When Rivers Run Into The Ocean
The place where a river enters a lake, larger river, or the ocean is called its mouth . As a river flows, it picks up sediment from the river bed, eroding This meeting of big and small fish means there is more for people to catch. Where rivers meet the ocean is called the mouth of the river. rivers, the Amazon deposits a lot of soil and sediment, forming a delta, as it enters the ocean. The confusion of swirling water and suspended sediments disorients But the mixing of freshwater streams and rivers with salty ocean tides in.
This kind of stratification is also observed in other coastal areas, such as in the Baltic Sea between Denmark and Sweden, and in the Norwegian fjords. In the case of the Mississippi River, however, the situation is exacerbated by the especially high levels of nutrients it contains.
The presence of the nutrients leads to profuse algal growth.
The Mississippi River and the Gulf of Mexico dead zone « World Ocean Review
When the algae die their remains sink into the lower water layer. There they are broken down by bacterial activity, a process that consumes oxygen. This causes the oxygen levels in the deep-lying saltwater layer to drop drastically. Free-swimming organisms flee the area due to the oxygen deficiency.
Less mobile animals such as mussels die. In an oxygen-deprived area of more than 20, square kilometres was observed.
11 Incredible Points In The World Where Major Bodies Of Water Join Together
This is equal to half the area of Germany. There is considerable evidence that the oxygen problem associated with stratification has only begun to occur more frequently since the middle of last century. The increase is probably due to the rising nutrient concentrations, especially nitrogen, which has trebled since the s. A popular US airline with questionable service except for those delicious little snacks they serve with your drinkoften-delayed flights, and a hilarious in-flight safety video.
A triangle-shaped deposit of sediment that forms where a river or stream flows into an ocean, lake, or other large, standing body of water.
Deltas are beautiful landforms, especially when viewed from above. Roughly triangular in shape, deltas are full of complex, wonderful detail: Composed of soft sediment and other alluviumdeltas are shapeshifters: Deltas form and evolve at the mercy of both river or stream and ocean or other large, standing body of water. They change with the seasons and with the years, based on waterflow and tides and weather and— in recent years— human influences, such as dams and levees. Deltas are almost chimera landforms: Despite the shapeshifting, many deltas remain in the same location— more-or-less— for millennia, building up thick, rich sediment deposits that are generally good places to live and grow food and which are also greatly valued by geologists trying to understand past climate conditions and ancient river-flow.
A delta in Bangaladesh.
Image courtesy of Peter Clift. Deltas form when faster-moving, channeled water in a river or stream meets a standing or still body of water such as an ocean or lake. Fast-moving waters are able to carry a significant amount of sediment with them as they travel. However, slower-moving waters carry less sediment, and in still waters most sediment will drop out, falling to the bottom of the body of water.
Certainly, even still bodies of water such as oceans and lakes contain some sediment. However, they are able to hold much less sediment than a fast or even slow moving river or stream.
When a river or stream enters a standing body of water, the water spreads out and the velocity of the water drops, along with the carrying capacity of that water for sediment.
The large amounts of sediment that drop out because of the velocity change form the soft delta. Often, deltas have a roughly triangular shape— hence the name.
The Greek historian Herodotus BC — BC noticed that the sediments deposited at the mouth of the Nile River in Egypt formed a roughly triangular shape, like the Greek letter delta. So, Herodotus starting calling the mouth of the Nile a delta .
However, not all deltas are triangular in shape.
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- The transition from salt to fresh water is turbulent, vulnerable, and incredibly bountiful
- The Mississippi River and the Gulf of Mexico dead zone
Many deltas are roughly triangular because rivers slow down and fan out— often branching into smaller streams amidst the delta sediments— when they reach a standing body of water.