Chapter 11 Section 2 Stream and River Deposits

Chapter 11 Section 2 Stream and River Deposits Bellringer Even though flooding along rivers is potentially harmful, many farms are located near rivers. Why do people build farms along rivers? Record your answers in your science journal. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Objectives • Describe the four different types of stream deposits. • Describe how the deposition of sediment affects the land. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Deposition • After rivers erode rock and soil, they drop, or deposit, their load downstream. • Deposition is the process in which material is laid down or dropped. • Rock and soil deposited by streams are called sediment. • Rivers and streams deposit sediment where the speed of the water current decreases. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Deposition in Water • Placer Deposits Heavy minerals are sometimes deposited at places in a river where the current slows down. This kind of sediment is called a placer deposit. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Deposition in Water • A river’s current slows when a river empties into a large body of water, such as a lake or an ocean. • As its current slows, a river often deposits load in a fan-shaped pattern called a delta. • A delta usually forms on a flat surface and is made mostly of mud. These mud deposits form new land cause the coastline to grow. The world’s deltas are home to a rich diversity of plant and animal life. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Deposition on Land • When a fast-moving mountain stream flows onto a flat plain, the stream slows down very quickly. • As the stream slows down, it deposits sediment. • The sediment forms an alluvial fan. • Unlike deltas, alluvial fans, form on dry land. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Deposition on Land • The area along a river that forms from sediment deposited when a river overflows its banks is called a floodplain. • Flood plains are rich farming areas because periodic flooding brings new soil to the land. • Floods can damage property and cause a loss of lives. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Deposition on Land • A dam is a barrier that can redirect the flow of water. A dam can prevent flooding in one area and create an artificial lake in another area. • A levee is the buildup of sediment deposited along the channel of a river. This buildup helps keep the river inside its banks. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 11 Section 2 Stream and River Deposits Section Summary • Sediment forms several types of deposits. • Sediments deposited where a river’s current slows are called placer deposits. • A delta is a fan-shaped deposit of sediment where a river meets a large body of water. • Alluvial fans can form when a river deposits sediment on land. • Flooding brings rich soil to farmland but can also lead to property damage and death. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.