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Environmental ScienceEnvironmental ScienceUnit 1: Geology BasicsUnit 1: Geology Basics

Earth’s Layers & Plate Earth’s Layers & Plate TectonicsTectonics

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Lithosphere vs Lithosphere vs AsthenosphereAsthenosphere• Lithosphere: Crust + upper MantelLithosphere: Crust + upper Mantel

– 80 km deep (50 miles)80 km deep (50 miles)– Less dense than AsthenosphereLess dense than Asthenosphere– Floats on the AsthenosphereFloats on the Asthenosphere– Plates move slowly! 2”/yrPlates move slowly! 2”/yr

• Asthenosphere:Asthenosphere:– Fluid part of Mantel—ductile, like puttyFluid part of Mantel—ductile, like putty– Underneath the LithosphereUnderneath the Lithosphere

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Shape of Earth’s SurfaceShape of Earth’s Surface• Main force: Movement of Earth’s Main force: Movement of Earth’s

outer layer by the process of: outer layer by the process of: – PLATE TECTONICSPLATE TECTONICS

• What is a “tectonic plate”?What is a “tectonic plate”?– Earth’s crust is made up of ~12 “plates” Earth’s crust is made up of ~12 “plates”

that fit together like a jigsaw puzzle.that fit together like a jigsaw puzzle.•Plates have continental and ocean crust.Plates have continental and ocean crust.•Plates move around, causing: Earthquakes, Plates move around, causing: Earthquakes,

Volcanoes, Mountain Building, and much of Volcanoes, Mountain Building, and much of the Rock Cycle.the Rock Cycle.

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Processes that change Earth’s Processes that change Earth’s surface:surface:

• Weathering & ErosionWeathering & Erosion– WeatheringWeathering

•ChemicalChemical

•PhysicalPhysical

– WindWind– WaterWater

• VolcanismVolcanism

• DeformationDeformation

Plate MovementsPlate Movements

• Converging Plates – plates moving Converging Plates – plates moving together, form trenchestogether, form trenches

• Diverging Plates – Plates moving Diverging Plates – Plates moving apart, form mid-oceanic ridgesapart, form mid-oceanic ridges

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What is “Subduction” ?What is “Subduction” ?

• Two sections of crust collideTwo sections of crust collide– One slab is forced down deep into EarthOne slab is forced down deep into Earth

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VolcanismVolcanism

• Bring Magma to the surfaceBring Magma to the surface

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VolcanismVolcanism

• The most general cause of volcanism The most general cause of volcanism on earth is Subduction of earth’s on earth is Subduction of earth’s crust.crust.– One tectonic plate is forced under One tectonic plate is forced under

another plate as the plates push another plate as the plates push together.together.

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Mid-Ocean RidgesMid-Ocean Ridges• Bottom of sea splits apart:Bottom of sea splits apart:

– Magma risesMagma rises– New Crust formedNew Crust formed

• ““Spreading Ridges”Spreading Ridges”– Lithosphere slides away from elevated Lithosphere slides away from elevated

regionregion•4 cm/yr4 cm/yr

– Central portions of oceansCentral portions of oceans

RiftingRifting• Continents can also Continents can also

split apart at “rifts”.split apart at “rifts”.– Continued rifting can Continued rifting can

form a new ocean.form a new ocean.

Chemical WeatheringChemical Weathering• Minerals in rocks are dissolved into Minerals in rocks are dissolved into

rainwater or changed from one type of rainwater or changed from one type of mineral into another.mineral into another.

• Occurs most readily in warm, moist areas.Occurs most readily in warm, moist areas.– Warm speeds up chemical reactions.Warm speeds up chemical reactions.– Water is required for chemical weathering.Water is required for chemical weathering.

• Minerals differ in their resistance to Minerals differ in their resistance to chemical weathering.chemical weathering.– Quartz resists chemical weathering.Quartz resists chemical weathering.– Feldspar does not resist well.Feldspar does not resist well.

• Breaks down into clay minerals.Breaks down into clay minerals.

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Chemical WeatheringChemical Weathering

• Ever been to a cave?Ever been to a cave?– Caverns develop as water flows Caverns develop as water flows

underground, dissolving minerals in rock underground, dissolving minerals in rock and transporting them away.and transporting them away.•Cave features, such as stalactites and Cave features, such as stalactites and

stalagmites form when mineral-carrying stalagmites form when mineral-carrying water drips and leaves behind some of its water drips and leaves behind some of its mineral load.mineral load.

CaveCave

• Stalactites “Hang Stalactites “Hang on tight” to the on tight” to the ceiling.ceiling.– Form as minerals Form as minerals

come out of water come out of water as a drip forms.as a drip forms.

• ““Mighty” Mighty” StalagmitesStalagmites– Form as minerals Form as minerals

come out of water come out of water after it drips to the after it drips to the floor.floor.

Physical WeatheringPhysical Weathering• Rocks are broken apart into smaller Rocks are broken apart into smaller

pieces by water and other forces.pieces by water and other forces.– Moving liquid water can break rock Moving liquid water can break rock

apart by knocking rocks together.apart by knocking rocks together.•Rivers, Ocean surf, etc.Rivers, Ocean surf, etc.

– Glaciers break, grind, and move rock.Glaciers break, grind, and move rock.– Water can break rock as it freezes in Water can break rock as it freezes in

cracks.cracks.•Water expands as it freezes, and can exert Water expands as it freezes, and can exert

tremendous forces. Potholes in roads and tremendous forces. Potholes in roads and exploding soda cans show the power of exploding soda cans show the power of freezing water.freezing water.

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SoilSoil

• Bits of broken rocks + remains of Bits of broken rocks + remains of plants & animalsplants & animals

SoilSoil

• Soil Horizon – Each Soil Horizon – Each

layer of soil in a soillayer of soil in a soil

profileprofile

• Soil Profile – The Soil Profile – The

arrangement of the arrangement of the

layers of soil in an arealayers of soil in an area

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What is a “Fault” ?What is a “Fault” ?

• Fracture due to stress on rockFracture due to stress on rock• Cause: pushing & shoving of crust:Cause: pushing & shoving of crust:

– Seafloor spreadingSeafloor spreading

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Making MountainsMaking Mountains

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Making MountainsMaking Mountains

• FoldingFolding– Colliding plates—neither is subductedColliding plates—neither is subducted– Plates crash and rise verticallyPlates crash and rise vertically