Transitions in Water

Good, Lots of Facts Good facts, Well Presented

The Keys To Unlocking Transitions in Water

        When examining waters change from fresh to coarseness as well as from salt to

fresh one quickly finds the importance of estuaries. In terms of geology,

present-day estuaries argon young and ephemeral coastal features. Todays estuaries

began to take their current variant during the last interglacial period, when sea aim

rose about 120 m (Braun 36). However, the relatively high sea levels and extensive

estuaries found today have been mark of only about 10 to 20 percent of the

last gazillion years. When sea level was lower, during glaciation periods, estuaries

were much smaller than they are at present and were located on what is now the

continental slope. Unless sea level rises, estuaries tend to fill with sediments and

become much smaller. The sediments come from riverborne terrestrial materials

from the decay continents and from sand transported upstream by the tides from

the continental shelf (Braun 55).

                                                                       

        It is in estuaries that most of the worlds freshwater runoff encounters the

oceans. Because fresh water is lighter, or less dense, than salt water, unless the

two are miscellanyed by the tides or winds, the fresh water remains at the surface,

resulting in a salinity gradient.



Tides force seawater inland as a countercurrent

and produce a saltwater wedge below the freshwater surface waters (Bellamy

62).

        Estuaries are always in a state of change and hardly ever in a steady state.

The principal energy source are tides, cause estuarine mixing, but wind, wave

motions, and river runoff can also be important locally (Braun 45). Salt water and

fresh water mix to form brackish water. The three main estuarine

ones--saltwater, brackish, and freshwater--can shift seasonally and vary greatly

from one...

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