How are river delta's formed???

Answer 1

A delta is defnies as "a deposit partly subaerial built by a river into or against a body of permanent water. The outer and lower parts are necessarily constructed below water level, but its upper and inner surface must be land maintained . . . by a river . . . therefore consists of a combination of terrestrial and marine, or at least lacustrine strata."

So sediment transport by a RIVER is key to having a delta.

River processes: sedimentation at the mouth of a river where flow runs into standing sea (or lake) water. Get rapid decrease in shear stress (along with flow expansion at mouth of channel, forcing deposition = distributary mouth bar.
In a model described by Coleman, the velocity reduction at the river mouth is not uniform across the region of flow expansion. Thus, sedimentation rates on the bar are not exactly equal. If one area gets a bit higher sedimentation than an ancient area, you can develop a bar that has topography, essentially the mouth bar consists of local highs and lows that causes the flow to split around the highs. This is much like in a braided stream where local areas of flow expansion lead to bar deposition and flow splitting. In the case of delta river mouths this eventually causes the river to split into two, or more, paths. As the river progrades seaward, and the bar builds up above sea level, we find a river pattern on the delta plain (the river dominated, above sea level part of the delta) that is a distributary pattern.

Delta Front: The zone just seaward of the river mouth is where the distributary mouth bar is deposited, and represents the area where the coarsest (usually sandiest) marine sediments are found. This area can be reworked by waves etc., but in general the area just seaward of the shoreline on a delta is called the delta front

the area farther seaward of the delta front is a zone where the fine grained, silt to clay, material carried in by the river is deposited. In this zone sedimentation rates of fine grained material are higher than found farther off on the shelf. These muddy build ups are referred to as the Prodelta zone.

Answer 2

A river picks up soil as it flows toward the sea.
When the water flows into a wider area (a wide spot in the river or into the ocean) the velocity is reduced and the soil load settles out thus forming sand bars in the river and deltas it the ocean.
The sand bars and deltas are constantly changing shape as the velocity and volume of flowing water rises and falls.

Answer 3

As a river flows to the sea, it will pick up particulate matter from the river bed, and the velocity of the river flow will carry it to the sea.

As the river enters the sea, the velocity of the flow essentially decreases to zero, and the particulate in the river water will succomb to gravity and accumulate at the mouth of the river. Over time, this particulate will build up, and force the river to flow around it. This is repeated millions of times over millions of years, until the triangular delta is formed.

Answer 4

At the river mouth, the river deposits alluvium. over time, a flat piece of land made up of layers of alluvium is formed at the river mouth. this is known as delta. the river may branch into smaller channels called distributaries as it crosses delta. this is because the main channel of the river is often blocked by the depostits of alluvium. the river is therefore forced to divede into smaller channels. a delta is formed when : -the river carries much materials - the sea at the river mouth is shallow - the currents and waves around the river mouth are weak hope it helps.............

Answer 5

As the river water enters the ocean or lake, it slows down and any sediment (minerals, soil, etc.) being carried will fall out of the water.

Answer 6

erosion