Download the printable Experiment Sheet here.
Deltas are landforms which form when rivers, carrying sediment, empty into larger bodies of water such as seas, oceans or other larger rivers. Deltas may also more rarely form where rivers emerge from mountains into dry interior basins, such as the Okivango Delta in Kenya. The landforms often form a triangular shape, after which the deposits are named (for the Latin upper case letter Delta, )
Deltas are important in the creation of new land along coastlines, helping reshape and replenish them with new sediment. The mixing of fresh river water and salty ocean water often creates unique ecosystems that support rich and diverse plant and animal life.
Deltas are further shaped by both onshore processes, such as the amount of sediment in water, and volume of water, and slope (speed/power) of the land over which the river courses, versus offshore processes, such as waves, tides and storms. All of these forces help shape the coastlines near rivers.
- Make a pile of sand on a table and dampen with water, to help the sand grains stick together.
- Pour water across the sttep upper slope of the pile of sand and let water run off onto the table.
- Observe sediment being picked up, or eroded from the pile and re-deposited by the water along the flat edges of the pile.
- Repeat the experiment, trying steeper or flatter sand slopes, more or less water, etc. and see how the landform changes.
Questions to consider:
- What shape does the deposit of sediment make? Why might it form that shape?
- Where/how would this happen in nature?
- Does caused the deposit grow over time? To become smaller?
- What other forces might cause the deposit to change shape along the coastline?
Example of A Delta: Ganges Delta, India
The Ganges River delta in India is the largest river delta in the world. The Ganges River drains the Himalaya Mountains to the north and is one of the largest rivers by volume in the world, second only to the Amazon and Congo Rivers. It ends its journey from the mountains in the Bay of Bengal and Indian Ocean, where it deposits the sediments of the Himalayas creating new lands.