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Forces That Shape Earth’s Surface. Weathering. Weathering is the breaking down of the materials of Earth’s crust into smaller pieces. There are two types of weathering: 1. Physical weathering 2. Chemical weathering.
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Weathering • Weathering is the breaking down of the materials of Earth’s crust into smaller pieces. • There are two types of weathering: 1. Physical weathering 2. Chemical weathering
Physical weathering – is the processes that mechanically break up rocks into fragments, such as the movement of water, wind and ice, and frost action. Physical weathering is also known as mechanical weathering.
Chemical weathering – is the breaking down of the materials in rock through chemical alteration of those minerals. Chemical weathering involves reactions between air and water and minerals in rocks. An example of chemical weathering occurs when certain metallic elements combine with oxygen to form oxides. This is known as oxidation. The most familiar oxidation form is the “rusting” of iron in rocks or soil that produces a reddish brown stain of iron oxide.
Erosion • Erosion is the carrying away of pieces of weathered rock by gravity, water, wind, and ice. Piece by piece erosion can carry away a bolder, a hill, or even a whole mountain range!
ErosionalForces: • Gravity • Glaciers • Wind • Water
Erosional Forces • These agents of erosion can only move material when they have enough energy to move the object. • Another thing they have in common is they will deposit, or drop, the material they carry when they have lost theenergy.
Gravity as a force: • Gravity is the force which Earth has on all objects. • It pulls boulders, soil and everything else to the lowest point possible. • When gravity moves materials downslope this is then called mass movement.
Erosion by slump • Slump - a type of mass movement that occurs when a mass of material moves down a curved slope.
Erosion by Creep • Creep is the slow movement of soil downslope that causes fence poles, telephone poles to tilt in the direction of movement.
Erosion by Rock Slides • Rock slides happen when layers of rock slip downslope suddenly. • Rock slides can be very fast and very dangerous • Very common in mountainous areas.
Erosion by Rockfalls • Rockfalls occurwhen material free falls through the air.
Glaciers as Agents of Erosion • A moving mass of ice and snow is called a glacier. • Glaciers form when snow and ice build up faster than they melt. • There are two types of glaciers: • Continental glaciers and • Valley glaciers
Continental Glaciers • Continental glaciers cover large parts of continents such as Antarctica.
Valley Glaciers • Valley glaciers are found in mountain regions all around the world. They begin at the top of the mountain where it is snows all year and the temperatures are always below freezing.
Glaciers • About 18,000 years ago glaciers covered 28% of the Earth’s surface. • Since that time they have been melting and now cover about 10% of the Earth. • Greenland and Antarctica are almost completely covered in ice.
Glacier Erosion • Glacial plucking is a process that occurs when moving glacier picks up loosened rock particles.
Wind Erosion • Wind is a very powerful force in erosion. • Through blowing away silt and clay by deflation or by eroding down rocks by abrasion.
Sandstorms Are strong winds that carry sand particles through the air.
Dust Storms A strong wind storm that fills the air with thick dust.
Windbreaks Hedge or fence of trees designed to lessen the force of the wind and reduce erosion
Roots Vegetation is planted to reduce soil erosion. Plants with fibrous root systems, such as grasses, work best at stopping wind erosion.
