Erosion

Prepared by:Ida Lyn A. AzueloBSED- Physics 2

Earth Science

EROSION

Erosion is the act in which earth is worn

away, often by water, wind, or ice.

A similar process, weathering, breaks down or dissolves rock, weakening it or turning it into

tiny fragments.

Erosion is a natural process;

it is part of the constant recycling of Earth materials that is called the rock cycle.

»Water

»Wind

»Ice

The agents of erosion that wear away at the surface of the Earth:

Erosion by Water

Moving water is the major agent of erosion. Rain carries away bits of soil and slowly washes away rock fragments.

• Four primary types of erosion that occur as a direct result of rainfall:

1. Splash erosion - the impact of a falling raindrop creates a small crater in the soil, ejecting soil particles.

2. Sheet erosion - the transport of loosened soil particles by overland flow.

3. Rill erosion - refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes.

4. Gully erosion -  occurs when runoff water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow, removing soil to a considerable depth.

Rummu, Estonia

A spoil tip covered in rills and gullies in Rummu, Estonia

Erosion by Water

Rushing streams and rivers wear away their banks, creating larger and larger valleys.

Streams erode their banks in three different ways:

1) the hydraulic action of the water itself moves the sediments,

2) water acts to corrode sediments by removing ions and dissolving them, and

3) particles in the water strike bedrock and erode it.

The water of streams can erode in three different places:

1) lateral erosion erodes the sediment on the sides of the stream channel,

2) down cutting erodes the stream bed deeper, and

3) headward erosion erodes the channel upslope.

Erosion by water changes the shape of coastlines. Waves constantly crash against shores. They pound rocks into pebbles and reduce pebbles to sand. Water sometimes takes sand away from beaches. This moves the coastline farther inland.

Erosion by Water

Waves in oceans and other large bodies of water produce coastal erosion. The power of oceanic waves is awesome, large storm waves can produce 2000 pounds of pressure per square foot. The pure energy of waves along with the chemical content of the water is what erodes the rock of the coastline.

Erosion by Water

The battering of ocean waves also erodes seaside cliffs. It sometimes bores holes that form caves. When water breaks through the back of the cave, it creates an arch. The continual pounding of the waves can cause the top of the arch to fall, leaving nothing but rock columns. These are called sea stacks. All of these features make rocky beaches beautiful, but also dangerous.

Etretat

Paracas Sea Cliffs

White Cliffs of Dover

Látrabjarg

Bunda Cliffs

Cabo Girao

Acantilados de Los Gigantes

Fira

Kalaupapa Cliffs

Cliffs of Moher

The battering of ocean waves also erodes seaside cliffs. It sometimes bores holes that form caves. When water breaks through the back of the cave, it creates an arch. The continual pounding of the waves can cause the top of the arch to fall, leaving nothing but rock columns. These are called sea stacks. All of these features make rocky beaches beautiful, but also dangerous.

Rikoriko Cave

Rikoriko Cave

Matainaka Cave, New Zealand

Bundoran, Co. Donegal.

Sandstone sea Cave on Sand Island 07, Lake Superior, Apostle Islands National Lakeshore, Wisconsin

The battering of ocean waves also erodes seaside cliffs. It sometimes bores holes that form caves. When water breaks through the back of the cave, it creates an arch. The continual pounding of the waves can cause the top of the arch to fall, leaving nothing but rock columns. These are called sea stacks. All of these features make rocky beaches beautiful, but also dangerous.

Lunch Sea Arch at Cabo

Holei Sea Arch

The battering of ocean waves also erodes seaside cliffs. It sometimes bores holes that form caves. When water breaks through the back of the cave, it creates an arch. The continual pounding of the waves can cause the top of the arch to fall, leaving nothing but rock columns. These are called sea stacks. All of these features make rocky beaches beautiful, but also dangerous.

Old Harry Rocks

Lange Anna

Parus/Sail Rock

Kicker Rock

Bako Sea Stack

Haystack Rock

Ko Tapu

Risin og Kellingin

Old Man of Hoy

Twelve Apostles

Erosion by wind is known as Aeolian erosion and occurs almost always in deserts. Aeolian erosion of sand in the desert is partially responsible for the formation of sand dunes. The power of the wind erodes rock and sand.

Erosion by Wind

In dry areas, windblown sand blasts against rock with tremendous force, slowly wearing away the soft rock. It also polishes rocks and cliffs until they are smooth. Wind is responsible of the dramatic arches.

Erosion by Wind

Jebel Kharaz, Jordan

Grosvenor Arch, Utah, USA

Kolob Arch, Utah, USA

Shipton’s Arch, China

Sipapu Natural Bridge, Utah, USA

Steven’s Arch, Utah, USA

Double Arch, Utah, USA

Aloba Arch, Chad

Rainbow Bridge, Utah, USA

Delicate Arch, Utah, USA

Landscape Arch, Utah, USA

Árbol de Piedra, Altiplano, Bolivia

The erosive power of moving ice is actually a bit greater than the power of water but since water is much more common, it is responsible for a greater amount of erosion on the earth's surface.

Erosion by Ice

Glaciers erode predominantly by three different processes:

• Abrasion/Scouring• Plucking• Ice Thrusting

Erosion by Ice

The rocks carried by a glacier rub against the ground below, eroding both the ground and the rocks. Glaciers grind up rocks and scrape away the soil. Moving glaciers gouge out basins and form steep-sided mountain valleys. Eroded sediment is often visible on and around glaciers. This material is called moraine.

Erosion by Ice

Glacial moraines above Lake Louise, in Alberta, Canada

Mount Everest

Tustamena Glacier, Alaska

Alaska Glacier

Tustamena Glacier, Alaska

Tustamena Glacier, Alaska

Tustamena Glacier, Alaska

Alaska

Mass movement is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force of gravity. Mass movement is an important part of the erosional process, and is often the first stage in the breakdown and transport of weathered materials in mountainous areas.

Gravitational Erosion

Wadi in Makhtesh Ramon, Israel, showing gravity collapse erosion on its banks.

Exfoliation

• a type of erosion that occurs when a rock is rapidly heated up by the sun. This results in the expansion of the rock.

LightningWhen water in cracked rock is rapidly heated by a lightning strike, the resulting steam explosion can erode rock and shift boulders. It may be a significant factor in erosion of tropical and subtropical mountains that have never been glaciated. Evidence of lightning strikes include craters, partially melted rock and erratic magnetic fields.

Factors affecting erosion rates

• Precipitation and wind speed

• Soil structure and composition

• Vegetative cover• Topography

Human activities • Agricultural

practices• Deforestation• Roads and

urbanization• Climate change

Global Environmental Effects

Prevention and RemediationThe most effective known method for

erosion prevention is to increase vegetative cover on the land, which helps prevent both wind and water erosion.

Terracing is an extremely effective means of erosion control, which has been practiced for thousands of years by people all over the world.

Prevention and Remediation

Windbreaks (also called shelterbelts) are rows of trees and shrubs that are planted along the edges of agricultural fields, to shield the fields against winds.

Thank you for listening.

Prepared by:Ida Lyn A. AzueloBSED- Physics 2

Earth Science

EROSION