Why do lakes and rivers only freeze on the surface and not all the way through?
In: 10
1. The air is what gets cold, the ground is almost always a couple degrees above freezing, so the lake cools from the top down.
2. When a part of water freezes, it floats to the surface no matter where the ice forms, this is due to ice being less dense than water.
3. Once the surface is frozen it acts as an insulator for the rest of the water below.
This mechanism is very important for life in the water. If it froze all over, fish would have a very bad time over the winter.
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