When you study Geography, you will come to know that our Earth is huge, and the massive land on which we live is just ¼ of its total size. Three quarters of the Earth’s size is water, and the land on which we live is divided into a number of landforms that come into contact with it. Typical landforms are islands, sounds, rivers, shorelines and deltas. When we talk about a delta, it is a wetland that forms as a river empties its contents into another water body. If you are fascinated about the Geography of this Earth, then this oneHOWTO article will give you a deeper understanding of what is a delta in Geography.
Delta, the name
'Delta' is the fourth letter of Greek alphabet, and looks like a triangle in its shape. Deltas in Geography got their name from this Greek alphabet due to its physical shape and formation.
Formation of a delta
Deltas can be found in any place where a river enters into another water body. They are located in all parts of the world, except for the South and the North poles. Some of the most popular deltas are: Nile River Delta, Tiber River Delta, Sacramento River Delta and Seine River Delta among hundreds of others.
A delta forms when a river enter into an ocean or sea, due to which, deposits of clay, sand, silt and gravel are formed around the river’s mouth. The deposits build layers around the river’s mouth, creating a platform termed as alluvium. The waters then overflow these alluviums, and get divided into a number of branches known as distributaries. These distributaries create a delta which looks like a triangular fan or a tree with branches.
Parts of Delta
There are four distinct parts of a delta:
- Subaqueous: This part of a delta remains just below the mark of the low tide. It consists of very fine silt the size of which reduces as you move away from the river’s mouth.
- Subaerial: This part is situated above the mark of low tide. It mainly consists of rocks and sands in varying sizes. They constantly remain in the flux because of the tidal force actions.
- Upper plain: This is the point where the delta starts. Silt present here contains the largest of particles, and is minimally influenced by the forces of the larger water body.
- Lower plain: This is the point where the river flows into the other water body. The tidal forces as well as the river current influence the formations of silt deposits in this part.
Types of delta
Deltas are divided into four types, depending on what dominates them:
- Dominated by waves: This type of delta starts as a standard wave, and then gets dragged towards the fan’s outer edge. It usually gets a classic triangle shape due to its formation.
- Dominated by tides: This type of delta is completely covered by tides as they enter in. It usually has several branches that are followed through to the bigger water body.
- Gilbert delta: This kind of delta is formed when a river meets a freshwater lake. It has coarse silt due to the silt being thrust into the lake very quickly.
- Cuspate delta: This kind of delta is usually tooth shaped, and forms where the is tidal force in different directions. These types are rare and occur only on huge water bodies.
Importance of deltas for humankind
Deltas are abundant sources of ground water, which can be extensively used for agriculture. Common crops grown in deltas are rice, asparagus and other irrigating crops.
These wetlands are diverse ecosystems with immense ecological importance. They absorb runoff waters from storms and floods. They create friendly environment for the survival of a number of animals as well, including fish, oysters, insects, birds and others. Bears and tigers can also be part of a delta in Geography.
They filter water that is slowly entering the larger water body through a network of river distributaries. Due to this, the pollution elements flowing into the water body is minimized from the upstream. Deltas are significant wetland habitats as well, and are home to a number of plants and herbs, including worts, hibiscus and lilies.
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