Physical (Mechanical) and Chemical WeatheringCreated By:Mr. Kreeger

Page References and Homework Page ReferencesPage 131-136HomeworkDo problems # 1a,b and c, 2a, 3a,b and c, 5aDo problems # 2b, 5b,c and d Do problem # 6

Table of ContentsWeathering DefinedTypes of Physical WeatheringFrost WedgingAbrasionWetting and dryingExfoliationPlant roots Lichen and mossTypes of Chemical WeatheringOxidationHydrolysis Carbonic AcidFactors affecting WeatheringHardnessSurface areaClimate

Introduction Video ClipWeathering

Weathering DefinedBreakdown of rocks into smaller particles by natural processesExposure to air, water and living things at or near the surface results in weatheringTwo Types Mechanical WeatheringChemical Weathering

Physical (Mechanical) Weathering Video Clip

1. Types of Physical (Mechanical) WeatheringPhysical (Mechanical) Weathering- The breakdown of rocks w/out changing chemical compositionsa. Frost Wedging- Water enters crack Freezes Expands Forces crack to open wider (Process repeats until rock splits)

Eventually, the rock splits from repeated frost action!

1. Types of (Physical) Mechanical Weathering contAbrasion- Process of rocks rubbing against each otherOccurs where fragments of rocks are carried along by streamsBreaks rocks into smaller pieces and makes them more rounded.Wind also weathers rock by abrasion. (Think about the beach)

1. Types of (Physical) Mechanical Weathering contc. Wetting and drying breaks up rocks that are made from clay When they are wet they expand, and they shrink as they dryAs this repeats over and over, the clay becomes weak and cracks (think of all the projects you have made out of claythey all crack and fall apart)!

1. Types of (Physical) Mechanical Weathering contd. Exfoliation soil and rock is removed (glaciers or uplifting), exposing rock found deep undergroundThis releases the pressure causing the surface of the rock to expand and eventually crack

1. Types of (Physical) Mechanical Weathering conte. Plant RootsThe deep roots of trees often break apart rocksf. Lichen & MossThese low to the ground plants can grow on rocks and eventually break them apart

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Which acitivity demonstrates chemical...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Landscapes will undergo the most chem...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Rock samples brough back from the mmo...

Introduction Clip to Chemical Weathering

2. Types of Chemical WeatheringChemical Weathering- The breakdown of rocks by changing their chemical compositions. (The presence of oxygen, water and Carbon Dioxide is most responsible)a. Oxidation- Oxygen reacts with many minerals especially those containing iron to form rust. (Occurs faster with water)

Chemical weathering of basalt

Iron Banding in Basalt

Oxidative weathering of mineral deposits (new deposits are white/yellow, weathered deposits are reddish-brown)

Video Clip about Oxidation

2. Types of Chemical Weathering cont b. Hydrolysis water (hydro) reacts with minerals such as feldspar and form clay

2. Types of Chemical Weathering contc. Carbonic acid carbon dioxide (CO) dissolves in water to form this acidcan cause minerals to dissolve, especially those containing calcite

Gnarled Rock a formation of limestone chemically weathered by acid rain

3. Factors affecting the rate of weathering

Rocks resistance to weathering (Hardness)

Amount of surface area

Climate

3. Factors affecting the rate of weathering cont..

Hardness and mineral composition- Limestone's most affected while granite is least affected.

The central area of rock was less resistant to weatheringthus the arch was formed!

3. Factors affecting the rate of weathering cont.. Surface AreaSurface area is the amount of rock surfaces exposed to the atmosphere

Greater surface area increases the rate of weathering

Weathering creates more surface area

3. Factors affecting the rate of weathering cont..ClimateThe temperature and moisture levels in an area over a long period of time.

Cold and Moist- Best for Physical Weathering

Warm and Moist- Best for Chemical Weathering

Dry Climate = Mechanical Weathering!Devils Marbles, Australia Mechanical weathering from wind and sand!

Warm Climate = Chemical WeatheringParthenon Athens, Greece

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Which geologic feature is caused prim...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Which change in climate would most li...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Water is a major agent of chemical we...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Which typ of climate has the greates ...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: In which climate would chemical weath...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Which process involves either a physi...

Dont forget: You can copy-paste this slide into other presentations, and move or resize the poll.Poll: Which property of water makes frost a...

Video Clip of Humans Impact of Weathering

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If you like, you can use this slide as a template for your own voting slides. You might use a slide like this if you feel your audience would benefit from the picture showing a text message on a phone.*Poll: Which property of water makes frost a...Press F5 or use the tool bar to enter presentation mode in order to see the poll.

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