How does the Earth change over time?

GEOLOGICAL PROCESSES

Mantle

Core

Crust

Low-velocity zone

Solid

Outer core(liquid)

Innercore(solid)

35 km (21 mi.) avg., 1,200˚C

2,900km(1,800 mi.)3,700˚C

5,200 km (3,100 mi.), 4,300˚C

10 to 65km

100 km

200 km

100 km (60 mi.)200 km (120 mi.)

CrustLithosphere (crust and upper most

solid mantle)

Asthenosphere

Fig. 10.2, p. 212

STRUCTURE OF THE EARTH

ZONES OF EARTH’S STRUCTURE

• Core – solid• Mantle – thick solid zone

• Asthenosphere – under the rigid outermost part of the mantle – hot, partly melted rock that flows like plastic

• Crust – outermost and thinnest zone• Contains:

• CONTINENTAL CRUST - lies under continents and continental shelf

• OCEANIC CRUST – under ocean basins and covers 71% of earth’s surface

COMPOSITION OF EARTH’S CRUST

Earth’s Crust

Oxygen 46.6%

Silicon 27.7%

All others 1.5%

Magnesium 2.1%

Potassium 2.6%

Sodium 2.8%

Calcium 3.6%Iron 5.0%

Aluminum 8.1% Fig. 10.4, p. 213

FEATURES OF THE CRUST

Oceanic crust(lithosphere)

Abyssalhills Abyssal

floor

Oceanicridge

Trench

Volcanoes

Folded mountain belt

Craton (very stable)

Mantle (lithosphere)

Mantle (asthenosphere)

Abyss

al p

lain

Continental crust(lithosphere)

Mantle(lithosphere)

ContinentalriseContinental

slopeContinental

shelf Abyssal plain

Abyssalfloor

INTERNAL EARTHPROCESSES

Lithosphere

Asthenosphere

Oceanic ridge at a divergent plate boundary

Lithosphere

Trench Volcanic island arc

Asthenosphere

Risingmagma

Subductionzone

Trench and volcanic island arc at a convergent plate boundary

Fracture zone

Transformfault

Lithosphere

Asthenosphere

Transform fault connecting two divergent plate boundaries

• CONSTANT CHANGES

• INTERNAL PROCESSES – build up the planet’s surface

• Energy provided from heat in the interior

• Causes the mantle to deform and flow

• Two kinds of movements:

• CONVECTION CURRENTS

• MANTLE PLUMES – mantle flows upward in a column

PLATE TECTONICS• Movement of rigid plates called TECTONIC PLATES

caused by convection currents and mantle plumes

• Plates are 60 miles thick and are made up of continental and oceanic crust – called the LITHOSPHERE

• Plates are constantly moving on the asthenosphere at different speeds

• Concept accepted in early 1960’s was called continental drift theory

• Now called PLATE TECTONICS

• PRODUCES:

• VOLCANOES and EARTHQUAKES – found at plate boundaries

• OCEANIC RIDGE SYSTEM

• TRENCHES

Helps explain patterns of biological evolution!!!

Slide 6

Fig. 10.5b, p. 214

EURASIAN PLATE

CHINASUBPLATE PHILIPINE

PLATE

INDIAN-AUSTRLIAN PLATE

PACIFICPLATE

JUAN DEFUCA PLATE

COCOSPLATE

CARIBBEAN PLATE

NORTHAMERICAN

PLATE

SOUTHAMERICAN

PLATE

EURASIAN PLATE

ANATOLIAN PLATE

ARABIAN PLATE

AFRICAN PLATE

AFRICAN PLATE

CarlsbergRidge

Southwest IndianOcean Ridge

ANTARCTIC PLATE

Transformfault

East PacificRise

Transformfault

Mid-IndianOceanRidge

Southeast IndianOcean Ridge

Mid-AtlanticOceanRidge

ReykjanesRidge

Transformfault

Divergent ( ) andtransform fault ( )boundaries

Convergentplate boundaries

Plate motionat convergentplate boundaries

Plate motionat divergentplate boundaries

Slide 5

Fig. 10.5a, p. 214Volcanoes Earthquakes

TYPES OF BOUNDARIES

• DIVERGENT PLATE (Constructive Plate) BOUNDARIES - plates move in opposite directions

• Builds up the earth’s crust

Slide 7

Fig. 10.6a, p. 215

Lithosphere

Asthenosphere

Oceanic ridge at a divergent plate boundary

MID-ATLANTIC RIDGE SYSTEM

• CONVERGENT PLATE– plates are pushed together by internal forces

• Oceanic lithosphere is sub-ducted under the continental at subduction zones

• Trenches normally form at the boundary

Slide 8

Fig. 10.6b, p. 215

Lithosphere

Trench Volcanic island arc

Asthenosphere

Risingmagma

Subductionzone

Trench and volcanic island arc at a convergentplate boundary

TYPES OF BOUNDARIES

TYPES OF BOUNDARIES

• Transform faults – occur when plates slide past one another along a fracture (fault) in the lithosphere• Most are on the ocean

floor

Slide 9

Fig. 10.6c, p. 215

Fracture zone

Transformfault

Lithosphere

Asthenosphere

Transform fault connecting two divergent plate boundaries

EXTERNAL GEOLOGIC PROCESSES• Based directly or indirectly on energy from the sun and gravity (tend to

wear down the earth’s surface)

• Two types:

• EROSION - material is dissolved, loosened, or worn away at one part of the earth’s surface and deposited somewhere else (Caused by wind, water, and human activities).

• WEATHERING – produces loosened material that can be eroded

• MECHANICAL – large rock fragments broken into smaller pieces (One type called FROST WEDGING- caused by freezing, expansion, and splitting of rock)

• CHEMICAL – chemical reactions decompose a mass of rock mainly reacts with oxygen, carbon dioxide, and water in the atmosphere and ground

MINERALS AND ROCKS• Mineral

• Either an ELEMENT or INORGANIC COMPOUND – naturally occurring and a solid

• Some are single elements – Au, Ag, most are compounds – mica, salt, quartz

• Rock

• Any material that makes up a large natural continuous part of the earth’s crust

• Can contain only one mineral but most consist of two or more minerals

• Example: GRANITE – quartz, mica, and feldspar

• FORMS FROM MOLTEN ROCK MATERIAL (MAGMA)

• Wells up from upper mantle or deep crust, cools, hardens into rock – EXAMPLE: GRANITE

• Igneous Rock FORMS FROM LAVA

• Forms above ground when magma cools

• Main part of earth’s crust

• Source of many nonfuel mineral resources

Igneous RockGranite, Pumice,

Basalt

Sedimentary RockShale, Sandstone,

Limestone

Metamorphic RockSlate, Quartzite,

Marble

Magma(Molten Rock)

WeatheringWeathering

ErosionErosion

TransportTransport DepositionDeposition

External ProcessesInternal ProcessesExternal ProcessesInternal Processes

Heat,Pressure

Heat,Pressure

Heat,

Pressure

Heat,

Pressure

Fig. 10.8, p. 217

THE ROCK CYCLE

NATURAL HAZARDS: EARTHQUAKES

• Caused by stress in crust which deforms rock until it fractures producing faults. This faulting or abrupt movement causes EARTHQUAKES

• Energy is released as shock waves which move outward• Focus - point of initial movement• Epicenter – point on earth’s surface above the focus• Magnitude – measures severity of earthquake

• Richter scale-measured on a seismograph• Ranked as:

Insignificant – less than 4 Minor (4.0 – 4.9)

Damaging (5.0 – 5.9) Destructive (6.0 – 6.9) Major (7.0 – 7.9) Great (over 8.0)

*Amplitude for each is 10 x greater than the next smaller unit

MORE …

AFTERSHOCKS– smaller earthquakes that follow – often over a period of months

FORESHOCKS – seconds to weeks before the main shock

PRIMARY EFFECTS - shaking, sometimes permanent vertical or horizontal displacement of earth

SECONDARY EFFECTS - rock slides, fires, flooding, tsumanis

EARTHQUAKESLiquefaction ofrecent sedimentscauses buildingsof sink

Landslides mayoccur onhilly ground

Shockwaves

Epicenter

Focus

Two adjoining platesmove laterally alongthe fault line

Earth movementsCause flooding inLow-lying areas

EXPECTED EARTHQUAKE DAMAGE

Canada

United States

No damage expected

Minimal damage

Moderate damage

Severe damage

REDUCING EARTHQUAKE DAMAGE• EXAMINE HISTORICAL RECORDS AND

MAKE GEOLOGICAL MEASUREMENT

• MAP HIGH RISK AREAS

• ESTABLISH BUILDING CODES

• TRY TO PREDICT WHERE AND WHEN EARTHQUAKES WILL OCCUR

NATURAL HAZARDS: VOLCANOES

• MAGMA REACHES THE EARTH’S SURFACE THROUGH A VENT OR CRACK• RELEASES:

• EJECTA – CHUNKS THROUGH ASH

• LIQUID LAVA

• GASES – water vapor, carbon dioxide, sulfur dioxide

• USUALLY FOUND IN SAME AREAS AS EARTHQUAKE ACTIVITY

• BENEFITS:• FORM MOUNTAINS, LAKES, ISLANDS,

AND PRODUCE FERTILE SOILS AS LAVA WEATHERS

VOLCANIC ERUPTIONSextinct

volcanoes

magmareservoir

centralvent

magmaconduit

Solidlithosphere

Upwellingmagma Partially molten

asthenosphere

TYPES OF VOLCANOES

REDUCE VOLCANIC HAZARDS

• LAND – USE PLANNING

• BETTER PREDICTION

• EFFECTIVE EVACUATION PLANS