Forces of Change Formula:

+ =

The Earth’s

Builders and Landscapers!!!!!!

Main IdeaMain Idea: Together with the : Together with the internal forces internal forces of of plate tectonicsplate tectonics, , the the externalexternal forces forces of of weathering weathering

and erosionand erosion are constantly are constantly changing the appearance of the changing the appearance of the

earth’s surface.earth’s surface.

Landscaping the Earth: Landscaping the Earth: Weathering and ErosionWeathering and Erosion

WeatheringWeathering –process that breaks –process that breaks down rock into smaller piecesdown rock into smaller pieces

Two waysTwo ways:: physical (or mechanical) physical (or mechanical)

weatheringweathering – when physical – when physical processes break apart rocksprocesses break apart rocks

chemical weatheringchemical weathering – occurs – occurs when changes are made to the when changes are made to the chemical make-up of rocks that chemical make-up of rocks that cause them to break apartcause them to break apart

Physical Weathering Examples:Physical Weathering Examples:

frost wedgingfrost wedging – where water – where water seeps into cracks of rocks and seeps into cracks of rocks and freezes; freezes; iceice expands causing expands causing the rock to split the rock to split

tree rootstree roots grow through cracks grow through cracks of rocks eventually forcing of rocks eventually forcing rocks apartrocks apart

Chemical Weathering ExamplesChemical Weathering Examples::

underground cavesunderground caves form when form when carbon dioxide combines with carbon dioxide combines with water and dissolves limestonewater and dissolves limestone

oxidationoxidation - rocks that contain - rocks that contain iron can rust just like iron does; iron can rust just like iron does; as the rust expands, it helps to as the rust expands, it helps to break up rockbreak up rock

ErosionErosion – the transporting of weathered – the transporting of weathered material from one place to another material from one place to another

Three Agents of Erosion:Three Agents of Erosion: WaterWater WindWind IceIce

WATER: WATER: Nature’s Scouring PadNature’s Scouring Pad

RIVERSRIVERS:: most important agent of erosionmost important agent of erosion rainfall/snowmelt forms into creeks, streams, and/or rainfall/snowmelt forms into creeks, streams, and/or

rivers carrying rocks, pebbles, and sedimentrivers carrying rocks, pebbles, and sediment sourcesource: beginning of river: beginning of river mouthmouth: where it empties: where it empties tributarytributary: river that feeds into another river: river that feeds into another river abrasionabrasion – when rivers cut and scour the landscape – when rivers cut and scour the landscape

into channels and into channels and V-shaped valleysV-shaped valleys as they carry as they carry weathered materialweathered material

sometimes valleys are carved even further to form sometimes valleys are carved even further to form high, steep walls called high, steep walls called canyonscanyons

muddy watermuddy water is a sign that erosion is taking place b/c is a sign that erosion is taking place b/c that means that bits of rock and soil are in the waterthat means that bits of rock and soil are in the water

depositiondeposition of sediment from moving water can result of sediment from moving water can result in:in:

- - alluvial fansalluvial fans at mountain bases at mountain bases - - deltasdeltas at mouths of rivers at mouths of rivers

Water Continued….Water Continued….

WAVES:WAVES:

Waves crashing against shores can:Waves crashing against shores can: change shape of coastlineschange shape of coastlines build up and tear down beachesbuild up and tear down beaches reduce the coastline (coastal reduce the coastline (coastal

erosion)erosion) form caves and archesform caves and arches pound rocks into sand pound rocks into sand

WINDWINDNature’s SandblasterNature’s Sandblaster

Wind is capable of carrying dust, sand, soil, and Wind is capable of carrying dust, sand, soil, and volcanic ashvolcanic ash

Wind sculpts or Wind sculpts or ““sand-blastssand-blasts”” land surfaces into land surfaces into very unusual formations very unusual formations

Wind forms Wind forms sand dunessand dunes because unlike water and because unlike water and ice, sediment can be moved ice, sediment can be moved uphill or downhilluphill or downhill ….constantly moving and changing shape….constantly moving and changing shape

Dunes are found along coastlines, deserts, lakes, Dunes are found along coastlines, deserts, lakes, and riversand rivers

Beach dunes attract Beach dunes attract vegetationvegetation. This helps to . This helps to reduce reduce coastal erosioncoastal erosion, but protective dunes are , but protective dunes are often damaged or destroyed due to human often damaged or destroyed due to human development and weather-related occurrences.development and weather-related occurrences.

Barrier islandsBarrier islands are islands that have dunes that are islands that have dunes that help to protect inland areas from help to protect inland areas from coastal erosioncoastal erosion

GLACIERS:GLACIERS:Nature’s BulldozersNature’s Bulldozers

ice sheets or capsice sheets or caps - vast glaciers that covered large - vast glaciers that covered large portions of the earth’s surface during the last ice age. portions of the earth’s surface during the last ice age.

What’s left of these ice caps still exist and cover much of What’s left of these ice caps still exist and cover much of Antarctica,Antarctica, GreenlandGreenland, and the , and the Arctic OceanArctic Ocean

mountain glaciersmountain glaciers – form when fallen snow accumulates – form when fallen snow accumulates in mountain tops year after year eventually turning into in mountain tops year after year eventually turning into ice; once heavy enough, gravity pulls these glaciers ice; once heavy enough, gravity pulls these glaciers downhilldownhill

all all glaciers move slowlyglaciers move slowly picking up soil, rocks, boulders, picking up soil, rocks, boulders, trees, etc.trees, etc.

Glaciers carve out Glaciers carve out U-shaped valleysU-shaped valleys (Yosemite) (Yosemite) Glaciers gouge out basins that eventually become lakes Glaciers gouge out basins that eventually become lakes

(Great Lakes and Lakes of Canada)(Great Lakes and Lakes of Canada) As glaciers begin to As glaciers begin to retreatretreat (melt), they deposit (melt), they deposit

boulders, rocks, soil, and sediment called boulders, rocks, soil, and sediment called morainemoraine..

Weathering and Erosion Weathering and Erosion Miscellaneous Miscellaneous

Effects of weathering and erosion can create Effects of weathering and erosion can create spectacular sceneryspectacular scenery which many governments protect which many governments protect as national parks and other federally protected landsas national parks and other federally protected lands

Every physical land feature on earth was formed by the Every physical land feature on earth was formed by the combinationcombination of plate tectonics and weathering and of plate tectonics and weathering and erosion…..so, don’t forget the formula!!!erosion…..so, don’t forget the formula!!!

Unfortunately, Unfortunately, humans speedhumans speed up these naturally up these naturally occurring effects at alarming rates with dire occurring effects at alarming rates with dire consequences. Examples include:consequences. Examples include:

- acid rain- acid rain- poor farming practices- poor farming practices- deforestation- deforestation- urbanization- urbanization- strip mining- strip mining- - building levees!!!!building levees!!!!