RE: Earth may have underground 'ocean' three times that on surface
June 13, 2014 at 11:02 am
(This post was last modified: June 13, 2014 at 11:18 am by Anomalocaris.)
Actually, this is old, and incomplete, news.
The upper bound of the total inventory of water in earth's mantle by modern estimate have long since gone way beyond 3 times the total volume in the ocean. 20-50 times is not unreasonable.
Most of the water in the earth is likely to be permenently sequested in the mantle and have never and would never come out. The question is how much of the water is in communication with the surface (ie the particular molecules are likely to reach the surface at least once during earth's life, certainly not all at once)
Also, the oceans have not remained the same size. Early in earth's history the total volume of water on the surface was much greater. Some estimate 50% greater. Water have been steadily consumed into the mantle at subduction zones since at least 2.5 billion years ago, and the consumed water has not returned to the surface through volcanos and other forms of outgassing at nearly the same rate as it is being consumed. So total inventory of surface water on earth has steadily decreased.
If plate tectonics does not stop, then the subduction process will likely consume all the oceans on the surface of the earth long before the sun goes red giant. When that happens, there will only be a small isolated lakes and oasis on the surface subsisting on the water vapor being outgassed from any ongoing volcanic activities, balanced by the loss of water vapor to space.
The upper bound of the total inventory of water in earth's mantle by modern estimate have long since gone way beyond 3 times the total volume in the ocean. 20-50 times is not unreasonable.
Most of the water in the earth is likely to be permenently sequested in the mantle and have never and would never come out. The question is how much of the water is in communication with the surface (ie the particular molecules are likely to reach the surface at least once during earth's life, certainly not all at once)
Also, the oceans have not remained the same size. Early in earth's history the total volume of water on the surface was much greater. Some estimate 50% greater. Water have been steadily consumed into the mantle at subduction zones since at least 2.5 billion years ago, and the consumed water has not returned to the surface through volcanos and other forms of outgassing at nearly the same rate as it is being consumed. So total inventory of surface water on earth has steadily decreased.
If plate tectonics does not stop, then the subduction process will likely consume all the oceans on the surface of the earth long before the sun goes red giant. When that happens, there will only be a small isolated lakes and oasis on the surface subsisting on the water vapor being outgassed from any ongoing volcanic activities, balanced by the loss of water vapor to space.
