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Chapter 7.2Chapter 7.2Restless ContinentsRestless Continents
pgs. 173-176pgs. 173-17610-01-1410-01-14
IN: How did scientists come up IN: How did scientists come up with the idea that the lithosphere with the idea that the lithosphere
is broken into tectonic plates?is broken into tectonic plates?
Restless ContinentsRestless Continents
Wegener’s TheoryWegener’s Theory
Inspired by the puzzle-like fit of the continents Alfred Wegener developed the theory in the early 1900s
Continental Continental driftdrift is the theory that is the theory that continents can drift apart from one another continents can drift apart from one another and have done so in the past.and have done so in the past.
What is Wegener’s Evidence?What is Wegener’s Evidence?
1.) 1.) FossilsFossils of the same plant of the same plant (glossopteris) and animal species (glossopteris) and animal species (mesosaurus) are found on both sides of (mesosaurus) are found on both sides of the Atlantic Ocean.the Atlantic Ocean.
What is Wegener’s Evidence?What is Wegener’s Evidence?
2.) 2.) Geological Evidence: Geological Evidence: Similar types of Similar types of rock and evidence of the same ancient rock and evidence of the same ancient mountain formations were found on mountain formations were found on several continents.several continents.
What is Wegener’s Evidence?
Glacial grooves in rocks on different continents created by receding glaciers that match and are in the same direction.
3.) Evidence of Climate Change:
PangaeaPangaea
Wegener thought that 245 mya all the Wegener thought that 245 mya all the separate continents of today were joined separate continents of today were joined in a in a single landmass the he called single landmass the he called Pangaea Pangaea and a single ocean called and a single ocean called Panthalassa Panthalassa ..
PangaeaPangaea
About 180 mya it began to break into two About 180 mya it began to break into two main pieces. The northern half is known main pieces. The northern half is known as as LaurasiaLaurasia, the southern is known as , the southern is known as GondwanalandGondwanaland..
PangaeaPangaea
About 65 mya, around the time the About 65 mya, around the time the dinosaurs went extinct, they broke into dinosaurs went extinct, they broke into many pieces and looked not too different many pieces and looked not too different from what the continents look like today.from what the continents look like today.
What he didn’t knowWhat he didn’t know
Wegener could not explain what force Wegener could not explain what force could move the continents.could move the continents.
He died in 1930 in an expedition to He died in 1930 in an expedition to Greenland.Greenland.
The Theory of Continental The Theory of Continental Drift Died with Alfred Drift Died with Alfred
Wegener!!!Wegener!!!OUT: Name three pieces of OUT: Name three pieces of evidence Wegener used to evidence Wegener used to explain his theory.explain his theory.
The Theory of Plate TectonicsThe Theory of Plate TectonicsSection 7.2 (Part II)Section 7.2 (Part II)
The Theory of Plate Tectonics states that The Theory of Plate Tectonics states that the lithosphere is divided into tectonic the lithosphere is divided into tectonic plates that move around on the plates that move around on the asthenosphere.asthenosphere.
It was developed in the 1950s and 60s It was developed in the 1950s and 60s and and replacesreplaces Alfred’s theory Alfred’s theory
New EvidenceNew Evidence
New technology from World War II such New technology from World War II such as submarines, the ability to test the age as submarines, the ability to test the age of rocks and sonar helped scientists revive of rocks and sonar helped scientists revive Alfred’s ideas.Alfred’s ideas.
Mid-Ocean RidgeMid-Ocean Ridge
Underwater mountain chains that run Underwater mountain chains that run through Earth’s ocean basins.through Earth’s ocean basins.
Mid-Atlantic RidgeMid-Atlantic Ridge
Ships with sonar began to map the ocean Ships with sonar began to map the ocean floor, and a undersea mountain chain was floor, and a undersea mountain chain was discovered.discovered.
1.)Mid-Ocean Ridges are1.)Mid-Ocean Ridges are
volcanic and are wherevolcanic and are where
sea-floor spreading sea-floor spreading
occurs.occurs.
Sea-floor SpreadingSea-floor Spreading The process by which The process by which newnew oceanic oceanic
lithosphere is created as lithosphere is created as olderolder materials materials are pulled away.are pulled away.
The youngest crust is closest to the MOR, The youngest crust is closest to the MOR, and the oldest is near the continents.and the oldest is near the continents.
RiftsRifts
This also happens on land creating “Rift This also happens on land creating “Rift valleys”valleys”
Magnetic ReversalMagnetic Reversal
2.) Magnetic Reversals, or 2.) Magnetic Reversals, or paleomagnetism, is when Earth’s paleomagnetism, is when Earth’s magnetic poles change place.magnetic poles change place.
This happens 4-5 times every This happens 4-5 times every million yearsmillion years
Tracking Plate MotionTracking Plate Motion
3.) Satellites like GPS track the 3.) Satellites like GPS track the movement of the plates.movement of the plates.
The plates move centimeters per year.The plates move centimeters per year.
OUT: Name three pieces of evidence OUT: Name three pieces of evidence used to describe the Theory of Plate used to describe the Theory of Plate Tectonics.Tectonics.
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