Earth Earth

NotesNotes

Chapter 2 ~ Chapter 2 ~ Section 2Section 2Forces of Forces of ChangeChange

The Earth’s The Earth’s InteriorInterior

Inner CoreInner Core – – about 4,000 about 4,000 miles below the miles below the surface of the surface of the EarthEarth

Outer CoreOuter Core – – 1,400 miles 1,400 miles thick, thick, temperature temperature reaches 8500reaches 8500°F°F

Earth’s Interior Earth’s Interior (con’t)(con’t)

MantleMantle: layer of hot, dense rock – MAGMA: layer of hot, dense rock – MAGMA

Earth’s Interior Earth’s Interior (con’t)(con’t) CrustCrust: rocky shell forming Earth’s : rocky shell forming Earth’s

surface.surface.

The crust is broken into slabs of rock The crust is broken into slabs of rock called plates.called plates.

NNatural forces interact with the crust, atural forces interact with the crust, creating landforms on the surface of creating landforms on the surface of the earth.the earth.

Below the oceans, the crust is about 5 Below the oceans, the crust is about 5 miles thick. Below the continents it miles thick. Below the continents it averages 22 miles in thickness.averages 22 miles in thickness.

Earth’s Interior Earth’s Interior (con’t)(con’t) Plates - Plates - float on a melted layer in the upper mantlefloat on a melted layer in the upper mantle

- carry the earth’s oceans and continents- carry the earth’s oceans and continents

InternaInternal l

Forces Forces of of

ChangeChange

The The lithosphere lithosphere — the earth’s — the earth’s crust and upper layer of the crust and upper layer of the mantle — is broken into a mantle — is broken into a number of large, moving plates.number of large, moving plates.

The Plate Tectonic Theory

The plates slide very slowly over a The plates slide very slowly over a hot, pliable layer of mantle.hot, pliable layer of mantle.

The earth’s oceans and continents ride atop of the plates.

It’s along the plate boundaries that most earthquakes and volcanoes occur due to friction and pressure that produces heat.

The Plate Tectonic Theory

Plate MovementPlate Movement

Plate movementPlate movement:: creates oceans and creates oceans and mountain rangesmountain ranges

Plate Plate MovemMovem

entent Continental Continental DriftDrift: the : the theory that theory that the the continents continents were once were once joined and joined and then slowly then slowly drifted apartdrifted apart

Plate MovementPlate Movement

PangaeaPangaea: gigantic super : gigantic super continent which continent which eventually broke aparteventually broke apart

Observe an Observe an animation of the animation of the

breakup of breakup of PangaeaPangaea

http://www.classzone.com/books/http://www.classzone.com/books/earth_science/terc/content/visualizations/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?es0806/es0806page01.cfm?chapter_no=visualization chapter_no=visualization

Examine an Examine an animation of animation of

plate movement plate movement predicted for the predicted for the

futurefuture http://www.classzone.com/books/earth_science/http://www.classzone.com/books/earth_science/

terc/content/visualizations/es0807/terc/content/visualizations/es0807/es0807page01.cfm?chapter_no=visualization es0807page01.cfm?chapter_no=visualization

Ring of FireRing of Fire A A circle of volcanic mountains

surrounding the Pacific Ocean It is one of the most earthquake-prone It is one of the most earthquake-prone

& volcano-prone areas on the planet.& volcano-prone areas on the planet. Hot SpotsHot Spots are hot regions deep

within the mantle that produce magma, which rises to the surface. Volcanic island chains form as oceanic plates drift over the hot spot.

Example: Hawaiian Islands http://www.classzone.com/books/earth_science/terc/content/http://www.classzone.com/books/earth_science/terc/content/

visualizations/es0904/es0904page01.cfm?chapter_no=visualization visualizations/es0904/es0904page01.cfm?chapter_no=visualization

VolcanoesVolcanoes Form when magma inside the earth Form when magma inside the earth

breaks through the crust. Lava flows breaks through the crust. Lava flows and may produce a large, cone-shaped and may produce a large, cone-shaped mountainmountain

They often form along plate boundariesThey often form along plate boundaries

Magma splits the earth’s surface when Magma splits the earth’s surface when plates collideplates collide

FaultFault—a break in the earth’s —a break in the earth’s crust. Movement along a fault crust. Movement along a fault can send out shock waves, can send out shock waves, causing an causing an earthquakeearthquake..

San Andreas FaultSan Andreas Fault

San Andreas San Andreas FaultFault

A devastating fire followed the 1906 earthquake in San Francisco

The San Fernando earthquake of 1971 collapsed freeway overpasses in southern California

Converging/Converging/Collision ZoneCollision Zone

Plates collide and push slowly Plates collide and push slowly against each other and form a against each other and form a collisioncollision or or converging zoneconverging zone..

If 2 oceanic plates collide, 1 slides If 2 oceanic plates collide, 1 slides under the other. Islands often under the other. Islands often form this way.form this way.

If 2 continental plates collide, If 2 continental plates collide, mountains are formed. Example: mountains are formed. Example: HimalayasHimalayas

Continental Crush / Continental Crush / CollideCollide

Spreading ZoneSpreading ZonePlates pull away from each Plates pull away from each

other and form a other and form a spreading spreading zonezone. . These areas are likely to have These areas are likely to have earthquakes, volcanoes, and earthquakes, volcanoes, and rift valleysrift valleys (a large split (a large split along the crest of a mountain).along the crest of a mountain).

http://www.classzone.com/books/http://www.classzone.com/books/earth_science/terc/content/visualizations/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?es0804/es0804page01.cfm?chapter_no=visualization chapter_no=visualization

Spreading ZoneSpreading Zone

SubductionSubductionThey meet, or They meet, or CONVERGE CONVERGE and and

form a form a subduction zonesubduction zone. . *If an oceanic plate collides with *If an oceanic plate collides with a continental plate, the heavier a continental plate, the heavier oceanic plate will slide under the oceanic plate will slide under the lighter, continental plate. lighter, continental plate. This results in volcanic mountain This results in volcanic mountain building and earthquakes.building and earthquakes.

SubductionSubduction

ExternExternal al

Forces Forces of of

ChangeChange

External ForcesExternal Forces What other forces can create landforms?What other forces can create landforms?

WeatheringWeathering – a process that breaks down – a process that breaks down rock at or near the surface into smaller rock at or near the surface into smaller pieces. pieces.

- This is a VERY slow process – thousands - This is a VERY slow process – thousands to millions of years.to millions of years.

Mechanical Mechanical (or Physical) WeatheringWeathering occurs when rock occurs when rock freezes – it can cause freezes – it can cause Frost Frost WedgingWedging, a crack in the rock , a crack in the rock caused by freezing.caused by freezing.

Chemical WeatheringChemical Weathering – –

alters the rock’s chemical alters the rock’s chemical

makeup by changing the makeup by changing the

minerals. This can actually minerals. This can actually

change one kind of rock into change one kind of rock into another.another. Important forces in Important forces in Chemical Chemical

WeatheringWeathering are moisture and carbon are moisture and carbon dioxide. dioxide. Through this process caves are created.Through this process caves are created.

Acid RainAcid Rain causes another type of causes another type of chemical weathering that destroys chemical weathering that destroys forests, pollutes water and kills wildlife.forests, pollutes water and kills wildlife.

Over thousands of years, areas with Over thousands of years, areas with limestone rocks can develop caves. limestone rocks can develop caves.

Groundwater dissolves a network of Groundwater dissolves a network of tunnels in the rock. If the water table tunnels in the rock. If the water table is lowered by a change in climate or is lowered by a change in climate or tectonic uplift of the area, tectonic uplift of the area, groundwater drains out of the tunnels, groundwater drains out of the tunnels, leaving the caverns exposed to air.leaving the caverns exposed to air.

http://www.classzone.com/books/earth_science/terc/content/http://www.classzone.com/books/earth_science/terc/content/visualizations/es1405/es1405page01.cfm?visualizations/es1405/es1405page01.cfm?chapter_no=visualization chapter_no=visualization

EROSIONEROSION ErosionErosion is the is the

movement of movement of weathered weathered materials materials including gravel, including gravel, soil and sand. soil and sand.

The most common The most common agents of erosion agents of erosion are are water, wind water, wind and glaciers.and glaciers.

WATER AND EROSIONWATER AND EROSION

Moving WaterMoving Water (rain, rivers, (rain, rivers, streams and oceans) is the streams and oceans) is the greatest agent of erosion.greatest agent of erosion.

SedimentSediment – small particles of soil, – small particles of soil, sand, and gravel - is carried by sand, and gravel - is carried by the moving water and works like the moving water and works like sandpaper to grind away rocks.sandpaper to grind away rocks.

ErosioErosionnSullivan Sullivan Falls Falls Rickett’s Rickett’s Glen State Glen State Park Park PennsylvaPennsylva

nia nia

SedimentSediment Sediment from Sediment from

the River Rhône the River Rhône flowing into flowing into Lake Geneva.Lake Geneva.

http://www.classzone.com/books/http://www.classzone.com/books/earth_science/terc/content/earth_science/terc/content/visualizations/es0604/visualizations/es0604/es0604page01.cfm?es0604page01.cfm?chapter_no=visualization chapter_no=visualization

SedimentSediment

Sediment creates new Sediment creates new landforms such as landforms such as

floodplains & deltas.floodplains & deltas.FloodplainsFloodplains DeltasDeltas form at the mouth of form at the mouth of

a rivera river

Wind ErosionWind Erosion The second major cause The second major cause

of erosion is of erosion is windwind, , especially where there is especially where there is little water and few little water and few plants.plants. Wind ErosionWind Erosion can can

devastate one area devastate one area while benefiting while benefiting another – HOW?another – HOW?LoessLoess – windblown – windblown deposits of mineral-deposits of mineral-rich dust rich dust

GLACIERS CAUSE GLACIERS CAUSE EROSION?EROSION?

GlaciersGlaciers are slow are slow moving moving sheets of sheets of ice that ice that are are formed formed over over many many years.years.

GLACIERSGLACIERS

How do they cause erosion?How do they cause erosion?

The movement cuts through land The movement cuts through land creating lakes.creating lakes.

They melt away and then rebuild They melt away and then rebuild again over thousands of years.again over thousands of years.