CONTINENTAL DRIFT & SEAFLOOR SPREADING · Part 1: A Controversial Theory •In a 1912 lecture,...
Transcript of CONTINENTAL DRIFT & SEAFLOOR SPREADING · Part 1: A Controversial Theory •In a 1912 lecture,...
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CONTINENTAL DRIFT & SEAFLOOR SPREADING
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Part 1: A Controversial Theory• In a 1912 lecture, German born meteorologist
Alfred Wegener proposed the idea of continental drift.
"Alfred Wegener" by Bildarchiv Preussischer Kulturbesitz, Berlin, Bildid #10005753. Licensed under Public Domain via Wikimedia Commons -https://commons.wikimedia.org/wiki/File:Alfred_Wegener.jpg#/media/File:Alfred_Wegener.jpg
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Part 1: A Controversial Theory• In a 1912 lecture, German born meteorologist
Alfred Wegener proposed the idea of continental drift.
• His idea came from 2 observations• The continents seem to fit together like a
puzzle
• Fossils of animals found on coasts of different continents also aligned "Alfred Wegener" by Bildarchiv Preussischer Kulturbesitz, Berlin, Bildid #10005753. Licensed under Public Domain via Wikimedia Commons -
https://commons.wikimedia.org/wiki/File:Alfred_Wegener.jpg#/media/File:Alfred_Wegener.jpg
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Part 1: A Controversial Theory• In a 1912 lecture, German born meteorologist
Alfred Wegener proposed the idea of continental drift.
• His idea came from 2 observations• The continents seem to fit together like a
puzzle
• Fossils of animals found on coasts of different continents also aligned
• The original land mass he referred to as ‘Pangea,’ meaning ‘all land.’
"Alfred Wegener" by Bildarchiv Preussischer Kulturbesitz, Berlin, Bildid #10005753. Licensed under Public Domain via Wikimedia Commons -https://commons.wikimedia.org/wiki/File:Alfred_Wegener.jpg#/media/File:Alfred_Wegener.jpg
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Continental Drift
"Pangaea continents". Licensed under CC BY-SA 3.0 via Wikimedia Commons -https://commons.wikimedia.org/wiki/File:Pangaea_continents.png#/media/File:Pangaea_continents.png
"Pangea animation 03" by Original upload by en:User:Tbower - http://geomaps.wr.usgs.gov/parks/animate/A08.gif. Licensed under Public Domain via Wikimedia Commons -https://commons.wikimedia.org/wiki/File:Pangea_animation_03.gif#/media/File:Pangea_animation_03.gif
"Snider-Pellegrini Wegener fossil map" by Osvaldocangaspadilla - Own work. Licensed under Public Domain via Wikimedia Commons -https://commons.wikimedia.org/wiki/File:Snider-Pellegrini_Wegener_fossil_map.svg#/media/File:Snider-Pellegrini_Wegener_fossil_map.svg
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Ideas that supported Wegener
• Puzzle pieces: the way the continents fit together
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Ideas that supported Wegener
• Puzzle pieces: the way the continents fit together
• Fossil records: Locations of fossils on continents that would have fit together
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Ideas that supported Wegener
• Puzzle pieces: the way the continents fit together
• Fossil records: Locations of fossils on continents that would have fit together
• Geologic records: nearly identical rock layers on continents that would have fit together
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Ideas that supported Wegener
• Puzzle pieces: the way the continents fit together
• Fossil records: Locations of fossils on continents that would have fit together
• Geologic records: nearly identical rock layers on continents that would have fit together
• Climate change: Plants that live primarily in warmer regions found on multiple continents, including Antarctica. If Pangea were true, the continent would have been in a warmer climateallowing for that plant to survive.
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Wegener gets denied
• Alfred Wegener had a major hole in his theory… He could not explain how, why, or when this occurred.
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Wegener gets denied
• Alfred Wegener had a major hole in his theory… He could not explain how, why, or when this occurred.
• Wegener proposed that the spinning of the Earth somehow caused the continents to move, and they had ‘plowed’ through the oceans.
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Wegener gets denied
• Alfred Wegener had a major hole in his theory… He could not explain how, why, or when this occurred.
• Wegener proposed that the spinning of the Earth somehow caused the continents to move, and they had ‘plowed’ through the oceans.
• This idea was quickly shot down by physicists and geologists.• The Earth spinning cannot cause less dense continental crust to plow
through more dense and rigid oceanic crust.
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Wegener gets denied
• Alfred Wegener had a major hole in his theory… He could not explain how, why, or when this occurred.
• Wegener proposed that the spinning of the Earth somehow caused the continents to move, and they had ‘plowed’ through the oceans.
• This idea was quickly shot down by physicists and geologists.• The Earth spinning cannot cause less dense continental crust to plow
through more dense and rigid oceanic crust.
• Wegener’s idea was rejected by the scientific community and would not be revisited until after his death.
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Part II: Seafloor Spreading• During the 1940s and 1950s, there were huge advances in technology,
specifically in the use of sound waves.
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Part II: Seafloor Spreading• During the 1940s and 1950s, there were huge advances in technology,
specifically in the use of sound waves.
• Scientists began bouncing sound waves off the ocean floor in an effort to make a map of the ocean floor.
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Part II: Seafloor Spreading• During the 1940s and 1950s, there were huge advances in technology,
specifically in the use of sound waves.
• Scientists began bouncing sound waves off the ocean floor in an effort to make a map of the ocean floor.• This led to a major discovery! In the middle of the Atlantic, Pacific, and
other oceans around the world was a chain of mountains and rift valleys.• These are now referred to as ‘mid-ocean ridges.’ We often refer to the one present in
the Atlantic as the mid-Atlantic ridge.
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Part II: Seafloor Spreading• During the 1940s and 1950s, there were huge advances in technology,
specifically in the use of sound waves.
• Scientists began bouncing sound waves off the ocean floor in an effort to make a map of the ocean floor.• This led to a major discovery! In the middle of the Atlantic, Pacific, and
other oceans around the world was a chain of mountains and rift valleys.• These are now referred to as ‘mid-ocean ridges.’ We often refer to the one present in
the Atlantic as the mid-Atlantic ridge.
• Where did these ridges come from?
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Part II: Seafloor Spreading• Bill Nye: Seafloor Spreading Video
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Harry Hess• In the early 1960s, Harry Hess, a Princeton University Professor, proposed his
now famous theory.
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Harry Hess• In the early 1960s, Harry Hess, a Princeton University Professor, proposed his
now famous theory.
• Harry’s theory is called “Seafloor Spreading.”
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Harry Hess• In the early 1960s, Harry Hess, a Princeton University Professor, proposed his
now famous theory.
• Harry’s theory is called “Seafloor Spreading.”
• Hess proposed that less dense, basaltic magma, from beneath the Earth’s crust was pushed upward through the denser ocean floor.
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Harry Hess• In the early 1960s, Harry Hess, a Princeton University Professor, proposed his
now famous theory.
• Harry’s theory is called “Seafloor Spreading.”
• Hess proposed that less dense, basaltic magma, from beneath the Earth’s crust was pushed upward through the denser ocean floor.
• The seafloor then was forced outward from the opening, spreading the seafloor apart.
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Evidence for Spreading• In 1968, the Glomar Challenger began
collecting samples from the ocean floorthat would support Hess’s theory.
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Evidence for Spreading• In 1968, the Glomar Challenger began
collecting samples from the ocean floorthat would support Hess’s theory.
• Scientists collected rocks from the ocean floor, and also drilled samples from different distances between the ridge and the coastline.
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Evidence for Spreading• In 1968, the Glomar Challenger began
collecting samples from the ocean floorthat would support Hess’s theory.
• Scientists collected rocks from the ocean floor, and also drilled samples from different distances between the ridge and the coastline.
• Scientists found that the youngest rocks are found along the mid-ocean ridge, and became increasingly older as you move outward toward the coastline.
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Evidence for Spreading• In 1968, the Glomar Challenger began
collecting samples from the ocean floorthat would support Hess’s theory.
• Scientists collected rocks from the ocean floor, and also drilled samples from different distances between the ridge and the coastline.
• Scientists found that the youngest rocks are found along the mid-ocean ridge, and became increasingly older as you move outward toward the coastline.
• These findings supported both Hess’stheory of seafloor spreading, and Wegener’s theory of continental drift.
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More Supporting Evidence: Magnetic Time Scale
• When rocks containing iron cool, the iron aligns itself with the Earth’s magnetic poles, much like a compass does.
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More Supporting Evidence: Magnetic Time Scale
• When rocks containing iron cool, the iron aligns itself with the Earth’s magnetic poles, much like a compass does.
• Scientists have determined that the Earth’s magnetic poles have reversed multiple times.
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More Supporting Evidence: Magnetic Time Scale
• When rocks containing iron cool, the iron aligns itself with the Earth’s magnetic poles, much like a compass does.
• Scientists have determined that the Earth’s magnetic poles have reversed multiple times.
• Looking at the sea floor iron-containing rocks, they ‘flip’ their polarity as you move away from the mid-ocean ridge.
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More Supporting Evidence: Magnetic Time Scale
• When rocks containing iron cool, the iron aligns itself with the Earth’s magnetic poles, much like a compass does.
• Scientists have determined that the Earth’s magnetic poles have reversed multiple times.
• Looking at the sea floor iron-containing rocks, they ‘flip’ their polarity as you move away from the mid-ocean ridge.
• In other words, the sea floor spreading theory fits perfectly with another theory scientists have had for some time.
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"Oceanic.Stripe.Magnetic.Anomalies.Scheme" by United States Geological Survey -http://pubs.usgs.gov/publications/graphics/Fig7.gif. Licensed under Public Domain via Wikimedia Commons -https://commons.wikimedia.org/wiki/File:Oceanic.Stripe.Magnetic.Anomalies.Scheme.gif#/media/File:Oceanic.Stripe.Magnetic.Anomalies.Scheme.gif
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"Oceanic.Stripe.Magnetic.Anomalies.Scheme" by United States Geological Survey -http://pubs.usgs.gov/publications/graphics/Fig7.gif. Licensed under Public Domain via Wikimedia Commons -https://commons.wikimedia.org/wiki/File:Oceanic.Stripe.Magnetic.Anomalies.Scheme.gif#/media/File:Oceanic.Stripe.Magnetic.Anomalies.Scheme.gif
• Seafloor Spreading Song