Which term describes layering of water based on temperature?

• A. Stratification
• B. Epilimnion
• C. Thermocline
• D. Neuston

Answer: (A)

Thermal stratification describes the layering of water by temperature in a lake, because warmer water is less dense and sits on top of cooler, denser water. This creates distinct layers: the warm upper layer (epilimnion), the cooler middle transition zone with rapid temperature change (thermocline or metalimnion), and the cooler bottom layer (hypolimnion). The other terms refer to parts of this structure or to surface-dwelling organisms (neuston), not to the overall layering process. In summer, lakes commonly show stratification, and turnover during spring or autumn mixes the layers again.