Plate tectonics
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The document discusses the theory of plate tectonics. It explains that the Earth's crust and upper mantle are broken into plates that move around on top of the mantle. Plates interact at boundaries where they diverge (move apart), converge (move together), or slide past one another. Convection currents in the mantle provide the driving force for plate tectonics.
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Divergent plate boundaries
Divergent plate boundaries occur where tectonic plates are moving away from each other. There are two main types of tectonic plates - continental plates composed of rocks and minerals, and oceanic plates which are thinner and located under seas. As the plates separate, molten lava rises up between them to form new crust. This divergence is driven by convection currents in the Earth's mantle which push the plates apart. New crust forms underwater as seafloor spreading, and volcanoes and mountains can form on the edges of the separating plates.
Plate tectonics
The document discusses the theory of plate tectonics. [1] The Earth's crust and upper mantle are broken into sections called plates that move around on top of the mantle. [2] The lithosphere comprises the crust and part of the upper mantle and "floats" on the asthenosphere, which is the plastic layer below. [3] There are two types of plates - ocean plates below oceans and continental plates below continents.
Continental drift theory and seafloor spreading
The document discusses continental drift theory and seafloor spreading. Continental drift theory states that the continents were once joined together in a supercontinent called Pangaea before drifting apart. Evidence for this includes matching fossil and rock formations, as well as coal deposits. Seafloor spreading theory developed by Harry Hess and Robert Dietz proposes that new ocean crust is formed at mid-ocean ridges as the continents separate. Evidence includes the age of ocean rocks decreasing with distance from ridges and magnetic reversals in ocean crust.
Sea-Floor Spreading
1. The document discusses sea-floor spreading, which is the process where new oceanic crust forms at mid-ocean ridges as tectonic plates move away from each other.
2. Evidence that supports sea-floor spreading includes magnetic stripe patterns in the ocean floor and samples from ocean crust that show it is younger near ridges and older further away.
3. Oceanic crust is basaltic rock that forms at ridges and is then recycled in subduction zones, making it generally younger than continental crust which does not undergo this recycling process.
Plate Boundaries
The document describes the four main types of plate boundaries:
1) Divergent boundaries occur at spreading centers where new crust is created and plates move apart, such as at the Mid-Atlantic Ridge.
2) Convergent boundaries exist where plates collide and one is subducted under the other, forming deep ocean trenches.
3) Transform boundaries result from two plates sliding past each other horizontally, such as along the San Andreas Fault.
4) Continent-continent collisions buckle and uplift massive mountain ranges, as when India collided with Asia to form the Himalayas.
Sea floor spreading
Scientists in the 1950s used sonar to map the mid-ocean ridge and discovered it was not flat but contained underwater mountains. This discovery led them to research what the ridge was and how it formed. Evidence from molten rock samples, magnetic stripes in the ocean crust, and the ages of rocks drilled from the ocean floor supported Harry Hess' theory from 1960 of sea-floor spreading, where new crust forms at mid-ocean ridges and spreads outward over time.
Grade 10 _Plate Tectonics2_Science10.ppt
The document discusses the theory of plate tectonics, including what plates are, how they move, and the three types of plate boundaries. The three types of boundaries are divergent boundaries, where plates move apart; convergent boundaries, where plates move towards each other; and transform boundaries, where plates move past each other laterally. Each boundary type results in different geologic features and events due to the stresses caused by the ways plates are pulled, pushed, or sheared at their edges.
Plate boundaries
There are three main types of plate boundaries: 1) transform boundaries where plates slide horizontally past one another like the San Andreas Fault, 2) convergent boundaries where plates collide and one is subducted beneath the other in oceanic trenches or mountain building, and 3) divergent boundaries where plates spread apart like mid-ocean ridges and new crust is formed through volcanic activity.
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Divergent plate boundaries
Divergent plate boundaries occur where tectonic plates are moving away from each other. There are two main types of tectonic plates - continental plates composed of rocks and minerals, and oceanic plates which are thinner and located under seas. As the plates separate, molten lava rises up between them to form new crust. This divergence is driven by convection currents in the Earth's mantle which push the plates apart. New crust forms underwater as seafloor spreading, and volcanoes and mountains can form on the edges of the separating plates.
Plate tectonics
The document discusses the theory of plate tectonics. [1] The Earth's crust and upper mantle are broken into sections called plates that move around on top of the mantle. [2] The lithosphere comprises the crust and part of the upper mantle and "floats" on the asthenosphere, which is the plastic layer below. [3] There are two types of plates - ocean plates below oceans and continental plates below continents.
Continental drift theory and seafloor spreading
The document discusses continental drift theory and seafloor spreading. Continental drift theory states that the continents were once joined together in a supercontinent called Pangaea before drifting apart. Evidence for this includes matching fossil and rock formations, as well as coal deposits. Seafloor spreading theory developed by Harry Hess and Robert Dietz proposes that new ocean crust is formed at mid-ocean ridges as the continents separate. Evidence includes the age of ocean rocks decreasing with distance from ridges and magnetic reversals in ocean crust.
Sea-Floor Spreading
1. The document discusses sea-floor spreading, which is the process where new oceanic crust forms at mid-ocean ridges as tectonic plates move away from each other.
2. Evidence that supports sea-floor spreading includes magnetic stripe patterns in the ocean floor and samples from ocean crust that show it is younger near ridges and older further away.
3. Oceanic crust is basaltic rock that forms at ridges and is then recycled in subduction zones, making it generally younger than continental crust which does not undergo this recycling process.
Plate Boundaries
The document describes the four main types of plate boundaries:
1) Divergent boundaries occur at spreading centers where new crust is created and plates move apart, such as at the Mid-Atlantic Ridge.
2) Convergent boundaries exist where plates collide and one is subducted under the other, forming deep ocean trenches.
3) Transform boundaries result from two plates sliding past each other horizontally, such as along the San Andreas Fault.
4) Continent-continent collisions buckle and uplift massive mountain ranges, as when India collided with Asia to form the Himalayas.
Sea floor spreading
Scientists in the 1950s used sonar to map the mid-ocean ridge and discovered it was not flat but contained underwater mountains. This discovery led them to research what the ridge was and how it formed. Evidence from molten rock samples, magnetic stripes in the ocean crust, and the ages of rocks drilled from the ocean floor supported Harry Hess' theory from 1960 of sea-floor spreading, where new crust forms at mid-ocean ridges and spreads outward over time.
Grade 10 _Plate Tectonics2_Science10.ppt
The document discusses the theory of plate tectonics, including what plates are, how they move, and the three types of plate boundaries. The three types of boundaries are divergent boundaries, where plates move apart; convergent boundaries, where plates move towards each other; and transform boundaries, where plates move past each other laterally. Each boundary type results in different geologic features and events due to the stresses caused by the ways plates are pulled, pushed, or sheared at their edges.
Plate boundaries
There are three main types of plate boundaries: 1) transform boundaries where plates slide horizontally past one another like the San Andreas Fault, 2) convergent boundaries where plates collide and one is subducted beneath the other in oceanic trenches or mountain building, and 3) divergent boundaries where plates spread apart like mid-ocean ridges and new crust is formed through volcanic activity.
Divergent boundary
Divergent plate boundaries occur when tectonic plates pull apart from each other. Rising convection currents in the mantle push up on lithospheric plates, stretching and thinning the crust until it breaks along parallel faults tilted outward. This forms mid-ocean ridges or rift valleys on land. As the plates continue diverging, new crust is formed by magma rising through the cracks from the asthenosphere. Examples of divergent boundaries include the East Africa rift and Rio Grande rift.
Continental drift and seafloor spreading
The document discusses continental drift and plate tectonics. It explains that continental drift was first proposed in the 16th century and was further developed and advocated for by Alfred Wegener in the early 20th century. Wegener proposed that the continents were once joined together in a supercontinent called Pangaea, which began breaking apart about 200 million years ago. The theory of plate tectonics posits that the Earth's crust is broken into plates that move over time, interacting through processes like seafloor spreading at mid-ocean ridges, subduction at convergent boundaries, and lateral movement at transform boundaries.
Stress in the earth’s crust
This document discusses different types of stresses that cause rock deformation, including confining stress, compression stress, tension stress, and shear stress. It also describes different types of resulting rock features such as folds, fractures, faults, and mountains. Specifically, it compares three types of folds - monoclines, anticlines, and synclines. It also differentiates between three main types of plate boundaries: divergent boundaries which cause tension stress and normal faults, convergent boundaries which cause compression stress and reverse faults, and transform boundaries which cause shear stress and strike-slip faults. Mountains can form at convergent plate boundaries through folding and faulting of rocks.
Mass wasting processes
Gravity pulls the rocks, soils and debris on a downward slope, naturally, without any chemical change. This downward movement is called as mass -movement or mass-wasting.
Landslides, mudflows and rockfalls are all belonging to this category of geomorphic processes.
Mass-wasting may lead to severe natural disasters by affecting the life and building structures in different places. Understanding of mass-wasting will certainly help to mitigate the impacts of these hazards and plan the development activities.
Plate Tectonics Notes
- The Earth's crust is made up of tectonic plates that are constantly moving due to convection currents in the mantle.
- There are three types of plate boundaries: divergent where plates separate and new crust is formed, convergent where plates collide and oceanic plates are subducted, and transform where plates slide past each other.
- Evidence for plate tectonics includes magnetic patterns in ocean crust, matching fossils and rock formations on separated continents, and the fit of continental shelves. Plate movements have caused continents like Pangaea to break apart over millions of years.
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This document provides information about plate tectonics and earthquakes. It defines key terms related to plate tectonics like continental drift, plates, mantle convection, and plate boundaries. It describes the three main types of plate boundaries: convergent where plates push together, divergent where they pull apart, and transform where they slide past each other. Evidence for plate tectonics includes matching continents, matching fossils, magnetic reversals in ocean floors, and crustal deformations. The document also defines earthquake terms and describes how seismic waves are used to determine the location and size of quakes.
Study of plate tectonics of the earth, or plate movement,
a) Wegener’s Evidence (Continental Drift)
b) History of Plate Tectonics
c) Breakup and Appearence of Pangea
WHAT IS A PLATE?
Major continental and oceanic plates include:
Types of Earth’s Crust:
Plate tectonics (from the Late Latin tectonicus) is a scientific theory which describes the large scale motions of Earth's lithosphere.
THE DYNAMIC EARTH:
The earth is a dynamic planet, continuously changing both externally and internally. The earth’s surface is constantly being changed by endo-genetic processes resulting in volcanism and tectonism, and exogenetic processes such as erosion and deposition. These processes have been active throughout geological history. The processes that change the surface feature are normally very slow (erosion and deposition) except some catastrophic changes that occur instantaneously as in the case of volcanism or earthquakes. The interior of the earth is also in motion. Deeper inside the earth, the liquid core probably flows at a geologically rapid rate of a few tenths of mm/s. Several hypotheses attempted to explain the dynamism of the earth.
+ Horizontal movement hypothesis
+ Continental drift, displacement hypothesis
Development of the plate tectonic theory.
Plate tectonic theory arose out of the hypothesis of continental drift proposed by Alfred Wegener in 1912. He suggested that the present continents once formed a single land mass that drifted apart, thus releasing the continents from the Earth's core and likening them to "icebergs" of low density granite floating on a sea of denser basalt.
Seafloor Spreading
The first evidence that the lithospheric plates did move came with the discovery of variable magnetic field direction in rocks of differing ages.
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Convergent plate boundaries occur where tectonic plates move towards one another. There are three main types:
1) Oceanic-oceanic, where two oceanic plates collide and one subducts under the other, forming ocean trenches.
2) Oceanic-continental, where an oceanic plate subducts under a continental plate, pushing up mountains.
3) Continental-continental, where collision resists subduction and the plates break and fold, forming mountains.
Seafloor spreading theory discuss 3
1. Harry Hess proposed the theory of seafloor spreading in 1962, which provided evidence that Wegener's theory of continental drift was correct. Hess theorized that new ocean crust is formed at mid-ocean ridges through volcanic eruptions and then spreads outwards, pushing older crust farther away.
2. Evidence for seafloor spreading includes rock formations only possible from cooled lava, magnetic stripe patterns in ocean crust recording reversals of Earth's magnetic field, and drilling samples showing younger rock nearer to ridges.
3. Seafloor spreading is driven by convection currents in the Earth's mantle; subduction zones allow parts of ocean crust to sink back into the mantle and regulate ocean size.
Sea Floor Spreading
New evidence supported the theory of sea floor spreading and plate tectonics. Mapping of the seafloor using sonar revealed a mid-ocean ridge running through the Atlantic Ocean. Rocks near the ridge are younger, becoming progressively older further from the ridge, showing new crust is generated at the ridge through sea floor spreading. While new crust is created at ridges, older oceanic crust is recycled back into the Earth through subduction at plate boundaries, keeping the size of the Earth stable over time. This evidence of sea floor spreading supported Wegener's theory of continental drift.
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The document discusses three types of plate boundaries:
1) Divergent boundaries, where plates pull apart and new crust is formed, examples include mid-ocean ridges and continental rift valleys.
2) Convergent boundaries, where plates push together, examples include oceanic-continental collisions which form volcanoes and trenches, and oceanic-oceanic collisions which form island arcs.
3) Transform boundaries, where plates slide horizontally past one another along transform faults.
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The theory of plate tectonics describes how the Earth's crust is broken into plates that move around on the mantle. The lithosphere consists of the crust and rigid upper mantle, while the asthenosphere below is plastic and allows the plates to move. There are two types of plates - oceanic and continental. Plates interact at boundaries, including divergent boundaries where new crust is formed, convergent boundaries where plates collide and form features like volcanoes, and transform boundaries where plates slide past each other. Plate movement is caused by convection currents in the underlying mantle.
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The document discusses continental drift and plate tectonics. It explains that continental drift was first proposed in the 16th century and was further developed and advocated for by Alfred Wegener in the early 20th century. Wegener proposed that the continents were once joined together in a supercontinent called Pangaea, which began breaking apart about 200 million years ago. The theory of plate tectonics posits that the Earth's crust is broken into plates that move over time, interacting through processes like seafloor spreading at mid-ocean ridges, subduction at convergent boundaries, and lateral movement at transform boundaries.
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This document discusses different types of stresses that cause rock deformation, including confining stress, compression stress, tension stress, and shear stress. It also describes different types of resulting rock features such as folds, fractures, faults, and mountains. Specifically, it compares three types of folds - monoclines, anticlines, and synclines. It also differentiates between three main types of plate boundaries: divergent boundaries which cause tension stress and normal faults, convergent boundaries which cause compression stress and reverse faults, and transform boundaries which cause shear stress and strike-slip faults. Mountains can form at convergent plate boundaries through folding and faulting of rocks.
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Gravity pulls the rocks, soils and debris on a downward slope, naturally, without any chemical change. This downward movement is called as mass -movement or mass-wasting.
Landslides, mudflows and rockfalls are all belonging to this category of geomorphic processes.
Mass-wasting may lead to severe natural disasters by affecting the life and building structures in different places. Understanding of mass-wasting will certainly help to mitigate the impacts of these hazards and plan the development activities.
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- The Earth's crust is made up of tectonic plates that are constantly moving due to convection currents in the mantle.
- There are three types of plate boundaries: divergent where plates separate and new crust is formed, convergent where plates collide and oceanic plates are subducted, and transform where plates slide past each other.
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Study of plate tectonics of the earth, or plate movement,
a) Wegener’s Evidence (Continental Drift)
b) History of Plate Tectonics
c) Breakup and Appearence of Pangea
WHAT IS A PLATE?
Major continental and oceanic plates include:
Types of Earth’s Crust:
Plate tectonics (from the Late Latin tectonicus) is a scientific theory which describes the large scale motions of Earth's lithosphere.
THE DYNAMIC EARTH:
The earth is a dynamic planet, continuously changing both externally and internally. The earth’s surface is constantly being changed by endo-genetic processes resulting in volcanism and tectonism, and exogenetic processes such as erosion and deposition. These processes have been active throughout geological history. The processes that change the surface feature are normally very slow (erosion and deposition) except some catastrophic changes that occur instantaneously as in the case of volcanism or earthquakes. The interior of the earth is also in motion. Deeper inside the earth, the liquid core probably flows at a geologically rapid rate of a few tenths of mm/s. Several hypotheses attempted to explain the dynamism of the earth.
+ Horizontal movement hypothesis
+ Continental drift, displacement hypothesis
Development of the plate tectonic theory.
Plate tectonic theory arose out of the hypothesis of continental drift proposed by Alfred Wegener in 1912. He suggested that the present continents once formed a single land mass that drifted apart, thus releasing the continents from the Earth's core and likening them to "icebergs" of low density granite floating on a sea of denser basalt.
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Convergent boundaries
Convergent plate boundaries occur where tectonic plates move towards one another. There are three main types:
1) Oceanic-oceanic, where two oceanic plates collide and one subducts under the other, forming ocean trenches.
2) Oceanic-continental, where an oceanic plate subducts under a continental plate, pushing up mountains.
3) Continental-continental, where collision resists subduction and the plates break and fold, forming mountains.
Seafloor spreading theory discuss 3
1. Harry Hess proposed the theory of seafloor spreading in 1962, which provided evidence that Wegener's theory of continental drift was correct. Hess theorized that new ocean crust is formed at mid-ocean ridges through volcanic eruptions and then spreads outwards, pushing older crust farther away.
2. Evidence for seafloor spreading includes rock formations only possible from cooled lava, magnetic stripe patterns in ocean crust recording reversals of Earth's magnetic field, and drilling samples showing younger rock nearer to ridges.
3. Seafloor spreading is driven by convection currents in the Earth's mantle; subduction zones allow parts of ocean crust to sink back into the mantle and regulate ocean size.
Sea Floor Spreading
New evidence supported the theory of sea floor spreading and plate tectonics. Mapping of the seafloor using sonar revealed a mid-ocean ridge running through the Atlantic Ocean. Rocks near the ridge are younger, becoming progressively older further from the ridge, showing new crust is generated at the ridge through sea floor spreading. While new crust is created at ridges, older oceanic crust is recycled back into the Earth through subduction at plate boundaries, keeping the size of the Earth stable over time. This evidence of sea floor spreading supported Wegener's theory of continental drift.
2.4 tectonic plate boundaries
The document discusses three types of plate boundaries:
1) Divergent boundaries, where plates pull apart and new crust is formed, examples include mid-ocean ridges and continental rift valleys.
2) Convergent boundaries, where plates push together, examples include oceanic-continental collisions which form volcanoes and trenches, and oceanic-oceanic collisions which form island arcs.
3) Transform boundaries, where plates slide horizontally past one another along transform faults.
Plate Tectonics
The theory of plate tectonics describes how the Earth's crust is broken into plates that move around on the mantle. The lithosphere consists of the crust and rigid upper mantle, while the asthenosphere below is plastic and allows the plates to move. There are two types of plates - oceanic and continental. Plates interact at boundaries, including divergent boundaries where new crust is formed, convergent boundaries where plates collide and form features like volcanoes, and transform boundaries where plates slide past each other. Plate movement is caused by convection currents in the underlying mantle.
Endogenic and exogenic processes
The document discusses endogenic and exogenic geological processes. Endogenic processes occur beneath the Earth's surface and include folding, faulting, volcanism, metamorphism, and earthquakes. They shape geological structures and form important mineral resources. Exogenic processes happen on the surface and include weathering, erosion, mass wasting, and sedimentation. Weathering breaks rocks into smaller pieces through physical and chemical means. Erosion then transports weathered material, which can sediment in bodies of water. Mass wasting involves downward rock and soil movement due to gravity.
Internal Structure of Earth
This document discusses Earth's interior structure based on seismic wave evidence. It begins by introducing seismic waves like P and S waves. Observing how they travel through Earth reveals its layered structure. The crust and mantle can be detected by changes in wave speeds at boundaries like the Mohorovicic discontinuity. Liquid layers are identified by S waves stopping at the outer core. A solid inner core is known from P wave reflections. Together, precisely tracking seismic wave paths and speeds informs our understanding of Earth's composition and properties within each internal layer.
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The document discusses diastrophism, which refers to deformation of the Earth's crust through natural processes that form geological features. It provides definitions and theories for diastrophism, including isostasy theory, contraction theory, convection current theory, continental drift theory, and expansion theory. The document also discusses stress and strain, defining these terms and describing the three basic types of each. It explains how stress can cause rocks to fold or fault, forming structures like synclines and anticlines.
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- 2. Theory of Plate Tectonics Plate Tectonics Plate Boundaries Causes of Plate Tectonics
- 4. What is Plate Tectonics • The Earth’s crust and upper mantle are broken into sections called plates • Plates move around on top of the mantle like rafts
- 6. What is the Lithosphere? • The crust and part of the upper mantle = lithosphere –100 km thick –Less dense than the material below it so it “floats”
- 7. What is the Asthenoshere? • The plastic layer below the lithosphere = asthenosphere • The plates of the lithosphere float on the asthenosphere
- 9. 2 Types of Plates • Ocean plates - plates below the oceans • Continental plates - plates below the continents
- 10. Questions... • What is the theory of plate tectonics? • What is the lithosphere? • What is the asthenosphere? • What is the connection between the two? • What are the two types of plates?
- 11. Plate Boundaries
- 12. Divergent Boundaries • Boundary between two plates that are moving apart or rifting • RIFTING causes SEAFLOOR SPREADING
- 13. Features of Divergent Boundaries • Mid-ocean ridges • rift valleys • fissure volcanoes
- 17. Convergent Boundaries • Boundaries between two plates that are colliding • There are 3 types…
- 18. Type 1 • Ocean plate colliding with a less dense continental plate • Subduction Zone: where the less dense plate slides under the more dense plate • VOLCANOES occur at subduction zones
- 21. Type 2 • Ocean plate colliding with another ocean plate • The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH
- 24. Type 3 • A continental plate colliding with another continental plate • Have Collision Zones: –a place where folded and thrust faulted mountains form.
- 27. Transform Fault Boundaries • Boundary between two plates that are sliding past each other • EARTHQUAKES along faults
- 29. San Andreas Fault, CA
- 30. Questions... • What are the three types of boundaries? • What direction do plates go for each? • Which boundary has a subduction zone…what occurs at a subduction zone?
- 32. Convection Currents • Hot magma in the Earth moves toward the surface, cools, then sinks again. • Creates convection currents beneath the plates that cause the plates to move.
- 34. Questions... • What causes plates to move? • How is a convection current formed?