Agents of Erosion

Agents of Erosion Goals The learner will be able to: Define weathering, erosion, and deposition. Name the four agents of erosion. Describe and explain how the agents of erosion cause weathering, erosion, and deposition Start

Weathering Erosion Deposition Continue

Weathering • Definition • Process by which rock materials are broken down by the actions of physical or chemical processes. • Example • Watch this explanation of Weathering Continue

Erosion • Definition • Process by which wind, water, ice, or gravity transport soil and sediment from one location to another. • Example • Watch this explanation of Erosion Continue

Deposition • Definition • The act or process of being deposited • Example • Watch this explanation of Deposition Continue

Four Agents Wind Glaciers (Ice) Waves Gravity Exit

Wind and Weathering • Causes abrasion by blowing sand and silt against exposed rock wearing away the rock’s surface. Continue

Wind and Erosion Types of Erosion • SaltationThe skipping and bouncing movement of sand-sized particles in the direction the wind is blowing • DeflationThe removal of fine sediment • AbrasionThe grinding and wearing down of rock surfaces by other rock or sand particles Continue

Wind and Deposition • Types of Deposition • LoessThick deposits of windblown, fine-grained sediment; can be found far away from source • DunesThe mounds of wind-deposited sand; common in deserts and along shores of lakes and oceans • The Movement of DunesGenerally, move in direction of wind Continue

Waves and Weathering • Causes fallen rocks and pebbles to bump and scrape against each other rounding and smoothing surfaces. Continue

Waves and Erosion • Energy in waves is released when waves break causing rocks to break down • Coastal landforms created by wave erosion Wave-Cut Terraces Headlands Sea Caves Sea Arches Sea Stacks Cliffs Continue

Cliffs • formed when waves erode and undercut rock producing steep slopes Photo Attribution: Original Image: “Cliff near Portinatx” http://www.flickr.com/photos/mprinke/2210146936/sizes/m/in/photostream/ By: m.prinkle Released under an Attribution License:http://creativecommons.org/licenses/by-sa/2.0/deed.en Continue

Sea Stacks offshore columns rock once connected to mainland Photo Attribution: Original Image: “Lava columns and sea stacks” http://www.flickr.com/photos/benhusmann/4619654631/ By: Ben Hussman Released under an Attribution License: http://creativecommons.org/licenses/by/2.0/deed.en Continue

Sea Arches • formed by continued erosion of a sea cave by wave action Photo Attribution: Original Image: “sea arch” http://www.flickr.com/photos/posk/5004820236/sizes/m/in/photostream/ By: Art Poskanzer Released under an Attribution License: http://creativecommons.org/licenses/by/2.0/deed.en Continue

Sea Caves formed waves cut large holes into fractured or weak rock along cliff base Photo Attribution: Original Image: “Cave in Progress” http://www.flickr.com/photos/rdrcollection/2129639590/sizes/m/in/photostream/ By: Rodney Ramsey Released under an Attribution License: http://creativecommons.org/licenses/by/2.0/ Continue

Headlands • finger-shaped projections form hard-rock cliffs erode slower than surrounding rock Photo Attribution: Original Image: “Harmony Headlands State Park, California. 13 Dec. 2008.” http://www.flickr.com/photos/mikebaird/3105703639/sizes/m/in/photostream/ By: Mike Baird Released under an Attribution License: http://creativecommons.org/licenses/by/2.0/ Continue

Wave-Cut Terraces • formed by worn back sea cliff, nearly level platform beneath water Photo Attribution: Original Image: “Wave-cut platform at Penrhyn Nefyn.” http://search.creativecommons.org/?q=wave%20cut%20terrace# By: Eric Jones Released under an Attribution License: http://search.creativecommons.org/?q=wave%20cut%20terrace# Continue

Waves and Deposition On-shore Deposits Waves carry materials such as sand, rock fragments, dead coral, and shells. These materials are deposited on a shoreline forming a beach Photo Attribution: Original Image: “Beach erosion.” http://www.flickr.com/photos/pagedooley/3777170527/sizes/m/in/photostream/ By: Kevin Dooley Released under an Attribution License: http://creativecommons.org/licenses/by/2.0/ Continue Off-shore Deposits Waves carry materials such as sand, rock fragments, dead coral, and shells. These materials are deposited on a shoreline forming a beach Photo Attribution: Original Image: “Settling on the Coast.” http://www.flickr.com/photos/gsfc/5204566057/sizes/m/in/photostream/ By: NASA Released under an Attribution License: http://creativecommons.org/licenses/by/2.0/

Gravity and Weathering • Causes abrasion to occur when rocks fall on one another wearing away at the rock surfaces Continue

Gravity: Erosion & Deposition • Works as an agent of erosion by influencing movement of water, ice, and causing both rocks and soil to move downslope • Mass movement:Movement of a section of land down a slope Rapid Mass Movement Slow Mass Movement Continue

Rapid Mass Movement Continue

Slow Mass Movement • Occur a little at a time yet more frequently resulting in more material moved collectively over time. CreepSlow downhill movement of weathered rock material Bent tree trunks evidence that creep is happening Continue

Glaciers and Weathering • Causes weathering by ice wedging and frost action; water freezes, expands, and cracks rock Continue

Glaciers and Erosion • Carve out large amounts of rock material altering the landscape and creating landforms. Landforms Horns Cirques Hanging Valleys Aretes U-shaped Valleys Continue

Horns Sharp, pyramid-shaped peaks that form when three or more cirque glaciers erode a mountain Continue

Cirques Bowl-shaped depressions where glacial ice cuts back into the mountain walls Continue

Aretes Jagged ridges that form between two or more cirques cutting into the same mountain Continue

U-Shaped Valleys Formed when a glacier erodes a river valley from its original V shape to a U shape Continue

Hanging Valleys Similar to glacial valleys that join the deeper main valley; can form waterfalls after the ice is gone Continue

Agents of Erosion