WEATHERING AND EROSION

Rock Cycle

WEATHERING

I. Weathering - The breakdown of rock due to exposure to the atmosphere, weather, plants, and animals.

A. Mechanical Weathering (Physical Weathering) - Rock is split or broken into smaller material without changing its composition.

B. Chemical Weathering – Process by which rocks break down as a result of chemical reactions.

Mechanical (Physical)Weathering

1. Ice wedging (Porus, rocks with cracks (ice heaving/Frost Action)

2. Wetting and drying (for clay containing rocks)3. Plants (lichens, mosses, shrubs, trees)4. Exfoliation (the peeling away of surface layers)

due to the relief of pressure from rocks above it.5, Expansion / Contraction (Temperature)6. Abrasion- process of breaking down by means

of friction

ABRASION

ABRASION BY WATER

Abrasion – wears down or rounds

ABRASION BY WIND

MECHANICAL WEATHERING

Was once solid rock

MECHANICAL WEATHERING

ICE WEDGING

PLANTS

EXFOLIATION

Exfoliation – causes rock to sheet or flake off

Barrel cactus – breaking through rock to grow

EXFOLIATION

WEATHERING

B. Chemical Weathering - Break down of rocks when the rock minerals are changed to different substances.

Chemical Weathering1. Hydrolysis - chemical reaction with water and other

substances (feldspar, hornblende, augite) these combine to form clay.

2. Oxidation - chemical reaction with oxygen and other substances. (Iron bearing substances) , (red soil in Carolina & Virgina)

3. Carbonic acid/Carbonation - Carbon dioxide dissolves in H2O to form carbonic acid. (found in soda), P,Na,Mg and Ca (forms caves)

4. Acid Rain - sulfur from cars and coal/oil plants5. Plants/Animals (Lichens) - produce rock dissolving

acids

CHEMICAL WEATHERING

http://www.youtube.com/watch?v=Sw58a4yjFtc

Carbonation Clip

Details worn away by chemical weathering

Acid Rain

Oxidation

Hydrolysis -Reaction of any substance with water

Chemical Weathering-Water molecules "pull" apart a mineral (dissolve it)

Plants can grow on rocks and produce weak acids that can break down rock.

Organic WeatheringLichen breaking Lichen breaking

down rockdown rock

Bird dropping weathering

RATES OF WEATHERING

II. Rates of Weathering

1. The rocks themselves - Igneous and metamorphic most resistant, sedimentary least resistant because of pores.

2. Surface Area – More surface area = faster weathering

3. Climate - Warm and wet = chemical weathering

Cold and Dry = mechanical weathering

4. Topography

http://streaming.discoveryeducation.com/search/assetDetail.cfm?guidAssetID=6B1E329E-5A77-4B36-BFA9-1D307F75441C

Weathering

Get on the online book and go to chapter 14.

Select the visual concepts and watch the clips on physical and chemical weathering.

http://my.hrw.com/tabnav/controller.jsp?isbn=003036339x

EROSIONIV. EROSION- The breakup and removal of rock by moving natural agents (gravity, glaciers, wind, water)

A. Water Erosion

1. Rain

a. Sheet wash - thin sheets of soil removed prevent by - grass, continued plowing, crop rotation, strip crop, terraces

b.Gullying - valleys in sloped land - farms

2. Running water - most effective agent of erosion

a. stream, river, creek

b. Stream abrasion - grinding away of rock from bed or bank.

c. The faster the river moves = more “stuff” it can carry

EROSIONB. Wind Erosion - just as water; only less powerful

1. Abrasion - wearing down of particles

2.Deflation - removal of loose particles by wind - the most important effect by wind

3. Dunes - sand piled up, moved by wind

C. Glaciers – most powerful agent of erosion

Gullying

DEFLATION

DUNES

Arches National Park

Wind abrasion

EROSIONIV. EROSION- The breakup and removal of rock by moving natural agents (rivers, glaciers, wind, water)

A. Mass movements - Earth material down a slope caused by gravity.

1. Creep - Very, Very slow down slope movement of soil. (water in soil adds to it)

a. Talus - Loose rock fragments at base of cliffs

2. Landslides - sudden movement of bedrock or loose rocks down a cliff.

3. Slumps - small landslides on hills

4. Mudflow - fast movement of water saturated clay and silt.

5. Avalanche

TALUS

Landslide – mass movement

LANDSLIDE

LANDSLIDE

Landslide – mass movement

CREEP

Creep

SLUMPS

SLUMPS

SLUMP

MUDFLOW

The Colorado River weather and eroded way for 1,000s of years

Brought to us by the Colorado River