom layer of a lake.

Noun

body of water surrounded by land.

lake turnover
Noun

process of the dense lower layer of a lake rising to become the upper, less-dense layer.

radiation
Noun

energy, emitted as waves or particles, radiating outward from a source.