Deltas are depositional landforms found at the mouth of a river where the river meets a body of water with a lower velocity than the river (e.g. a lake or the sea). For a delta to develop, the body of water needs to be relatively quiet with a low tidal range so that deposited sediment isn’t washed away and has time to accumulate.
17 – Delta environments
Delta Formation in a Stream Table
Delta Depositional Environments & Stratigraphy | GEO GIRL
Frequently Asked Questions
What causes delta landform?
A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment.
Why is sediment deposited in a delta?
The sediment is dropped at the mouth of the river. Some rivers drop so much sediment that waves and tides can't carry it all away. It builds up in layers forming a delta. Some deltas are so large that people can live on them.
What is created by deposition in a delta?
Deltas are landforms formed at the mouth of a river, where the river meets a body of water with a lower velocity than the river (e.g. a lake or sea), resulting in the reduction in the river's capacity to transport sediment.
How are deltas formed in coastal areas?
River deltas are formed when the supply of sediments to the coast by a river is faster than they are dispersed by waves, tides and the associated currents. They are the result of depositional and erosional processes under the influence of currents, waves and tides.
Where are depositional deltas in the Indian plains?
Such fans appear throughout the Himalayan foothills in the north Indian plains. These are narrow ridges of low height on both sides of a river, formed due to deposition action of the stream, appearing as natural embankments.
How are depositional facies in deltaic environments formed?
Deltaic depositional facies result from interacting dynamics processes (wave energy, tidal regime, currents, climate, etc.), which modify and disperse riverborne (fluvial) clastic deposits.
When does a fluvial depositional land form a Delta?
This type of delta emerges when limestone sediment deposits do not allow downward seepage of water. The distributaries seem to be flowing over projections of these deposits which appear as a bird’s foot. The currents and tides are weak in such areas and the number of distributaries lesser as compared to an arcuate delta.
How are deltas formed in a large river?
A build up of alluvium on the banks of a river can create levees, which raise the river bank. Deltas are found at the mouth of large rivers - for example, the Mississippi. A delta is formed when the river deposits its material faster than the sea can remove it. There are three main types of delta, named after the shape they create.