Agents of Erosion
Erosion
• The process by which water, ice, wind or gravity moves fragments of rock and soil.
Water Erosion
• Rivers, streams, and runoff
Ice Erosion
• Glaciers
Wind Erosion
Mass Movements
• Landslides, mudslides, slump and creep
landslide clip.mpeg
Shoreline Erosion
• Erosion- the removal and transport of material by wind, water or ice
• Weathering- the breakdown of rock into smaller and smaller pieces by mechanical or chemical means
• Deposition- materials are dropped
Shoreline
• Shoreline- where land and a body of water meet.
• Deposition- materials are dropped– Waves are powerful agents of erosion and
deposition
Waves
• Wind moves over the ocean= waves– The size of the wave depends on the size of the wind– Waves may travel many kilometers
Waves don’t travel alone– They travel in groups called wave trains– Breaking waves are known as surf– The wave period is the time interval between breaking
waves
Pounding Surf
• Energy is released when waves break
• A wave can break rock or throw broken rock
•Waves wash into cracks of rock and break off boulders (huge rocks) or sand.
•New beaches can form!
Wave Deposits
• Waves can carry materials, including sand, rock fragments, and shells.
• Beach- any area of the shoreline made up of material deposited by waves– Not all beaches are the same
Compare the beaches…
• Beaches are made of different types of material deposited by waves.
Compare the beaches…
Hawaii- eroded lava Pieces of seashell
Stormy seas= pebbles and larger rocks
Wave Angles
• The way sand moves depends on the angle of the waves on the shore
• Waves come to shore at an angle
• Waves normally leave in an angle perpendicular to the shore
• Longshore current- water near and parallel to the shoreline
Wave AnglesSand Movement
Longshore Current
Wave Direction
Wave Angles- Diagram
Offshore Deposits
• Waves erode material from the shoreline and transports and deposits it– Landforms are created in open water
Wave Erosion
• Waves strike (hit) and erode rock and wear away soil and rock
– How quickly sea cliffs erode depends on the hardness of the rock and the energy of waves
Wind Erosion
Has wind ever blown your papers?
• You already know how wind erosion works!
Take cover!
• Loose rock material
• Deserts
• Coastlines
– Plants– Plant roots anchor (keep down) sand and soil
Wind Erosion
• Wind moves material in different ways
• Material is moved by saltation
• Saltation is the movement of sand-sized particles by skipping and bouncing in the direction of the wind
SaltationParticles roll forward or bounce in the air.
Deflation
• Deflation is the lifting and removal of sediment by wind
Deflation
Deflation
Deflation
Before After
Deflation hollows
Abrasion• Abrasion is the grinding and wearing down of
rock surfaces by other rock or sand– Strong winds– Loose sand– Soft rocks
Wind Deposited Material
• All material carried by the wind is eventually deposited
– Dunes (common in deserts and along shores)– Loess
Loess is finer than sand. It feels like powder.
Glacier
• Glacier- mass of moving ice
• 2 types– Alpine– Continental Glacier
Glacier
• Form in areas of snow on ground all year– High elevations– Polar regions
Glacier
• Snow piles up snow packs crystals• Giant ice mass• “Rivers of Ice”- begin to move (gravity)
Alpine Glaciers• Forms in mountainous areas
Valley Glacier- form in valleys with streams flowing downhill
Forms a U- shape
Continental Glacier
• Not all glaciers are “rivers of ice”
• Can spread across entire continents
• Continental glaciers- continuous masses of ice
Continental Glacier
• Continental ice sheet- largest type of glacier*– Antarctica is almost completely covered by an ice
sheet – Contains 91% of glacial ice on planet– ½ times the size of United States– It is 4,000 m thick in some places; covers
everything except highest mountain peaks
Ice Shelves
• Ice shelf- an area where ice is attached to the ice sheet but resting on open water
• Ross Ice Shelf- largest ice shelf– Attached to ice sheet covering Antarctica
Ross Shelf
Ross Shelf
Icebergs
• Large pieces of ice that break off an ice shelf
Icebergs • Large pieces of ice that break off an ice
shelf
• Icebergs form by calving
The Titanic• Most of an iceberg is below the surface
– Hazard for ships
