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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 travel
through the interior of the earth during
an earthquake.
• Seismic waves are used in order to
determine 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 of
each layer
• Made up of three layers that get progressively
denser
• 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 layers
based on the physical properties of each
layer.
• 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 of
geologic activity
– Mountains form
– Earthquakes occur
– Volcanoes erupt
Plate Tectonics and Mountain
Building
• Plates colliding
causes the formation
of mountains
• Example-Himalayas
formed from the
collision of the Asian
and 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 an
earthquake.
• Smallest magnitude - 2.0
• Largest magnitude - 9.5
• Each magnitude is 31.7 times
more energy than the number
below it.
• Example - a magnitude of 6
releases 31.7 times more energy
than a magnitude of 5
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Volcanoes
• Volcano - mountain built from magma
that rises form the Earth’s interior to the
surface
• 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 volcanoes
erupt and dead animals and plants decay.
• Oxygen makes up 21% of the gases
– Primarily produced by plants
Air Pressure
• Gravity pulls the atmosphere towards
the Earth’s surface
• The atmosphere is 30km from the
ground
• The atmosphere is denser near the
Earth’s surface
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Layers of the Atmosphere
• Layers of the atmosphere based on
temperature 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 the
ozone.
– Ozone - Absorbs ultraviolet readiation
which 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 in
contact 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 billionths
of the energy from the sun
• The energy which does reach the earth is
tremendous
• About half of the solar energy reaches the
surface of the Earth
• The rest of the energy is absorbed or
reflected by clouds, gases, dust or the earth’s
surface.
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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 greenhouse
gases.
• Greenhouse Effect - Gases trap heat near the
surface 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 of
the water on or near
the Earth’s surface
• Water cycle - the
movement of water
into the air, onto
land and then back
to the water.
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Hydropshere and the Water Cycle
• Evaporation - liquid water is heated by
the sun and then rises into the
atmosphere as water vapor
• Condensation - water vapor forms water
droplets
• Precipitation - large water droplets
which fall from the clouds.
Earth’s Oceans
• World ocean - single, large interconnected
body 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 over
50% of heat from the sun
• Absorbs and releases heat more slowly
than the land
• Regulates the temperature of the
atmosphere
• Ocean currents transports heat around
the globe
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Ocean Currents
• Currents - movement of water that
occur at or near the ocean surface.
• Currents are driven by global wind
patterns
• Currents influence the climate of the
land 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 the
atmosphere.
• River systems - network of streams that
drains an area of land
Groundwater
• Groundwater - water that seeps into the
ground
• 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 the
Earth’s surface where life can exist.
• 9km above the earth’s surface to the bottom
of the ocean
• Life exists because
– Liquid water
– Moderate temperatures
– Energy from the sun
Energy Flow in the Biosphere
• Closed system - energy enters the
environment but matter does not
• Earth is a closed system for matter but an
open system for energy from the sun
• Plants make food from sun energy, animals
eat the plants, animals eat animals.
• Energy is lost at each step in the food chain.
– Activities of the organism
– Heat
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