earth’s layered structure (ch. 8.4 in the text). earth’s internal structure layers based on...
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Earth’s Layered Structure (Ch. 8.4 in the Text)
Earth’s internal structure Earth’s internal structure
Layers based on composition • Crust
•Thin, rocky outer layer •Varies in thickness
•Oceanic crust: Roughly 7 km (5 miles) thick
•Continental crust: Averages 35–40 km (25 miles) thick
Layers based on composition • Crust
•Thin, rocky outer layer •Varies in thickness
•Oceanic crust: Roughly 7 km (5 miles) thick
•Continental crust: Averages 35–40 km (25 miles) thick
Earth’s layered structure Earth’s layered structure Discovering Earth’s major layers • Mohorovicic discontinuity (Moho)•Separates crust from underlying mantle
Discovering Earth’s major layers • Mohorovicic discontinuity (Moho)•Separates crust from underlying mantle
Earth’s internal structure Earth’s internal structure
Layers based on composition• Mantle
•Below crust to a depth of 2,890 kilometers (1,800 miles)
•Over 82% of Earth’s volume•Common rock type in the upper mantle is Peridotite
Layers based on composition• Mantle
•Below crust to a depth of 2,890 kilometers (1,800 miles)
•Over 82% of Earth’s volume•Common rock type in the upper mantle is Peridotite
Earth’s internal structure Earth’s internal structure Layers based on composition
• Core•Composed of an iron–nickel alloy •Average density of nearly 13 g/cm3
•Radius of 3,480 kilometers
Layers based on composition• Core
•Composed of an iron–nickel alloy •Average density of nearly 13 g/cm3
•Radius of 3,480 kilometers
Earth’s internal structure Earth’s internal structure
Layers based on physical properties• Lithosphere
•Crust and uppermost mantle •5 - 100 km thick•Cool, rigid, solid
• Asthenosphere•Beneath the lithosphere •Part of the Upper mantle•To a depth of about 660 km•Soft, weak layer that is easily deformed
Layers based on physical properties• Lithosphere
•Crust and uppermost mantle •5 - 100 km thick•Cool, rigid, solid
• Asthenosphere•Beneath the lithosphere •Part of the Upper mantle•To a depth of about 660 km•Soft, weak layer that is easily deformed
Earth’s internal structure Earth’s internal structure Layers based on physical properties• Lower Mantle
•2230 km thick•More rigid layer than the Asthenosphere•Rocks are very hot and capable of gradual flow
• Outer Core •Liquid layer •2,260 km (1,410 miles) thick•Convective flow of metallic iron within generates Earth’s magnetic field
Layers based on physical properties• Lower Mantle
•2230 km thick•More rigid layer than the Asthenosphere•Rocks are very hot and capable of gradual flow
• Outer Core •Liquid layer •2,260 km (1,410 miles) thick•Convective flow of metallic iron within generates Earth’s magnetic field
Earth’s internal structureEarth’s internal structure
Layers based on physical properties Inner Core
1220 km thickCompressed into a solid state by immense pressure
Layers based on physical properties Inner Core
1220 km thickCompressed into a solid state by immense pressure
Plate TectonicsCh. 9 (p. 246 - 277)
Plate TectonicsCh. 9 (p. 246 - 277)
Continental drift: an idea before its time Continental drift: an idea before its time
Alfred Wegener • First proposed hypothesis of Continental Drift in 1915
Continental drift hypothesis• Supercontinent called Pangaea began breaking apart about 200 million years ago
• Continents “drifted” to present positions
Alfred Wegener • First proposed hypothesis of Continental Drift in 1915
Continental drift hypothesis• Supercontinent called Pangaea began breaking apart about 200 million years ago
• Continents “drifted” to present positions
Pangaea approximately 200 million years ago
Pangaea approximately 200 million years ago
Continental drift: an idea before its time Continental drift: an idea before its time
Wegener’s continental drift hypothesis• Evidence used by Wegener
•Fit of South America and Africa •Fossils match across the seas•Rock types and structures match •Ancient climates
• Problem with Wegener’s Hypothesis: What force was moving the continents?
Wegener’s continental drift hypothesis• Evidence used by Wegener
•Fit of South America and Africa •Fossils match across the seas•Rock types and structures match •Ancient climates
• Problem with Wegener’s Hypothesis: What force was moving the continents?
Similar mountain ranges
on different continents
Similar mountain ranges
on different continents
Paleoclimatic evidence
for continental drift
Paleoclimatic evidence
for continental drift
Plate Tectonics: the new paradigm Plate Tectonics: the new paradigm
The Theory of Plate TectonicsWe are now able to measure the movement of the continents due to technological advancements
Associated with Earth’s rigid outer shell • Called the lithosphere • Consists of several plates
•Largest plate is the Pacific plate
The Theory of Plate TectonicsWe are now able to measure the movement of the continents due to technological advancements
Associated with Earth’s rigid outer shell • Called the lithosphere • Consists of several plates
•Largest plate is the Pacific plate
Plate tectonics: the new paradigm Plate tectonics: the new paradigm Asthenosphere
• Exists beneath the lithosphere • Hotter and weaker (fluid like) than lithosphere
• Allows for motion of lithosphere Plate boundaries
• All major interactions among plates occur along their boundaries
Asthenosphere • Exists beneath the lithosphere • Hotter and weaker (fluid like) than lithosphere
• Allows for motion of lithosphere Plate boundaries
• All major interactions among plates occur along their boundaries
Plate tectonics: the new paradigm Plate tectonics: the new paradigm
Plate boundaries • Types of plate boundaries
•Divergent plate boundaries (Constructive margins)•Two plates move apart•Mid Ocean ridges and seafloor spreading
•Oceanic ridges develop along well-developed boundaries
•Along ridges, seafloor spreading creates new seafloor
Plate boundaries • Types of plate boundaries
•Divergent plate boundaries (Constructive margins)•Two plates move apart•Mid Ocean ridges and seafloor spreading
•Oceanic ridges develop along well-developed boundaries
•Along ridges, seafloor spreading creates new seafloor
Divergent boundaries are located along oceanic ridges
Divergent boundaries are located along oceanic ridges
The East African rift – a divergent boundary on land
The East African rift – a divergent boundary on land
Plate tectonics: the new paradigm Plate tectonics: the new paradigm
Plate boundaries •Convergent plate boundaries (destructive margins)•Plates collide, an ocean trench forms, and lithosphere is subducted into the mantle
Plate boundaries •Convergent plate boundaries (destructive margins)•Plates collide, an ocean trench forms, and lithosphere is subducted into the mantle
Plate tectonics: the new paradigm Plate tectonics: the new paradigm
Plate boundaries • Types of plate boundaries
•Convergent plate boundaries (destructive margins)•Oceanic–continental convergence
•Denser oceanic slab sinks into the asthenosphere
•Pockets of magma develop and rise •Continental volcanic arc forms•Examples include the Andes, Cascades, and the Sierra Nevadan system
Plate boundaries • Types of plate boundaries
•Convergent plate boundaries (destructive margins)•Oceanic–continental convergence
•Denser oceanic slab sinks into the asthenosphere
•Pockets of magma develop and rise •Continental volcanic arc forms•Examples include the Andes, Cascades, and the Sierra Nevadan system
An oceanic–continental convergent plate boundary
An oceanic–continental convergent plate boundary
Plate tectonics: the new paradigm Plate tectonics: the new paradigm
Plate boundaries • Types of plate boundaries
•Convergent plate boundaries (destructive margins)•Oceanic–oceanic convergence
•Two oceanic slabs converge and one descends beneath the other
•Often forms volcanoes on the ocean floor
•Volcanic island arc forms as volcanoes emerge from the sea
•Examples include the Aleutian, and Mariana.
Plate boundaries • Types of plate boundaries
•Convergent plate boundaries (destructive margins)•Oceanic–oceanic convergence
•Two oceanic slabs converge and one descends beneath the other
•Often forms volcanoes on the ocean floor
•Volcanic island arc forms as volcanoes emerge from the sea
•Examples include the Aleutian, and Mariana.
An oceanic–oceanic convergent plate boundary
An oceanic–oceanic convergent plate boundary
Plate tectonics: the new paradigm Plate tectonics: the new paradigm
Plate boundaries • Types of plate boundaries
•Convergent plate boundaries (destructive margins)•Continental–continental convergence
•When subducting plates contain continental material, two continents collide
•Can produce new mountain ranges such as the Himalayas
Plate boundaries • Types of plate boundaries
•Convergent plate boundaries (destructive margins)•Continental–continental convergence
•When subducting plates contain continental material, two continents collide
•Can produce new mountain ranges such as the Himalayas
A continental–continental convergent plate boundary
A continental–continental convergent plate boundary
The collision of India and Asia produced the Himalayas
The collision of India and Asia produced the Himalayas
The collision of India and Asia produced the Himalayas
The collision of India and Asia produced the Himalayas
Plate tectonics: the new paradigm Plate tectonics: the new paradigm
Plate boundaries • Types of plate boundaries
•Transform fault boundaries •Plates slide past one another
•No new crust is created or destroyed
Plate boundaries • Types of plate boundaries
•Transform fault boundaries •Plates slide past one another
•No new crust is created or destroyed
Testing the plate tectonics modelTesting the plate tectonics model
Evidence from ocean drilling• Some of the most convincing evidence confirming seafloor spreading has come from drilling directly into ocean-floor sediment•Age of sediments•Thickness of ocean-floor sediments verifies seafloor spreading
Evidence from ocean drilling• Some of the most convincing evidence confirming seafloor spreading has come from drilling directly into ocean-floor sediment•Age of sediments•Thickness of ocean-floor sediments verifies seafloor spreading
Testing the plate tectonics modelTesting the plate tectonics model
Hot spots and Mantle Plumes•Caused by rising plumes of mantle material
•Volcanoes can form over them (Hawaiian Island chain)
Hot spots and Mantle Plumes•Caused by rising plumes of mantle material
•Volcanoes can form over them (Hawaiian Island chain)
The Hawaiian Islands have formed over a hot spot
The Hawaiian Islands have formed over a hot spot
Testing the plate tectonics model Testing the plate tectonics model
Evidence for the plate tectonics model • Paleomagnetism
•Probably the most persuasive evidence •Ancient magnetism preserved in rocks •Paleomagnetic records show
•Polar wandering (evidence that continents moved)
Evidence for the plate tectonics model • Paleomagnetism
•Probably the most persuasive evidence •Ancient magnetism preserved in rocks •Paleomagnetic records show
•Polar wandering (evidence that continents moved)
Measuring plate motion Measuring plate motion
Measuring plate motion• By using hot spot “tracks” like those of the Hawaiian Island chain
• Using space-age technology to directly measure the relative motion of plates •Global Positioning System (GPS)
Measuring plate motion• By using hot spot “tracks” like those of the Hawaiian Island chain
• Using space-age technology to directly measure the relative motion of plates •Global Positioning System (GPS)
Directions and rates of plate motionsDirections and rates of plate motions
What drives plate motion What drives plate motion Driving mechanism of plate tectonics • Earth’s heat is the driving force
•Convective Currents
Driving mechanism of plate tectonics • Earth’s heat is the driving force
•Convective Currents
Mantle Convection Mantle Convection
Layering at 660 kmLayering at 660 km
Plate Motion at the SurfacePlate Motion at the Surface
A possible view of the world 50 million years from now
A possible view of the world 50 million years from now