Book 4, Question 84
Why Do Lakes Freeze From the Top?
Ice is lighter than liquid water, so it floats! Cold air nips the surface first, and the ice lid then covers the water below like a blanket. That means fish can keep living underneath.
From the book
Page from A Million Whys Book 4
More fun facts
- As cold air cools the top of a lake, that water gets heavier and sinks, pushing warmer water up.
- Once the lake has cooled, a layer of ice forms on top.
- The ice works like a blanket, keeping the deeper water warm enough to stay liquid.
- Fish and other animals can live through winter in the liquid water under the ice.
- Ice and snow on a lake block sunlight, which can slowly lower the oxygen in the water over winter.
- In February 2014, ice covered 88 percent of North America's Great Lakes.
Sources: NASA, NASA Science
Questions kids ask
Do fish freeze in winter?
Usually not. The ice on top keeps the water below from freezing, so fish can keep swimming underneath.