Unit 7 Lesson 3 Weathering, Erosion, and Deposition Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 7 Lesson 3 Weathering, Erosion, and Deposition

Copyright © Houghton Mifflin Harcourt Publishing Company

Crushers!


What is weathering?

• Weathering is this process by which rock breaks down into smaller pieces or changes composition.

• Weathered rock pieces, known as sediment, are an important component of soil.

• Differential weathering describes how different rocks in the same environment can weather at different rates.


What is weathering?

• Physical weathering is the breakdown of rock into smaller pieces. Physical weathering does not change the chemical makeup of a rock.

• Chemical weathering changes the chemical makeup of a rock.

• Physical weathering and chemical weathering often work together in nature.



What causes physical weathering?

• Abrasion is a process where agents, such as wind, water, and ice, carry particles that scrape against rock.

• Plant roots can grow into the cracks of a rock and break the rock into pieces. Water accomplishes a similar feat by seeping into cracks, freezing, and expanding.

• Digging animals can expose buried rocks to agents of physical weathering.



What causes chemical weathering?

• Two main agents that cause chemical weathering are oxygen and acids.

• Oxidation occurs when certain chemicals in a rock react with oxygen to form new chemical compounds.

• Acid precipitation can speed up chemical weathering.

• Microscopic organisms, lichens, and mosses can also cause chemical weathering.



Earth Movers


What are erosion and deposition?

• Erosion transports rock, sediment, and soil from one place to another.

• Deposition lays down rock, sediment, and soil.

• Erosion and deposition work together, constantly reshaping Earth’s surface.


What causes erosion and deposition?

• Wind, water, ice, and gravity are agents of both erosion and deposition.

• Flowing water moves millions of tons of sediment every day.

• A glacier is a large mass of ice that exists year-round and flows slowly over land.

• Alpine glaciers can erode land to form jagged ridges and peaks. Continental glaciers can leave depressions in the land in which lakes form.



What causes erosion and deposition?

• Wind can move soil and sediment. Wind erosion and deposition creates sand dunes.

• Gravity causes rocks and soil to move down a slope, a process known as mass movement.

• Gravity also determines the movement of other agents of erosion, such as water and ice.



Shore Shapers


How can weathering and erosion shape coastal features?• Ocean waves and currents play a large role in

shaping Earth’s shoreline.

• Weathering and erosion along a shoreline can form sea cliffs, wave-cut platforms, sea caves, sea arches, and sea stacks.

• Some parts of a shoreline may erode faster than others, leaving behind headlands.


How can deposition shape coastal features?• Waves and currents deposit material to form

features, and beaches are the main features of coastal deposition.

• Longshore currents can deposit materials offshore to create features such as sand spits, tombolos, and barrier islands.



Drip, Drop


How can flowing water shape land?

• Weathering and erosion by flowing water form various land features, such as valleys, cliffs, and canyons.

• Acids in groundwater can slowly dissolve rock to form caves.


How can flowing water shape land?

• Deposition by flowing water forms features such as alluvial fans, deltas, and floodplains.

• Cycles of flooding cause layers to build up along rivers, forming a flat floodplain.

• Groundwater can deposit dissolved minerals in new locations to form stalactites and stalagmites.



Ice Sculptures


How can glaciers weather and erode Earth’s surface?• As glaciers move, they pick up material and

scrape out the land beneath them.

• Several land features characteristic of glacial weathering and erosion are cirques, glacial horns, and arêtes.


What can melting glaciers deposit?

• Glaciers also shape Earth’s surface by leaving behind lakes and deposits of rock and sediment.

• Glacial deposition can create land features, such as glacial till, moraines, drumlins, erratics, and kettle lakes.



Documents

Unit 7 Lesson 3 Weathering, Erosion, and Deposition Copyright © Houghton Mifflin Harcourt Publishing Company