World Geo 3200/3202 October 2010

Introduction In this lesson you will: Explain how deltas are formed. (k) Contrast the terms arcuate delta, digitate delta, and estuarine delta. (k)

Deltas: Definiton Delta is a low lying area at mouth of river formed by deposition of silt deposition occurs because river slows as it enters ocean or lake.

How Deltas Form As a river is moving, it carries eroded material with it. The eroded material continues to flow downstream until it reaches still water if an ocean, sea, lake, or bay. When the river reaches the still water, the heavy particles are first to settle out. The lighter particles are carried further from shore. This process is then repeated farther out and a delta forms.

Types of Deltas Arcuate Digitate Estuarine

1. Arcuate Delta Curved in the shape of a bow. Fan shaped To the right is a satellite photo of the Nile Delta, notice the fan shape on the right-hand side of the mount of the river.

2. Digitate Delta Delta with long fingers of sediment reaching into the sea To the right is a satellite photo of the Mississippi Delta (p. 32), notice that it runs out into the Gulf of Mexico like a finger - unlike the Nile Delta.

3. Estuarine Delta Formed when rivers runs into a bay or estuary Created by sediment deposited from river outflow and from tidal inflow Tidal mud flats form and can be seen at low tide The Seine River Delta depicted in figure 2.12 on p. 32 of your book is a good example.

3. Estuarine Delta To the right is a satellite photo of the Amazon Delta, notice the tidal flats or islands that cover and uncover with the tide. This picture below shows a small estuarine delta in Notre Dame Bay.

Delta Review Read “Erosion and Deposition Process" on page of your text and complete the following: The term given to the low lying land at the mouth of a river. Silt is deposited there. The term given to a fan shaped delta. The name give to a finger shaped delta The name given to a delta that forms in a bay or estuary. Why does so much deposition occur at the delta of a river?

Delta Review The term given to the low lying land at the mouth of a river. Silt is deposited there. DELTA The term given to a fan shaped delta. ARCUATE The name give to a finger shaped delta DIGITATE The name given to a delta that forms in a bay or estuary. ESTUARINE Why does so much deposition occur at the delta of a river? THE FLOW RATE SLOWS BECAUSE THE WATER ENTERS A LAKE OR OCEAN> THE SLOWER MOVING WATER DROPS THE SILT