Not always. They can form at the mouths of any size stream or river.
The keys are velocity change and the amount of load the stream is carrying. When a river flows into another body of water and has a drop in its velocity, it can no longer carry as much sediment. Sediment begins to drop out and settles on the bottom. Large rivers, especially muddy ones, carry a large load of sediment and the deltas or alluvial fans they create are much more visible. The Mississippi is one of the best examples. But much smaller streams also develop alluvial fans. Its all a matter of scale and perspective.
2006-11-02 10:05:21
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answer #1
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answered by Tom-PG 4
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They are not, deltas are found at the mouths of any rivers that do not have excessive water energy to remove sediments and redeposit them elsewhere. Large rivers can carry large amounts of sediments, and their deltas can seem to be large in contrast. If you look at the Columbia River (which is a large river) you find that its delta is small, due to excessive energy of the California Current.
2006-11-03 06:46:12
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answer #2
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answered by Amphibolite 7
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Well that is not completely true. People only name the really large deltas (nile delta, mississippi delta, orinoco delta). A delta, as one poster mentioned occurs any place water, carrying sediment, is forced to slow down (causing it to dump it's sediment). this happens most consistently and in the largest quantities where large rivers run into the ocean.
Note also that there are a great many other factors. usually river deltas that are named are the big ones that have grown quite large, and this can only occur in places where there are not alot of other destructive forces to destroy the delta (like large waves), so you dont see many "delta's" in places like western coast of the US (large waves and strong currents) or places like eastern australia (not much sediment and big waves).
2006-11-02 10:10:08
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answer #3
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answered by d 3
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cause this is where, where the river, slows down enough meeting a large body of water, so that it does not have sufficient velocity to keep the dirt in suspension.
2006-11-02 09:59:57
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answer #4
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answered by yehoshooa adam 3
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