Talk:Seafloor spreading
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[edit] Ocean growth
I think that the ocean in fact does not get bigger because of plate tectonics. If the magma spreads the plates apart and creates more oceanic crust, then the oceanic plates will just go below other plates and the ocean will get new crust and lose old crust. I do think, however, that the land masses will get bigger from the rifts on the land and the land plates will go over all the oceanic crusted plates. User:65.74.253.34
- Quite right - the rate of new crust formation at mid ocean ridges must be balanced by subduction otherwise the Earth would have to grow. The history of the formation of contintal crust is currently an area of active research. However, I think it is fair to say that, over the Earth's history, the area of the contintal crust has grown. For example, volcanic island arcs have formed in the ocean basins and moved towards subduction zones where they are accreted to the continent forming new continetal crust. User:Andreww
- Formation does not have to be balanced by subduction. For example, folding can shorten length, either of ocean material or by raising the Himalayas instead of quietly subducting India. Continental plates may get subducted rather than oceanic, thus more ocean. There are many factors, such as erosion filling the Gulf of Mexico. Also, perhaps "ocean getting bigger" is not correct if one uses Iceland as being part of spreading — there crust grew to the surface and although there is spreading it may make more land rather than making more oceanic crust. (SEWilco 09:56, 5 Apr 2005 (UTC))
- Correct, the ocean as a whole does not get bigger, but the pacific ocean is shrinking. This is because there are more subduction zones than ridges around the Pacfic plate. This is balanced by the atlantic ocean, which is growing as fast as the PAcific is shrinking. -Anonymous
The Earth can't get bigger due to subduction zones that destroy the older rock, so you are indeed correct that the ocean floor does not get bigger. It's almost like two steps forward and two steps back.
- I understand the prinicple of earth remianing the same size due to subduction, formation, etc. However, something has always baffled my mind. As with water, when it cools, and freezes, the volume of the water expands. Do the materials that earth is comprised of, follow a similar pattern? Because with the theory that earth is "cooling off" this would imply that the volume of earth will infact change over time. Emilyjane 22:25, 24 March 2006 (UTC)
- Water is unique in that there is no other known substance that expands when it solidifies, so the Earth wouldn't be expanding due to cooling. Every second the Earth is bombarded by billions of particles and meteorites, increasing the mass of the Earth. At the same time, the Earth loses gas molecules from the upper atmoshpere all the time. The percentage of Earth's total size that any of these changes represent is negligible, however.—WAvegetarian•CONTRIBUTIONSTALK• EMAIL• 05:49, 27 March 2006 (UTC)
I agree with a guy above me.Vinaq 19:57, 6 March 2007 (UTC)Vinaq
Yes, it maybe true on the part that it may be a cycle so the earth would not get bigger, however, it doesn't really answer the question given by Emilyjane. If that is so therefore in the future the ice that has been melted would not contribute to the volume of water in the earth? it is 70% water and only 30% of land mass, would that percentage increase? vahn_dinio 10:25, 15 May 2008
- Depends on many things. The ocean levels were recently over 100 feet lower, but it's hard for them to rise 100 feet above the current level because shallow seas on land so greatly expands the volume to be filled in order to rise. Ratio calculators then have to decide how much salt marsh is to be counted as ocean. The ratio hasn't changed recently because it takes a long time for continents to grow or shrink, and even a depleted ocean still fills the ocean basin once it falls off the continental shelf.. -- SEWilco (talk) 04:45, 14 May 2008 (UTC)
[edit] Cleanup
Is it just me, or is this hard to read? I think it needs cleanup, but I need approval before the stamp goes up. -Anonymous
