Download Unit 1, Lesson 4 – Erosion and Deposition by Wind, Ice, and Gravity

Module E: Unit 1, Lesson 4 – Erosion and Deposition by Wind, Ice, and Gravity
How can wind shape Earth?
• When wind moves soil, sand, and rock particles, it acts as an agent of erosion.
• The grinding and wearing down of rock surfaces by other rock or sand particles is
abrasion.
• Rocks can become smooth and polished from abrasion.
• The removal of fine sediment by wind is called deflation.
• Desert pavement results when wind carries soil and fine sediment away from an
area, leaving only pebbles and small rocks behind.
• Dunes are mounds of wind-deposited sand, common in deserts and along the
shores of lakes and oceans.
• Dunes usually move in the same direction the wind is blowing.
• A dune’s gently sloped side usually faces the wind, which moves material up this
slope. Sand moves over the crest and slides down the steep face.
• Loess consists of thick deposits of windblown, fine-grained sediment.
• Loess deposits can be found far from their original source and can build up over
thousands or millions of years.
• Loess forms good soils for growing crops.
What kinds of ice shape Earth?
• A glacier is a large mass of moving ice that forms by the compacting of snow by
natural forces.
• Glaciers move downhill by gravity and cause erosion. As a glacier melts, it
deposits the materials it carries.
• Glacial drift is the general term for all materials carried and deposited by a
glacier.
• An alpine glacier is a glacier that forms in a mountainous area.
• As a glacier flows down a mountain, it can erode a V-shaped valley caused by a
stream into a U-shaped glacial valley.
• An alpine glacier can carve out bowl-shaped depressions called cirques, at the
head of a valley.
• A sharp ridge called an arête forms between two cirques that are next to each
other.
• When three or more arêtes join, they form a sharp peak called a horn.
• Continental glaciers are thick sheets of ice that may spread over large areas,
including across entire continents.
• Continental glaciers flatten and smooth the landscape.
• Erratics and kettle lakes are landforms produced by continental glaciers.
Melting the Ice
• During the last Ice Age, an ice dam held back the water of Glacial Lake Missoula.
• The dam broke and emptied the entire lake within 48 hours, forming huge
waterfalls, deep canyons, and tall ripple marks in the land.
• Lake Missoula reformed and flooded about 40 more times.
How can gravity shape Earth?
• Gravity influences the movement of water and ice. Gravity also moves rocks and
soil downslope.
• Mass movement is this shifting of materials due to gravity.
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Creep is the extremely slow movement of material downslope.
Rapid mass movements usually happen on steep slopes and are the most
destructive.
A rockfall happens when loose rocks fall down a steep slope.
A landslide is the sudden and rapid movement of a large amount of material
downslope.
A mudflow is a rapid movement of a large mass of mud.
Mudflows happen when a large amount of water mixes with soil and rock.
Deforestation, volcanic eruptions, and heavy rains can all create mudflows.