|MadSci Network: Evolution|
Rose: You have asked a very good question. I will say right away that I don't believe anyone knows the answer. However, we can make some educated guesses. The primordial ocean probably differed from the modern ocean in a lot of ways. It wasn't as salty. The salt in the ocean comes from minerals, and it took some considerable amount of time for enough minerals to dissolve to make the ocean as salty as it is today. The modern ocean has a lot of floating organisms, many of which are large enough to see, and many of which have white calcium-carbonate shells. None of this would have existed in the primordial ocean. The modern ocean contains, near the mouths of rivers, a fair amount of suspended sediment. Four billion years ago the kinds of sediment reaching the ocean would have been very different. Erosion was much faster, because there were no plants to trap sediment. However, weathering was probably slower, because plants and microorganisms cause a lot of weathering. Therefore, most of the sediment reaching the sea would have been relatively coarse, and it would have settled to the sea floor relatively quickly. Of course, the sea would not have been polluted by people; there was no floating tar (no tar at all; it comes, ultimately, from decaying organisms), no bubbles of detergent, and no bits of plastic, paper, or wood. I think that the primordial ocean was clearer than the modern ocean. If there were places where the primitive organic molecules were concentrated, such as in coastal lagoons, the water may have been cloudy, but not as cloudy as it is today in similar places. Aside from greater clarity, the color may not have been much different from what it is today in the open ocean. David Kopaska-Merkel Geological Survey of Alabama PO Box 869999 Tuscaloosa AL 35486-6999 (205) 349-2852 FAX (205) 349-2861 www.gsa.state.al.us
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