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Chapter 3 – The Dynamic EarthSection 1: The Geosphere
1. Describe the composition & structure of the Earth
2. Describe the Earth’s tectonic plates3. Explain the main cause of earthquakes & their
effects4. Identify the relationship between volcanic
eruptions & climate change5. Describe how wind & water alter the Earth’s
surface
The Earth as a System
• Earth consists of rock, air, water, & living things that interact with each other
• Divided into 4 parts:WATER
LIVING THINGS
ROCK
AIR
The Earth as a System• Geosphere– Solid portion consisting of rock– Extends from center of core to surface of crust
• Atmosphere– Mixture of gases– Most found in first 30 km above Earth’s surface
• Hydroshpere– All water on or near surface– Most is oceans
• Biosphere – Where life exists– Extends from 9 km above surface to bottom of ocean
Discovering Earth’s Interior• Seismic waves used
to study interior of Earth
• Seismic waves– Travel through
Earth’s interior during earthquakes
– Altered by type of material they move
– Changes in speed & direction measured when passing through different layers
Earthquake
Seismic wave
Composition of the Earth
• Divided into three layers based on composition – Crust– Mantle – Core
• layers become progressively denser toward the center
Crust
Mantle
Core
Crust• Thin, outermost layer – 5 to 8 km beneath oceans– 20 to 70 km beneath
continents
• Solid, brittle • Composed of lightweight
elements• Makes up less that 1% of
Earth’s mass
Mantle• Layer between crust &
core• Composed of rock with
medium density• Contains iron-rich
minerals• Makes up 64% of
Earth’s mass• Approximately 2900 km
thick
Core• Innermost layer– Liquid outer core• Super-heated molten lava• Composed of liquid nickel
& iron– Solid inner core• Sphere of solid nickel &
iron
• Consists of densest elements
• Radius approximately 3400 km
Solid inner core
The Structure of the Earth
• Divided into 5 layers based on the physical properties
Lithosphere
Asthenosphere
Mesosphere
Outer CoreInner Core
Lithosphere• Composes crust &
upper part of mantle
– 15-300 km thick (9-185 mi)
• Divided into large pieces called tectonic plates– May be oceanic or
continental– Slide on fluid portion
of mantle– Movement can cause
earthquakes
Asthenosphere
• Beneath lithosphere– 250 km thick (150 mi)
• Solid, plastic-like material of mantle– Made of rock that
flows– Due to temperature &
pressure• Allows for movement
of tectonic plates
Mesophere
• Lower part of mantle
• More solid & rigid than asthenosphere due to increased pressure – Can’t flow
Lithosphere
Asthenosphere
Mesosphere
Outer CoreInner Core
Outer Core• Super-heated molten
lava– Composed of liquid nickel
& iron– 4000 to 9000 °F
• Source of Earth’s magnetic field– Creates protective bubble– Deflects Sun’s solar winds
Inner Core
• Solid ball• Composed of nickel
& iron• 9000 °F &
45,000,000 psi• Rotates in liquid
outer core
Plate Tectonics
• Large, irregularly shaped slabs of rock• Composed of oceanic & continental
lithosphere– Continental rocks• Lightweight minerals (quartz, feldspar)• Thicker crust
– Oceanic rocks• Heavier, denser basltic rocks• Thinner crust
Major & Minor Tectonic Plates
Plates move in different directions and speeds, thus crash together, pull apart or side swipe each other like cars in a demolition derby
Plate Boundaries• Most geologic activity occurs where plates meet or
divide (called boundaries)• Movement of plates creates 3 types of tectonic
boundaries– Convergent – plates collide, move into one another– Divergent – plates move apart– Transform – plates move sideways in relation to one
another• Movement of tectonic plates causes– Mountain formation– Earthquakes– Volcanic eruptions
Plate Tectonics and Mountain Formation
• Plates collide, crust thickens
• Rocks break & buckle– Continental plate folds
into huge mountain – Oceanic plate forms
trench• Examples– Rocky mountains (N.
America)– Himalaya mountains
(Central Asia
Earthquakes• Faults – breaks in Earth’s
crust where plates slide past each other
• Rocks under stress break off triggering ground vibrations - called earthquakes
• Magnitude (Richter Scale)– Measure of energy released– 2.0 – smallest felt– 9.5 – largest recorded– Increase of 1 whole number
= 31.7 times more energy
Where Earthquakes Occur
Most occur at or near plate boundaries
Earthquake Hazard• Earthquake hazard level determined by past &
present seismic activity• Hazards (effects) include– Ground shaking (building damage/settling of ground
beneath to different level)– Ground displacement – Flooding (breakage of levies, dams, Tsunamis)– Fire (broken gas & power lines)
• Human hazards due to man-made structures– Being crushed, buried or burned or drowning
• National Hazards Maps used by cities, counties & local governments to update & create more stringent building codes
Volcanoes• Mountains built from
magma (molten rock)• Magma rises to
surface from interior• Most common at
convergent or divergent plate boundaries
• Can occur on land or in oceans
Block between separating faults cracks, drops into asthenosphere forming a rift. Magma seeps upward to fill in crack
Volcanoes: The Ring of Fire
• Majority of active volcanoes on land located along tectonic plate surrounding the Pacific Ocean
Pacific Plate
North American PlateEurasian Plate
Antarctic Plate
South American Plate
Australian Plate
Local Effects of Volcanic Eruptions
• Clouds of hot ash, dust, & gases flow down the slopes of volcanoes searing anything in its path– Obscures sunlight, killing plants & animals
• Volcanic ash mixes with water producing mudflows– Water contamination– Land contamination
• Collapse of buildings, burying of crops, & damage to vehicle engines due to falling ash
Global Effects of Volcanic Eruptions
• Can cause changes in Earth’s climate• Ash & sulfur-rich gases reach upper
atmosphere & reduce sunlight reaching Earth’s surface
• Reduction in sunlight reduces average global temperatures
Erosion• Process resulting in materials of the Earth’s surface
being loosened, dissolved or worn away & transported from one place to another by natural agents such as wind, water, ice or gravity
• Water erosion– Rivers carve deep canyons or gorges into bedrock– Depositing of dust, pebbles, rocks forms new land areas– Oceans erode coastlines
• Wind erosion– Removal of most fertile part of soil lowering soil
productivity– Creates sand dunes