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The Dynamic Earth

Chapter 3

The Earth as a System

• The Earth is an integrated system– Geosphere - rock, soil and sediments– Atmosphere - the air we breathe– Hydrosphere - All of the water on or near

the earth’s surface– Biosphere - part of the earth where life

exists• 9km above the earth’s surface to the bottom of

the ocean

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The Geosphere

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The Earth’s Interior

• Seismic waves - the waves that travelthrough the interior of the earth duringan earthquake.

• Seismic waves are used in order todetermine the make up of the Earth’interior– Measure the speed and direction of the

waves.– The waves change depending on the type

of material it passes through

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The Composition of the Earth

• Three layers based on the composition ofeach layer

• Made up of three layers that get progressivelydenser

• Crust– Thin outer layer– Light elements– Less than 1% of the planet’s mass– 5-8km thick beneath the oceans– 20-70km thick beneath the continents

The Composition of the Earth

• Mantle– Layer beneath the crust– 64% the mass of the earth– 2,900km thick– Rocks of medium density

• Core– Densest elements– 3,400km thick

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The Structure of the Earth

• The Earth can be divided into five layersbased on the physical properties of eachlayer.

• Lithosphere– Outer layer– Cool, rigid layer– 15-300km thick and includes the crust and upper

mantle– Divided into tectonic plates

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The Structure of the Earth• Asthenosphere

– Beneath the lithosphere– 250km thick– Solid layer of the mantle that flows very slowly.– Tectonic plates move on top of it.

• Mesophere– The lower part of the mantle– 2,550km thick

• Outer core– Dense liquid layer made up of iron and nickel– 2,200km thick

• Inner core– Dense and solid iron and nickel– 1,228km thick

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Plate Tectonics• Tectonic plates

– Part of the lithosphere– Glide across the asthenosphere– Continents move with them

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Plate Boundaries

• Plate boundaries are regions ofgeologic activity– Mountains form– Earthquakes occur– Volcanoes erupt

Plate Tectonics and MountainBuilding

• Plates collidingcauses the formationof mountains

• Example-Himalayasformed from thecollision of the Asianand Indian Plates

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Earthquakes• Fault - break in the Earth’s crust along

plate boundaries.• Plate boundaries slip past each other• When rocks break as the plates slip

earthquakes occur.• Most active earthquake zones occur

along plate boundaries• Richter scale - Quantifies the amount of

energy released by an earthquake

Earthquakes• Magnitude - the measure of

energy released by anearthquake.

• Smallest magnitude - 2.0• Largest magnitude - 9.5• Each magnitude is 31.7 times

more energy than the numberbelow it.

• Example - a magnitude of 6releases 31.7 times more energythan a magnitude of 5

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Volcanoes• Volcano - mountain built from magma

that rises form the Earth’s interior to thesurface

• Can occur in land or under the sea.• Most occur along tectonic plate

boundaries.

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Volcanoes• Local effects

– Human loss– Buildings collapse– Bury crops– Health problems - difficulty breathing

• Global effects– Ash and gas reduces the amount of sunlight that

reaches the earth.– Change the Earth’s climate for years by causing a

drop in the global temperature

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Erosion• Erosion - The removal and

transport of surface material• Erosion is caused by wind

and water• Erosion wears down rocks

and makes them smoother.• Erosion moves soil

The Atmosphere

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Composition of the Atmosphere• Atmosphere - the mixture of gases

which surrounds the Earth• Nitrogen makes up 78% of the gases.

– Enters the atmosphere when volcanoeserupt and dead animals and plants decay.

• Oxygen makes up 21% of the gases– Primarily produced by plants

Air Pressure

• Gravity pulls the atmosphere towardsthe Earth’s surface

• The atmosphere is 30km from theground

• The atmosphere is denser near theEarth’s surface

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Layers of the Atmosphere

• Layers of the atmosphere based ontemperature changes.

• Troposphere– Nearest the Earth’s surface– Extends 18km– Almost all weather occurs in this layer.– Densest layer– Temperature decreases as altitude increases

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Layers of the Atmosphere

• Stratosphere– Above the troposphere– Between 18-50km– Temperature rises as altitude increases

due to the absorption of UV rays by theozone.

– Ozone - Absorbs ultraviolet readiationwhich can damage living cells

Layers of the Atmosphere• Mesophere

– Between 50-80km.– Coldest layer - as low as -93°C

• Thermosphere– Nitrogen and Oxygen absorb solar radiation.– Temperatures as high as 2,000°C– Air is very thin– Lower thermosphere absorbs x-rays and gamma

rays resulting in the formation of ions– Ionosphere - the lower thermosphere– Sometimes these ions radiate the energy as light.

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Energy in the Atmosphere• Energy from the sun is transferred in

Earth’s atmosphere– Radiation - transfer of energy across space

and in the atmosphere– Conduction - flow if heat from a warmer

object to a colder object when they are incontact with each other.

– Convection - transfer of heat by air currents.• Hot air rises and cold air sinks

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Heating of the Atmosphere

• The Earth only receives about two billionthsof the energy from the sun

• The energy which does reach the earth istremendous

• About half of the solar energy reaches thesurface of the Earth

• The rest of the energy is absorbed orreflected by clouds, gases, dust or the earth’ssurface.

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Movement of Energy in the Atmosphere• Warm air rises in the troposphere and cold

air sinks.• Convection currents - The process of

warming and cooling.• Creates winds• Distributes heat around the Earth.

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Greenhouse Effect• Sunlight heats the surface of the earth.• Some of the heat is reflected back into the

atmosphere and escapes into space• Some of the heat is reflected back into the

atmosphere and is trapped by greenhousegases.

• Greenhouse Effect - Gases trap heat near thesurface of the Earth

• Greenhouse gasses - carbon dioxide,methane, and nitrous oxide, water vapor

Greenhouse Effect• Without the greenhouse effect the Earth

would be too cold for life

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Hydrosphere and Biosphere

Hydropshere and the Water Cycle

• Hydrosphere - all ofthe water on or nearthe Earth’s surface

• Water cycle - themovement of waterinto the air, ontoland and then backto the water.

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Hydropshere and the Water Cycle

• Evaporation - liquid water is heated bythe sun and then rises into theatmosphere as water vapor

• Condensation - water vapor forms waterdroplets

• Precipitation - large water dropletswhich fall from the clouds.

Earth’s Oceans

• World ocean - single, large interconnectedbody of water.

• Covers 70% of the Earth’s surface• Regulates the Earth’s climate• Largest - Pacific• Atlantic• Indian• Arctic - Smallest

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Earth’s Oceans

Ocean Water

• Ocean water contains salt• NaCl makes up more than 85% of the

salt• Salinity - total quantity of dissolved salts• Average salinity is 3.5% by weight• Salinity can vary by location.

– Rain, evaporation, fresh water

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Temperature Zones

• Surface zone– warmed by the sun

• Thermocline– Boundary between the warm and cold water– Temperature falls rapidly with depth

• Deep zone– Below the thermocline– Very cold

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Global Temperature Regulator

• The ocean absorbs and stores over50% of heat from the sun

• Absorbs and releases heat more slowlythan the land

• Regulates the temperature of theatmosphere

• Ocean currents transports heat aroundthe globe

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Ocean Currents

• Currents - movement of water thatoccur at or near the ocean surface.

• Currents are driven by global windpatterns

• Currents influence the climate of theland areas they flow past

• Deep currents– Cold water sinks near the poles and flows

toward the equator.

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Fresh Water

• 2% of all of the water is fresh water• Most is locked in ice caps and glaciers• The remainder is found in lakes, rivers,

wetlands, soil, rock, and theatmosphere.

• River systems - network of streams thatdrains an area of land

Groundwater

• Groundwater - water that seeps into theground

• Less than 1% of all water on the Earth.• Aquifers - Rock layer that stores and

allows the flow of groundwater.• Recharge zone - surface of the land

where water enters the aquifer

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The Biosphere

• Biosphere - the narrow layer around theEarth’s surface where life can exist.

• 9km above the earth’s surface to the bottomof the ocean

• Life exists because– Liquid water– Moderate temperatures– Energy from the sun

Energy Flow in the Biosphere

• Closed system - energy enters theenvironment but matter does not

• Earth is a closed system for matter but anopen system for energy from the sun

• Plants make food from sun energy, animalseat the plants, animals eat animals.

• Energy is lost at each step in the food chain.– Activities of the organism– Heat