Changing Earth's Surface: Weathering, Erosion, and Deposition

Table of Contents • Chapter Preview • 3.1 Changing Earth’s Surface • 3.2 Water Erosion • 3.3 Waves and Wind • 3.4 Glaciers

Chapter Preview Questions • 1. The process that breaks down rock and other substances at Earth’s surface is called • a. uniformitarianism. • b. weathering. • c. mountain building. • d. erosion.

Chapter Preview Questions • 2. What is the term for the mixture of rock particles, minerals, • decayed organic material, water, and air? • a. bedrock • b. humus • c. loam • d. soil

Chapter Preview Questions • 3. Which of the following is a cause of mechanical weathering? • a. abrasion • b. oxygen • c. acid rain • d. living organisms

Chapter Preview Questions • 4. Conservation plowing, crop rotation, and contour plowing are methods of promoting • a. soil loss. • b. soil conservation. • c. loss of fertility. • d. loss of topsoil.

Suppose that you fill a jar halfway with layers of gravel, sand, and soil. Then you fill the jar with water, cover it tightly, and shake for 5 seconds. What effect would shaking the jar have on the soil, sand, and gravel? What would happen to them after the shaking stops? Explain your answer. What are the forces of erosion and deposition that shape our landscape?

Latin Word Origins de- From, down, away Deflation, deposition

Latin Word Origins flare Blow Deflation

Latin Word Origins -mentum Movement The act of, the result of

Latin Word Origins positus Put Deposition

Latin Word Origins sedere Sit, settle Sediment

Apply It! Review the Latin words and meanings. Look at the word sedere and the second meaning of mentum. Predict the meaning of sediment. Revise your definition as you read the chapter. Sample: Sedere means “settle” and mentum means “the result of.”

End of Chapter Preview

Section 1:Changing Earth’s Surface What processes wear down and build up Earth’s surface? What causes the different types of mass movement?

Wearing Down and Building Up • Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface.

Mass Movement • The different types of mass movement include landslides, mudflows, slump, and creep.

Mass Movement Activity • Click the Active Art button to open a browser window and access Active Art about mass movement.

End of Section:Changing Earth’s Surface

Section 2:Water Erosion What process is mainly responsible for shaping the surface of the land? What features are formed by water erosion and deposition? What factors affect a river’s ability to erode and carry sediment?

Sediment in Motion • Streams carry sediment in several ways.

Runoff and Erosion • Precipitation over the United States averages about 75 cm per year. About 22.5 cm becomes runoff. Generally, more runoff means more erosion.

Runoff and Erosion • Water flowing across the land runs together to form rills, gullies, and streams.

Erosion by Rivers • A waterfall forms where a flat layer of tough rock lies over a layer of softer rock that erodes easily. When the softer rock erodes, pieces of the harder rock above break off, creating the waterfall’s sharp drop.

Erosion by Rivers • Erosion often forms meanders and oxbow lakes where a river winds across its floodplain.

Deposits by Rivers • Deposition creates landforms such as alluvial fans and deltas.

The Course of a River • The slope and size of a river, as well as the sediment it carries, determine how a river shapes the land.

Erosion and Sediment Load • A river’s slope is usually greatest near the river’s source. As a river approaches its mouth, its slope lessens.

Sediment on the Move • The speed, or velocity, of a stream affects the size of the sediment particles the stream can carry. Study the graph, then answer the following questions.

Stream velocity Reading Graphs: What variable is shown on the x-axis of the graph? Sediment on the Move

Diameter of sediment particles Reading Graphs: What variable is shown on the y-axis of the graph? Sediment on the Move

About 50 cm/sec; about 90 cm/sec; about 800 cm/sec Interpreting Data: What is the speed at which a stream can move coarse sand? Small pebbles? Large boulders? Sediment on the Move

Small boulders Predicting: A stream’s speed increases to about 600 cm per second during a flood. What are the largest particles the stream can move? Sediment on the Move

The faster the speed of the flowing water, the larger the particles the stream is able to move. Developing Hypotheses: Write a hypothesis that states the relationship between the speed of a stream and the size of sediment particles it can move. Sediment on the Move

Erosion and Sediment Load • A river erodes sediment from its banks on the outside curve and deposits sediment on the inside curve.

More on Floods • Click the Planet Diary button for an activity about floods.

End of Section:Water Erosion

Section 3:Waves and Wind What gives waves their energy? How do waves shape a coast? What are the causes and effects of wind erosion?

Erosion by Waves • Waves shape the coast through erosion by breaking down rock and transporting sand and other sediment.

Erosion by Waves • Erosion and deposition create a variety of features along a coast.

Deposits by Waves • Waves shape a coast when they deposit sediment, forming coastal features such as beaches, spits, and barrier beaches.

How Wind Causes Erosion • Wind erosion moves sediment particles of different sizes in the three ways shown below.

Wind Deposition • Wind erosion and deposition may form sand dunes and loess deposits.

Links on Waves • Click the SciLinks button for links on waves.

Waves • Click the Video button to watch a movie about waves.

End of Section:Waves and Wind

Changing Earth's Surface: Weathering, Erosion, and Deposition

Changing Earth's Surface: Weathering, Erosion, and Deposition

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Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents

Table of Contents