Sea-Floor Spreading Notes - Jenny
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Scientists in the 1950s used sonar to map the mid-ocean ridge and discovered it was not flat but made of underwater mountains. This discovery led them to research what the ridge was and how it formed. Evidence from molten rock formations, magnetic patterns in the ocean crust, and sediment core samples supported Harry Hess's theory from 1960 that the ocean floors spread from the mid-ocean ridge in a conveyor belt-like motion, pushing the continents. This process of sea-floor spreading continually recycles the ocean crust through subduction at deep ocean trenches.
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Sea floor spreading
The document summarizes evidence that supports the theory of seafloor spreading and plate tectonics. It describes how Harry Hess first proposed in 1962 that new ocean crust is formed at mid-ocean ridges through volcanic activity and magma cooling. As more magma is added, it pushes older ocean crust further from the ridges, providing evidence that the plates are moving. Studies of magnetic reversals in ocean floor basalts also indicate the age of the crust increases further from ridges, confirming seafloor is continually being created and destroyed over time.
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1st quarter grade 10 science - seafloor spreading theory and its evidences good for 2 hours.I hope the videos included will play
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This ppt is about 3 theories of plate tectonics: Continental drift, seafloor spreading and theory of plate tectonics
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Three key points about hotspots:
1) Hotspots are volcanic regions thought to be fed by anomalously hot mantle material rising independently of tectonic plate boundaries. Well-known examples include Hawaii, Iceland, and Yellowstone.
2) There are two hypotheses for the origin of hotspots - one involving mantle plumes rising from the core-mantle boundary, the other involving passive rising of melt from shallow depths.
3) Hotspot tracks provide evidence for the plate tectonics model, as volcanic chains like the Hawaiian Islands can be explained by plates migrating over fixed mantle plumes.
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.
Plate tectonics
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Plate tectonics
The document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed the idea of continental drift in 1915, noting that continents seem to fit together. Over decades, further evidence was collected from matching fossil records, mountain ranges, and coastline shapes between separated continents. In the 1960s, the theory of plate tectonics emerged to explain these observations, proposing that the Earth's lithosphere is broken into plates that move over Earth's asthenosphere. There are three types of plate boundaries - divergent where new crust forms, convergent where plates collide, and transform where plates slide past each other.
Sea floor spreading powerpoint
The document discusses sea floor spreading and the evidence that supports this theory. It describes how molten material rises up from the mantle at mid-ocean ridges, cools and forms new crust that constantly pushes older crust outward. It spreads until the dense oceanic crust sinks back into the mantle at deep ocean trenches in the process of subduction, which balances out the growth at ridges. Key evidence includes magnetic stripes in the crust, drilling samples, and the overall structure of ridges and trenches.
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Sea floor spreading
The document summarizes evidence that supports the theory of seafloor spreading and plate tectonics. It describes how Harry Hess first proposed in 1962 that new ocean crust is formed at mid-ocean ridges through volcanic activity and magma cooling. As more magma is added, it pushes older ocean crust further from the ridges, providing evidence that the plates are moving. Studies of magnetic reversals in ocean floor basalts also indicate the age of the crust increases further from ridges, confirming seafloor is continually being created and destroyed over time.
seafloor spreading theory
1st quarter grade 10 science - seafloor spreading theory and its evidences good for 2 hours.I hope the videos included will play
Plate Tectonics
This ppt is about 3 theories of plate tectonics: Continental drift, seafloor spreading and theory of plate tectonics
Hotspots
Three key points about hotspots:
1) Hotspots are volcanic regions thought to be fed by anomalously hot mantle material rising independently of tectonic plate boundaries. Well-known examples include Hawaii, Iceland, and Yellowstone.
2) There are two hypotheses for the origin of hotspots - one involving mantle plumes rising from the core-mantle boundary, the other involving passive rising of melt from shallow depths.
3) Hotspot tracks provide evidence for the plate tectonics model, as volcanic chains like the Hawaiian Islands can be explained by plates migrating over fixed mantle plumes.
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.
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The document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed the idea of continental drift in 1915, noting that continents seem to fit together. Over decades, further evidence was collected from matching fossil records, mountain ranges, and coastline shapes between separated continents. In the 1960s, the theory of plate tectonics emerged to explain these observations, proposing that the Earth's lithosphere is broken into plates that move over Earth's asthenosphere. There are three types of plate boundaries - divergent where new crust forms, convergent where plates collide, and transform where plates slide past each other.
Sea floor spreading powerpoint
The document discusses sea floor spreading and the evidence that supports this theory. It describes how molten material rises up from the mantle at mid-ocean ridges, cools and forms new crust that constantly pushes older crust outward. It spreads until the dense oceanic crust sinks back into the mantle at deep ocean trenches in the process of subduction, which balances out the growth at ridges. Key evidence includes magnetic stripes in the crust, drilling samples, and the overall structure of ridges and trenches.
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.
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.
Transform Plate Boundaries
This document discusses tectonic plates and transform plate boundaries. It notes that tectonic plates are large pieces of rock that make up Earth's crust, and there are two main types - oceanic and continental plates. At transform boundaries, the plates move horizontally past one another, driven by convection currents in the underlying mantle. When the plates rub together at these boundaries, it causes huge stress that results in earthquakes, faults, and tsunamis.
Transform boundary
A transform boundary is a plate boundary where plates move horizontally past each other in opposite directions. Convection currents in the mantle cause plate movement. Transform boundaries collect energy from plate movement that is eventually released through earthquakes and tsunamis, as seen at the San Andreas Fault and from a Pacific Ocean earthquake that caused a major tsunami. While they do not form volcanoes or mountains, transform boundaries can create dangerous earthquakes and tsunamis.
Sea Floor spreading
The document discusses the theory of seafloor spreading, where new ocean crust is formed at mid-ocean ridges as tectonic plates move apart, and magnetic patterns in rocks on the ocean floor provide evidence of periodic reversals of the Earth's magnetic field. Analysis of magnetic stripes on both sides of ocean ridges that appear to be mirror images supports the idea that the seafloor is actively spreading.
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The document discusses evidence that supports the theory of continental drift and the existence in the past of the supercontinent Pangaea. It provides examples of matching geological formations and fossil records found across continents now separated by oceans, including similar coal deposits in Antarctica, North America and the UK from the Carboniferous period; glacial striations matching between Brazil and West Africa; and the reptile Mesosaurus fossilized in sediments in South America and South Africa dated to around 280 million years ago. It also describes how Jack Oliver's 1968 research paper provided further evidence that finally convinced the scientific community to accept continental drift.
Sea floor spreading
1) The Mid-Ocean Ridge system circles the Earth along the ocean floor and is over 56,000 km long. It forms at divergent plate boundaries where new oceanic crust is continually being formed.
2) Scientists use sonar to map the ocean floor and study its features like the Mid-Ocean Ridge. Sonar bounces sound waves off underwater objects to image the seafloor.
3) Evidence like magnetic stripes in ocean crust and samples dug from the seafloor support the theory of sea floor spreading, where new crust forms at ridges and spreads out over time.
WHAT IS A PLATE? MAJOR PLATES. Types of Earth’s Crust. Plate Boundary
The document discusses plate tectonics and the key concepts of plate tectonic theory. It describes how the lithosphere is broken into large plates that move over Earth's surface, driven by convection currents in the underlying mantle. It outlines the three main types of plate boundaries - divergent boundaries where new crust forms, transform boundaries where plates slide past each other, and convergent boundaries where plates collide and one slides under the other. It also discusses the evidence that supported the development of plate tectonic theory, such as seafloor spreading and magnetic reversals recorded in oceanic crust.
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The document discusses heat transfer through conduction, convection, and radiation. It explains that convection occurs when heat transfer causes fluid movement within a substance. In Earth's mantle, large convection currents are driven by heat from the core, causing the mantle to circulate. This circulation of the mantle drives the movement of tectonic plates at Earth's surface.
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.
Processes and landforms along plate boundaries
This document defines and provides examples of different types of landforms formed by various geological processes. It discusses aeolian forms like dunes, loess, and mushroom rocks shaped by wind; erosional landforms such as mesas, buttes, and canyons formed by erosion; mountainous landforms including volcanoes, hills, and valleys; glacial landforms resulting from glacier activity; fluvial landforms near rivers like deltas, meanders and coastal landforms such as sea cliffs, peninsulas and plains.
The seafloor spreading
Scientists used new techniques like sonar and submersibles in the 1950s-1960s to better observe the ocean floor. They discovered mid-ocean ridges and the theory of seafloor spreading, where new crust forms at ridges and pushes plates apart over time. The movement of plates causes the splitting of continents and creation of oceans. Magnetic patterns in ocean crust provided evidence that seafloor spreading occurs and plates have moved over millions of years.
Sea floor spreading
1) Tubeworms survive through a symbiotic relationship with bacteria that live inside them. The bacteria convert chemicals from deep sea vents into food for the worm.
2) Sonar uses sound waves to determine the distance to underwater objects by measuring the echo return time.
3) Sea-floor spreading was discovered by Harry Hess in the 1960s and explains how new ocean crust continually forms at mid-ocean ridges, pushing older rocks away.
TYPES OF PLATE BOUNDARIES
This document discusses three main types of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaries. It provides examples and describes the geological effects of each boundary type. It also discusses processes at divergent boundaries like mid-ocean ridges and continental rift valleys. Convergent boundaries include oceanic-oceanic convergence forming island arcs, and continental-oceanic convergence forming volcanic mountain ranges. Transform boundaries involve strike-slip faulting along plate edges. Additionally, the document touches on hot spot volcanism unrelated to plate boundaries.
Continental drift theory discuss
Continental Drift Theory proposed that the continents were once joined together in a single landmass called Pangaea. Evidence for this theory included:
1) The matching coastline edges of continents like Africa and South America, and geological features that lined up across continents.
2) Similar fossil species found in matching geological formations along coastlines now separated by oceans.
3) Identical aged rock formations and tillite deposits along the separated coastlines, indicating they were once attached.
This theory was initially rejected due to the lack of an explained physical mechanism for continental drift, but was later supported by the development of plate tectonic theory.
Continental drift &and sea floor spreading
The document discusses the theories of continental drift, seafloor spreading, and plate tectonics. It provides details on the original proponent of continental drift theory, Alfred Wegener, in 1915. It also outlines various geological, climatic, and biological evidence that supports continental drift. The document then discusses the sea floor spreading theory proposed by Harry Hess in the 1960s, which helped explain continental drift. It notes evidence that the ocean floor becomes progressively younger near mid-ocean ridges. Finally, it describes how the theories of continental drift and sea floor spreading were combined into the comprehensive theory of plate tectonics.
Continental drift theory
Alfred Wegener first proposed the theory of continental drift in 1910, suggesting that the continents were once joined together in a supercontinent called Pangaea. Wegener provided three lines of evidence to support his theory: the matching shapes of continental coastlines, matching fossil distributions across continents, and evidence that past climates did not match current continental positions. While his theory was initially rejected due to the lack of a mechanism, it was later supported by the discovery of seafloor spreading in the 1960s, which provided a process to explain how and why continents move over Earth's surface.
Continental Drift
1) Alfred Wegener proposed the theory of continental drift, which suggested that the continents were once joined together in a supercontinent called Pangaea before drifting apart over millions of years.
2) To support his theory, Wegener presented four pieces of evidence: the matching shapes of continental edges, identical fossil distributions, matching rock formations, and evidence of past climate zones that no longer align with the continents' current locations.
3) Despite this evidence, Wegener's contemporaries rejected his theory because he could not explain the mechanism that caused the continents to move. Acceptance of the theory required understanding how and why continental drift occurred.
Continental drift theory
The Continental Drift theory proposed by Alfred Wegener in 1912 suggested that the continents were once joined together in a single landmass called Pangaea. Wegener did not have proof of his theory at the time, but later evidence from matching fossil distributions, identical rock formations between continents, and the same mountain ranges provided support. This included fossils of Glossopteris found across regions of the former supercontinent Gondwanaland. Although controversial when first introduced, the development of the theory of plate tectonics provided the mechanism of plate movement driven by convection currents to explain how the continents could drift apart.
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.
SEA-FLOOR-SPREADING SEA-FLOOR-SPREADINGpptx
The document summarizes evidence for sea-floor spreading at mid-ocean ridges. Scientists used sonar to map the mid-ocean ridge and discovered the ocean floor was not flat, peaking their curiosity. Studies of rocks showed evidence of molten material erupting at ridges. Magnetic stripe patterns on both sides of ridges, matching Earth's magnetic field reversals, supported the idea that new seafloor spreads outward from ridges. Drilling samples found younger rocks near ridges, older farther away. Subduction pulls older, denser seafloor into trenches, allowing continuous renewal of seafloor at ridges.
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.
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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.
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.
Transform Plate Boundaries
This document discusses tectonic plates and transform plate boundaries. It notes that tectonic plates are large pieces of rock that make up Earth's crust, and there are two main types - oceanic and continental plates. At transform boundaries, the plates move horizontally past one another, driven by convection currents in the underlying mantle. When the plates rub together at these boundaries, it causes huge stress that results in earthquakes, faults, and tsunamis.
Transform boundary
A transform boundary is a plate boundary where plates move horizontally past each other in opposite directions. Convection currents in the mantle cause plate movement. Transform boundaries collect energy from plate movement that is eventually released through earthquakes and tsunamis, as seen at the San Andreas Fault and from a Pacific Ocean earthquake that caused a major tsunami. While they do not form volcanoes or mountains, transform boundaries can create dangerous earthquakes and tsunamis.
Sea Floor spreading
The document discusses the theory of seafloor spreading, where new ocean crust is formed at mid-ocean ridges as tectonic plates move apart, and magnetic patterns in rocks on the ocean floor provide evidence of periodic reversals of the Earth's magnetic field. Analysis of magnetic stripes on both sides of ocean ridges that appear to be mirror images supports the idea that the seafloor is actively spreading.
Continental Drift Theory-Abhinav gupta
The document discusses evidence that supports the theory of continental drift and the existence in the past of the supercontinent Pangaea. It provides examples of matching geological formations and fossil records found across continents now separated by oceans, including similar coal deposits in Antarctica, North America and the UK from the Carboniferous period; glacial striations matching between Brazil and West Africa; and the reptile Mesosaurus fossilized in sediments in South America and South Africa dated to around 280 million years ago. It also describes how Jack Oliver's 1968 research paper provided further evidence that finally convinced the scientific community to accept continental drift.
Sea floor spreading
1) The Mid-Ocean Ridge system circles the Earth along the ocean floor and is over 56,000 km long. It forms at divergent plate boundaries where new oceanic crust is continually being formed.
2) Scientists use sonar to map the ocean floor and study its features like the Mid-Ocean Ridge. Sonar bounces sound waves off underwater objects to image the seafloor.
3) Evidence like magnetic stripes in ocean crust and samples dug from the seafloor support the theory of sea floor spreading, where new crust forms at ridges and spreads out over time.
WHAT IS A PLATE? MAJOR PLATES. Types of Earth’s Crust. Plate Boundary
The document discusses plate tectonics and the key concepts of plate tectonic theory. It describes how the lithosphere is broken into large plates that move over Earth's surface, driven by convection currents in the underlying mantle. It outlines the three main types of plate boundaries - divergent boundaries where new crust forms, transform boundaries where plates slide past each other, and convergent boundaries where plates collide and one slides under the other. It also discusses the evidence that supported the development of plate tectonic theory, such as seafloor spreading and magnetic reversals recorded in oceanic crust.
CONVECTION-AND-THE-MANTLE.ppt
The document discusses heat transfer through conduction, convection, and radiation. It explains that convection occurs when heat transfer causes fluid movement within a substance. In Earth's mantle, large convection currents are driven by heat from the core, causing the mantle to circulate. This circulation of the mantle drives the movement of tectonic plates at Earth's surface.
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.
Processes and landforms along plate boundaries
This document defines and provides examples of different types of landforms formed by various geological processes. It discusses aeolian forms like dunes, loess, and mushroom rocks shaped by wind; erosional landforms such as mesas, buttes, and canyons formed by erosion; mountainous landforms including volcanoes, hills, and valleys; glacial landforms resulting from glacier activity; fluvial landforms near rivers like deltas, meanders and coastal landforms such as sea cliffs, peninsulas and plains.
The seafloor spreading
Scientists used new techniques like sonar and submersibles in the 1950s-1960s to better observe the ocean floor. They discovered mid-ocean ridges and the theory of seafloor spreading, where new crust forms at ridges and pushes plates apart over time. The movement of plates causes the splitting of continents and creation of oceans. Magnetic patterns in ocean crust provided evidence that seafloor spreading occurs and plates have moved over millions of years.
Sea floor spreading
1) Tubeworms survive through a symbiotic relationship with bacteria that live inside them. The bacteria convert chemicals from deep sea vents into food for the worm.
2) Sonar uses sound waves to determine the distance to underwater objects by measuring the echo return time.
3) Sea-floor spreading was discovered by Harry Hess in the 1960s and explains how new ocean crust continually forms at mid-ocean ridges, pushing older rocks away.
TYPES OF PLATE BOUNDARIES
This document discusses three main types of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaries. It provides examples and describes the geological effects of each boundary type. It also discusses processes at divergent boundaries like mid-ocean ridges and continental rift valleys. Convergent boundaries include oceanic-oceanic convergence forming island arcs, and continental-oceanic convergence forming volcanic mountain ranges. Transform boundaries involve strike-slip faulting along plate edges. Additionally, the document touches on hot spot volcanism unrelated to plate boundaries.
Continental drift theory discuss
Continental Drift Theory proposed that the continents were once joined together in a single landmass called Pangaea. Evidence for this theory included:
1) The matching coastline edges of continents like Africa and South America, and geological features that lined up across continents.
2) Similar fossil species found in matching geological formations along coastlines now separated by oceans.
3) Identical aged rock formations and tillite deposits along the separated coastlines, indicating they were once attached.
This theory was initially rejected due to the lack of an explained physical mechanism for continental drift, but was later supported by the development of plate tectonic theory.
Continental drift &and sea floor spreading
The document discusses the theories of continental drift, seafloor spreading, and plate tectonics. It provides details on the original proponent of continental drift theory, Alfred Wegener, in 1915. It also outlines various geological, climatic, and biological evidence that supports continental drift. The document then discusses the sea floor spreading theory proposed by Harry Hess in the 1960s, which helped explain continental drift. It notes evidence that the ocean floor becomes progressively younger near mid-ocean ridges. Finally, it describes how the theories of continental drift and sea floor spreading were combined into the comprehensive theory of plate tectonics.
Continental drift theory
Alfred Wegener first proposed the theory of continental drift in 1910, suggesting that the continents were once joined together in a supercontinent called Pangaea. Wegener provided three lines of evidence to support his theory: the matching shapes of continental coastlines, matching fossil distributions across continents, and evidence that past climates did not match current continental positions. While his theory was initially rejected due to the lack of a mechanism, it was later supported by the discovery of seafloor spreading in the 1960s, which provided a process to explain how and why continents move over Earth's surface.
Continental Drift
1) Alfred Wegener proposed the theory of continental drift, which suggested that the continents were once joined together in a supercontinent called Pangaea before drifting apart over millions of years.
2) To support his theory, Wegener presented four pieces of evidence: the matching shapes of continental edges, identical fossil distributions, matching rock formations, and evidence of past climate zones that no longer align with the continents' current locations.
3) Despite this evidence, Wegener's contemporaries rejected his theory because he could not explain the mechanism that caused the continents to move. Acceptance of the theory required understanding how and why continental drift occurred.
Continental drift theory
The Continental Drift theory proposed by Alfred Wegener in 1912 suggested that the continents were once joined together in a single landmass called Pangaea. Wegener did not have proof of his theory at the time, but later evidence from matching fossil distributions, identical rock formations between continents, and the same mountain ranges provided support. This included fossils of Glossopteris found across regions of the former supercontinent Gondwanaland. Although controversial when first introduced, the development of the theory of plate tectonics provided the mechanism of plate movement driven by convection currents to explain how the continents could drift apart.
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.
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The document summarizes evidence for sea-floor spreading at mid-ocean ridges. Scientists used sonar to map the mid-ocean ridge and discovered the ocean floor was not flat, peaking their curiosity. Studies of rocks showed evidence of molten material erupting at ridges. Magnetic stripe patterns on both sides of ridges, matching Earth's magnetic field reversals, supported the idea that new seafloor spreads outward from ridges. Drilling samples found younger rocks near ridges, older farther away. Subduction pulls older, denser seafloor into trenches, allowing continuous renewal of seafloor at ridges.
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.
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This document discusses evidence that supports continental drift and plate tectonics theories. It describes how the Earth's crust is divided into plates that move over time, occasionally colliding or splitting apart. Fossil, rock formation, and climate data from separated continents provided early evidence that landmasses have drifted over hundreds of millions of years. Studies of the ocean floor revealed patterns of magnetic polarity reversals and symmetrical magnetic strips that supported the hypothesis of sea floor spreading at mid-ocean ridges, with new crust forming and pushing older crust farther outward over time. Together this evidence established plate tectonics as the mechanism explaining continental movement and geological phenomena like earthquakes and volcanoes.
Sea Floor Spreading Theory.ppt
Sea floor spreading occurs as new oceanic crust is formed at mid-ocean ridges. In the 1960s, scientists found evidence for sea floor spreading from volcanic rocks on the sea floor, magnetic patterns in the rocks, and by dating rocks that were older further from the ridges. Oceanic crust is also destroyed as it subducts under continental crust at deep ocean trenches.
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Scientists in the 1960s found three key pieces of evidence that supported the theory of sea floor spreading:
1) Rock samples from mid-ocean ridges showed pillow lava formations, indicating recent volcanic eruptions of molten material.
2) Magnetic readings of ocean crust revealed a pattern of magnetic stripes matching the periodic reversal of Earth's magnetic poles over time.
3) Drilling samples found that rocks near mid-ocean ridges were younger than those further away, supporting the idea that new crust was generated at ridges.
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Scientists in the 1960s found three key pieces of evidence that supported the theory of sea floor spreading:
1) Rock samples from mid-ocean ridges showed pillow lava formations, indicating recent volcanic eruptions of molten material.
2) Magnetic readings of ocean crust revealed a pattern of magnetic stripes matching the periodic reversal of Earth's magnetic poles over time.
3) Drilling samples found that rocks near mid-ocean ridges were younger than those further away, supporting the idea that new crust was generated at ridges.
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Scientists in the 1960s found three key pieces of evidence that supported the theory of sea floor spreading:
1) Rock samples from mid-ocean ridges showed pillow lava formations, indicating recent volcanic eruptions of molten material.
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This document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed continental drift in 1912 and how the theory was rejected until the 1950s. The discovery of mid-ocean ridges provided evidence that the ocean floors were spreading and pushing the continents apart. Rocks and fossils found on separated continents matched and indicated they were once joined together in a supercontinent called Pangaea. The theory of plate tectonics emerged, linking continental drift and seafloor spreading to explain how the Earth's crust has evolved over time through the movement of tectonic plates.
Chapter 3 Plate Tectonics
This document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed continental drift in 1912 and how the theory was rejected until the 1950s. The discovery of mid-ocean ridges provided evidence that the ocean floors were spreading and pushing the continents apart. Rocks and fossils found on separated continents matched and indicated they were once joined as the supercontinent Pangaea. Plate tectonics emerged as a unified theory to explain these observations.
Chapter 3 Plate Tectonics
This document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed continental drift in 1912 and how the theory was rejected until the 1950s. The discovery of mid-ocean ridges provided evidence that the ocean floors were spreading and pushing the continents apart. Rock and fossil evidence also indicated that continents were once joined together in a supercontinent called Pangaea. The theory of plate tectonics emerged, linking ideas of continental drift and seafloor spreading to explain how tectonic plates move and cause geological features across the Earth.
Continental Drift - Plate tectonic - Theory evidences.pptx
Alfred Wegener first proposed the theory of continental drift in 1915, suggesting that the continents were once joined together and have since drifted apart. He provided evidence from matching landforms, fossil distributions, and past climate patterns. However, his theory was rejected by many geologists at the time due to lack of explanation for the driving forces. It was not until the 1950s and discoveries of sea floor spreading and plate tectonics that Wegener's theory became widely accepted.
Dynamic Earth Chapter 3 Plate Tectonics 1
This document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed continental drift in 1912, but it was not widely accepted until the 1950s with the discovery of mid-ocean ridges and evidence of seafloor spreading. The theory of plate tectonics links continental drift and seafloor spreading and explains how the Earth's crust has evolved over time as the lithospheric plates have moved and collided.
Plate Tectonics I
This document provides an overview of plate tectonics and the key individuals and discoveries that led to the development of the theory. It discusses Alfred Wegener's idea of continental drift in the early 20th century, which was initially rejected. It then covers the discoveries of the mid-ocean ridge system and magnetic striping of the ocean floor in the 1950s-60s, which provided evidence that the continents are moving and new crust is generated at ocean ridges through seafloor spreading. This led to the acceptance of plate tectonics as a scientific theory to explain geological phenomena.
Plate Tectonics - Chapter 5
Geologists have learned about Earth's interior through examining rock samples and studying seismic waves. Temperature and pressure both increase with depth inside Earth. The crust and mantle are divided into layers with different physical properties. Convection currents in the mantle are driven by heat from the core and cause the tectonic plates to slowly move over time. The theory of plate tectonics explains how new crust forms at mid-ocean ridges and old crust is recycled into the mantle at subduction zones, causing the plates to drift apart or collide together over hundreds of millions of years.
Sea floor spreading2
Sea-floor spreading is the process that continually adds new material to the ocean floor. Molten material rises up from the mantle at mid-ocean ridges and erupts, pushing the oceanic plates apart as it cools and forms new crust. Evidence for sea-floor spreading includes pillow basalts and magnetic stripe patterns in the ocean crust that record reversals in Earth's magnetic field. Drilling samples also show that rocks get progressively older farther from mid-ocean ridges. Subduction is the process where oceanic plates plunge back into the mantle at deep-sea trenches, allowing the ocean floor to continuously renew itself over hundreds of millions of years.
Sci 10 - Lesson 4.pdf
The document summarizes evidence that supports plate tectonic theory and continental drift. It describes how the continents fit together like puzzle pieces, examples of matching rock formations and fossil distributions between continents, and patterns in magnetic stripes on ocean floors that support the ideas of seafloor spreading and plate movement over time. New ocean crust is formed at mid-ocean ridges through convection currents in the mantle, which also act to push and pull plates along tectonic boundaries.
Prema
plate tectonic theory,how seafloor spread and how mountain are build,polar wandering, Hot spot, kober's geosynclinal orogen hypothesis
Earth's interior bs 1st year
This document summarizes the internal structure of Earth based on seismic wave studies. It describes the crust, mantle, outer core, and inner core. The crust is thinner under oceans than continents and consists of less dense granite and more dense basalt. There is a sharp boundary between the crust and mantle. The mantle is divided into upper and lower sections. The outer core is liquid while the inner core is solid. Plate tectonics involves rigid lithospheric plates floating on the mantle that move and interact at boundaries.
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Continental Drift - Plate tectonic - Theory evidences.pptx
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Sea-Floor Spreading Notes - Jenny
- 2. Mapping the Mid-Ocean Ridge • The mid-ocean ridge is the longest chain of mountains in the world. • In the 1950s scientist mapped the mid-ocean ridge using sonar. •Sonar is an instrument that uses sound waves to measure distance. • It bounces sound waves off underwater objects and records the echoes of these sounds.
- 3. •The time that it takes the echo indicates the distance to the object. • The scientists found out that the ocean floor was not flat. •This discovery peaked their curiosity to discover what the ridge was and how it got there.
- 4. There are huge mountain ranges called ridges. Ex: Mid-Atlantic Ridge
- 5. The Global Mid-Oceanic Ridge System
- 7. Evidence for Sea-Floor Spreading • In 1960, Harry Hess studied Wegener’s theory. • Hess proposed the radical idea that the ocean floors move like a conveyer belt, which in turn move the continents.
- 8. Evidence for Sea-Floor Spreading •This movement begins at the mid-ocean ridge, which forms along in a crack in the oceanic crust. • At the mid-ocean ridge, molten materials rise from the mantle and erupts. •The molten material spreads out, pushing older rock to both sides of the ridge.
- 9. • Hess called this process Sea-Floor Spreading. • Molten material, magnetic stripes, and drilling samples supported Hess’s theory.
- 10. Evidence from Molten Material • In the 1960s, scientist used a small submarine called Alvin to explore the ocean floor. • Alvin’s crew found rocks shaped like pillows or toothpaste squeezed from a tube. • These rocks showed that molten material had erupted many different times from cracks along the mid-ocean ridge.
- 11. Evidence from Magnetic Stripes • The Earth is like a giant magnet with a north and south pole. • The Earth’s magnetic poles reversed themselves 780,000 years ago. •Rocks on the ocean floor are in a pattern of magnetized stripes. •These stripes show when the Earth reversed its magnetic field.
- 13. Reversals happen on average only about once every 250,000 years, and they take hundreds if not thousands of years to complete. The magnetic field does not vanish during this time.
- 14. More Evidence from Magnetic Stripes • Molten material contains iron. •As it cooled, the iron bits lined up in the direction of Earth’s magnetic poles. •When the rock hardened, the iron was locked in place, giving the rocks a permanent “magnetic memory”.
- 15. More Evidence from Magnetic Stripes •Scientist recorded this “magnetic memory” on both sides of the mid- ocean ridge. • They found a stripe of when the magnetic field pointed north and a parallel stripe that pointed south. •Rock that hardens at the same time would have the same magnetic memory.
- 16. Evidence from Drilling Samples The Glomar Challenger is a drilling ship that recovered drilling samples from the ocean floor. • They studied the age of the rocks sampled. • They found that the farther from the ridge, the older the rock. • The youngest rocks were at the center of the ridge.
- 17. Subduction at Deep-Ocean Trenches • The ocean floor plunges into deep underwater canyons called deep-ocean trenches. • Subduction takes place where there are deep-ocean trenches. • New oceanic crust is hot. • It moves away from the mid-ocean ridge and cools, making it more dense.
- 18. • Gravity pulls the denser, older crust down beneath the trench. • Subduction allows the ocean floor to sink back into the mantle that takes tens of millions of years to recycle.
- 19. Subduction and Earth’s Ocean’s •Subduction and sea-floor spreading change the size and shape of the oceans. • The ocean floor is renewed every 200 million years.
- 20. Subduction in the Pacific Ocean • The Pacific Ocean covers 1/3 of the planet, but it is shrinking. • There is a ring of trenches that surrounds the Pacific Ocean. • This occurs because a deep ocean trench swallows more oceanic crust than the mid- ocean ridge can produce. • If new crust is not added fast enough, the width of the ocean shrinks.
- 22. Subduction in the Atlantic Ocean • The Atlantic Ocean is expanding. • The Atlantic Ocean has only a few trenches. • The Atlantic Ocean floor is attached to the continental crust of the continents. • As the sea-floor spreads, the continents along that edge also move.