Streams and rivers drain carrying sediment in a watershed or catchment basin.
Deltas begin to form when it carries too much sediment and clogs the entrance into the basin.
At this point, the stream loses energy because of the increased sediment deposits. This forces the basin entrance to widen forming a delta.
Deltas take different shapes. If you have too much sediment deposits, a feature like a bird-foot delta forms. Let’s review the anatomy of how river deltas form.
Deltas are fertile and often overcrowded
When area flood, sediments spread across the region. When water recedes, soils are rich and fertile for agriculture purposes.
In this diagram, the river enters a lake. The water flow decelerates with sediments dropping in. A delta forms depositing a prism of sediments that gradually tapers out toward the lake interior.
Throughout geologic time, deltas deposit layers upon layers of sediment. For example, the diagram below depicts a vertical cross section through geological layers deposited by rivers, deltas and lakes.
Deposits from a series of successive deltas build out increasingly high in elevation as they migrate toward the center of the basin.
Don’t stop here.
Today, you’ve learned how river deltas form and how they are a common feature into basins. But you don’t have to stop here. If you want to expand your knowledge of Earth Science, then we have a river of information for you.
We’ve hand-selected articles on fresh water that may interest you below. Check ’em out:
Water is in the ground, on the surface, in the air and in our bodies. Streams, wetlands and swamps account for just 0.001% of the global water distribution. How much more is in our oceans, glaciers and groundwater? Find out where 326 million trillion gallons of water is on Earth.
When it rains, water zig-zags all the way through a tributary system to a river or lake. Watersheds are like upside-down umbrellas that catches all rain water. We all live in watershed.
2 theories exist for the origin of water on Earth: Did comets transport water? Or was there degassing from volcanoes from rocks existing within the crust? Water is what makes Earth unique. It’s the only planet that has it.