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Transcript of Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1.Describe the composition & structure of...
![Page 1: Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1.Describe the composition & structure of the Earth 2.Describe the Earth’s tectonic plates 3.Explain.](https://reader035.fdocuments.net/reader035/viewer/2022062516/56649e225503460f94b0fb9f/html5/thumbnails/1.jpg)
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
![Page 2: Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1.Describe the composition & structure of the Earth 2.Describe the Earth’s tectonic plates 3.Explain.](https://reader035.fdocuments.net/reader035/viewer/2022062516/56649e225503460f94b0fb9f/html5/thumbnails/2.jpg)
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
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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
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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
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Composition of the Earth
• Divided into three layers based on composition – Crust– Mantle – Core
• layers become progressively denser toward the center
Crust
Mantle
Core
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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
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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
![Page 8: Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1.Describe the composition & structure of the Earth 2.Describe the Earth’s tectonic plates 3.Explain.](https://reader035.fdocuments.net/reader035/viewer/2022062516/56649e225503460f94b0fb9f/html5/thumbnails/8.jpg)
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
![Page 9: Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1.Describe the composition & structure of the Earth 2.Describe the Earth’s tectonic plates 3.Explain.](https://reader035.fdocuments.net/reader035/viewer/2022062516/56649e225503460f94b0fb9f/html5/thumbnails/9.jpg)
The Structure of the Earth
• Divided into 5 layers based on the physical properties
Lithosphere
Asthenosphere
Mesosphere
Outer CoreInner Core
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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
![Page 11: Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1.Describe the composition & structure of the Earth 2.Describe the Earth’s tectonic plates 3.Explain.](https://reader035.fdocuments.net/reader035/viewer/2022062516/56649e225503460f94b0fb9f/html5/thumbnails/11.jpg)
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
![Page 12: Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1.Describe the composition & structure of the Earth 2.Describe the Earth’s tectonic plates 3.Explain.](https://reader035.fdocuments.net/reader035/viewer/2022062516/56649e225503460f94b0fb9f/html5/thumbnails/12.jpg)
Mesophere
• Lower part of mantle
• More solid & rigid than asthenosphere due to increased pressure – Can’t flow
Lithosphere
Asthenosphere
Mesosphere
Outer CoreInner Core
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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
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Inner Core
• Solid ball• Composed of nickel
& iron• 9000 °F &
45,000,000 psi• Rotates in liquid
outer core
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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
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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
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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
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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
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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
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Where Earthquakes Occur
Most occur at or near plate boundaries
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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
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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
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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
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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
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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
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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