Thermal stratification is the layering of water in a body, such as a lake or ocean, based on temperature differences. Warmer water, which is less dense, sits on top of cooler, denser water. This phenomenon often occurs during seasonal changes, where the surface water heats up in summer and cools down in winter, creating distinct layers. These layers can affect aquatic life and water quality. For example, the upper layer, or epilimnion, is warmer and supports photosynthesis, while the lower layer, or hypolimnion, is colder and can become depleted of oxygen. Understanding thermal stratification is important for managing ecosystems and fisheries.