Why Lake Tahoe Doesn't Fully Freeze

[PhysicsinCalifornia]

This is a physical intuition problem I don't quite understand fully.

The question is, why doesn't Lake Tahoe freeze (the whole Lake)?

I know the crystal structure for water breaks at 4 C and the volume is at its lowest point at that temperature.

If the temperature above the water is less than 4 C(say -11 C), why doesn't the whole lake freeze up?

 

[Adrian Baker]

Ice is a good insulator. The water at 4C therefore can't lose heat very well through the ice layer. As it does lose heat, the ice gets thicker, increasing the insulation.

 

[Mk]

That is exactly why fish can swim around under the ice and they don't solidify.

 

[Huckleberry]

The whole lake doesn't freeze up because ice floats. The ice forms on the top of the water and not on the bottom. Then as AB said, it insulates the water underneath it.

 

[PhysicsinCalifornia]

It is to my understanding that the whole lake WILL freeze up when the whole lake turns to 4 degrees celsius.

If this is true, I don't understand it(lol)

I understand that the ice will be the insulator for the lake, so the outside temp. will not directly reach the bottom of the lake instantly.(Maximum depth for Lake Tahoe is 501 meters, or 1645 ft., this is the second deepest in the US!)

So given a length of time, the whole lake will freeze up?(and turn into a glacier like the one that hit Titanic?)

Or does the bottom of the lake stay at a higher temperature because there is higher temperature down there, or closer to the Earth's center?

or am I just thinking too much over my head here?

 

[PerennialII]

Given suitable heat transfer conditions the whole thing will freeze up, happens typically and commonly to ponds etc. all the time.

 

[tcmacrae]

http://beetlesinthebush.wordpress.com/2009/04/08/myths-about-why-lake-tahoe-does-not-freeze/"

 

[russ_watters]

So given a length of time, the whole lake will freeze up?(and turn into a glacier like the one that hit Titanic?)

Remember, the Earth itself is warm underground, a constant temp of about 55 F once you are a certain depth underground (then rising as you go deeper). So the cold from above has to fight and overcome the warm from below to freeze a pond solid. It can happen, but it doesn't very often.

 

[russ_watters]

Sorry, just noticed this thread is 4 years old...locked.