TMJC 2025 JC1H2 C2 Lecture 11 part 2 Delta

2025 H2 Geography Lecture 11 part 2- Deltas

Deltas • Deltas are fan-shaped deposits formed from built-up layers of sediments deposited by a river where it enters a standing body of water like a lake or calm sea. The river may have to branch into smaller distributaries to carry the water to the sea.

How are they formed? • Minute Earth: How are deltas formed

How are delta’s formed

Types of delta

Types of Delta: River Dominated Delta • Also known as a bird foot delta • When the river brings down enormous amount of fine silt, deposition can occur in a still sea • Along with the edges of the distributaries for a very long distance offshore • E.g. Mississippi River Delta

Types of Delta: Wave dominated delta • Wave-dominated deltas are created and shaped by the movements of waves within the body of water in question. • The waves influence the shape and formation of the river delta by shaping the sedimentary deposits near the river;s mouth. • The waves move the deposits from the mouth opening towards the shore, preventing a bar from building up • Because of this, these delta types don't often have many distributary channels or veins, as the flow of the river into the larger body of water is not resisted. The waves also serve as a natural sifting and sorting mechanism because light fine grains are washed away in the waves, while heavy sediments are left behind.

Types of Delta: Tide dominated delta • Tide dominated deltas are somewhat similar to wave ones, as the movement of water in the delta helps to form the shape and type of river delta that is created, but the resulting shape is very different. In these cases, the rise and fall of the tide is what has the biggest impact. • Tidal deltas often have many distributaries, as well as dendritic structures due to the presence of sandbars and ridges under the water. • The changes in the tides can cause certain river branches to become filled or blocked by silt, resulting in the birth of a new distributary. • Because of this, these deltas have many veins and arms, as the constantly moving tide causes the delta to morph often.