River Delta: How It Forms

River Delta Schematic

River deltas form when streams and rivers carry too much sediment clogging the entrance into the basin.

Because increased sediment builds up, this forces the basin entrance to widen forming a delta.

Deltas take different shapes.

For example, if you have too much sediment deposits in excess, a feature like a bird-foot delta forms.

Let’s review the anatomy of how river deltas form.

Deltas are fertile and often overcrowded

River Delta

When an area floods, 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 and loses energy 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.

Multiple River Deltas

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:

  • Global Water Distribution: Sources of Fresh and Salt Water
    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.
  • Watersheds Are Like Upside-Down Umbrellas
    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.
  • Earth’s First Water: Comets vs Volcano Outgassing
    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.
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