Sunday, August 27, 2006
Freezing Lakes
Good morning,
Why do lakes not get frozen completely ?
Why is it that lakes freeze at the surface in winter to a certain thickness only and not completely ? In some places on earth the weather can be very very cold, yet the rivers and lakes would not be frozen right to their bottom !
Would we ever have a case when it does or it will happen ? The answer is that it will not happen, unless the world goes cuckoo, which it will not !
Imagine if ever the whole lake were to get frozen then what would become of all the living things therein; it would be one whole solid block of ice, a magnificent showpiece of preservation.
Nature has it way of preventing this. Water has a very unique characteristic, its anomalous behaviour. When water is at about four degrees Celsius, it is at it densest, that is, it is heaviest relative to the same volume; and being heaviest, that part of the water will sink towards the bottom. As it sinks it gets warmer in contact with the warmer water or the lake bottom. It will thus rise, and this circulation goes on continuously. So, while the water at or near the surface of the lake will eventually be cooled to zero degrees and get frozen, that at the lower part or at the bottom will not get frozen. Also, once the layer of ice is formed at the surface, it acts as a barrier against the lake getting colder; so there is no chance of the whole lake getting frozen.
Of course a very very shallow pond can get completely frozen. And theoretically, the whole lake can get frozen if the whole lake is cooled to zero degrees !
Now, why is water densest at four degrees Celsius, and not at zero degrees, since zero degrees is colder than four degrees ? Or why does ice being at zero degrees float in water which is above zero degrees ?
Scientists can explain how water becomes densest at four degrees, and frozen water which is ice, floats, but only God has the reason and the answer to the why of all these !
Have a nice day
Ronald
Why do lakes not get frozen completely ?
Why is it that lakes freeze at the surface in winter to a certain thickness only and not completely ? In some places on earth the weather can be very very cold, yet the rivers and lakes would not be frozen right to their bottom !
Would we ever have a case when it does or it will happen ? The answer is that it will not happen, unless the world goes cuckoo, which it will not !
Imagine if ever the whole lake were to get frozen then what would become of all the living things therein; it would be one whole solid block of ice, a magnificent showpiece of preservation.
Nature has it way of preventing this. Water has a very unique characteristic, its anomalous behaviour. When water is at about four degrees Celsius, it is at it densest, that is, it is heaviest relative to the same volume; and being heaviest, that part of the water will sink towards the bottom. As it sinks it gets warmer in contact with the warmer water or the lake bottom. It will thus rise, and this circulation goes on continuously. So, while the water at or near the surface of the lake will eventually be cooled to zero degrees and get frozen, that at the lower part or at the bottom will not get frozen. Also, once the layer of ice is formed at the surface, it acts as a barrier against the lake getting colder; so there is no chance of the whole lake getting frozen.
Of course a very very shallow pond can get completely frozen. And theoretically, the whole lake can get frozen if the whole lake is cooled to zero degrees !
Now, why is water densest at four degrees Celsius, and not at zero degrees, since zero degrees is colder than four degrees ? Or why does ice being at zero degrees float in water which is above zero degrees ?
Scientists can explain how water becomes densest at four degrees, and frozen water which is ice, floats, but only God has the reason and the answer to the why of all these !
Have a nice day
Ronald
# posted by chunmu @ 8:39 PM 
