Pgs.44-46 Notes +Images Continental Drift & Paleomagnetism
-Mid-1950s, 2 lines of evidence began to emerge.
-one line came from explorations of the seafloor.
-other line from a new field called peleomagnetism.
Earth's Magnetic Field and Fossil Magnetism
- Curie point- the temp. beyond that at which a ferromagnetic substance exhibits paramagnetism.
-IMPORTANT FACT about rock magnetism: the magnetized minerals don't only show the direction to the poles,but also provide a means of determining the latitude of their origin.
-Rock magnetism provides a record of the direction and distance to the magnetic poles at the time a rock unit was magnetized.
Apparent Polar Wandering
- Discovery- magnetic lignment in iron-rich minerals in lava flows at diff. ages indicating many diff. peleomagnetic poles once existed.
-Polar wandering- magnetic poles migrating through time.
- Wegener's hypothesis: "if the magnetic poles remain st ationary their apparent movement is produced by continental drift.'
- North America and Europe- had similar shapes, just seperated by 30 degrees longitude.
A Scientific Revolution Begins
- Oceanic ridge system-made over the next 2 decades
- New Discoveries: Flat-topped Seamounts:guyots,discovered below sea level.
The Seafloor Spreading Hypothesis
- Oceanic ridges located: above zones of convective upwelling in the mantle
- when rising material from the mantle spreads, the seafloor is carried away to the crest.
- forces fracture the crust+ provide magma to come ad generate new silvers
- seafloor moves away from ridge crest, new crust replaces it.
37-42 NOTES
-Pangeae= single supercontinent.
-Continental drift- lateral movement of continents.
FOSSIL EVIDENCE
- identical fossil organisms were known from rocks in South America+ Africa
- Mesosaurus- an aquatic fish-catching reptile whose fossil remains only in black shales of permian age in Eastern South America+ Southern Africa
- Glossopteris- plant, widely dispersed in Africa, Austrailia, India, and South America.
PANGEAE
- Wegener used fossils, rock types, and ancient climats for evidence to create a jig-saw puzzle of the continents.
- consequence of the breakup of Pangaea= creation of a new ocean basin: the Atlantic
- continents do not break through the ocean floor
- tidal energy is too weak to make continents move.
NOTES PGS. 50-60
-Plate tectonics- the composite of a great variety of ideas that explain the observed motion of Earth's outer shell through the mechanics of subduction and seafloor spreading, which generate Earth's major features(continents, mountains, ocean basins)
-Lithosphere- uppermost mantle
-Plates- broken parts of the lithosphere
-Asthenosphere- weaker region in the mantle
-Tectonic Plates- numerous segments of lithosphere
-Lithospheric plates move 5 cm. per yr.
-Tectonic plates move like coherent units unlike other plates
--Plate Boundaries
1.)Divergent boundaries- two plates move apart
2.)Convergent boundaries- two plates move together
3.)Transform fault boundaries- two plates grind past each other.
-Divergent boundaries- spreading centers
-Rift valley- deep down-faulted structure
-Deep ocean trench- surface expression produced by the descending plate
-Subduction Zones- "convergent boundaries"
-When oceanic lithosphere ages, it cools which causes it to thicken + increase density
-Partial melting- introduction of water leads to melting
-Continental volcanic arcs- mountains which are produced in part by volcanic activity involved with subduction of oceanic lithosphhere
-Volcanic island arc- arc-shaped chain of small volcanic islands
-Most volcanic arcs are in the Western Pacific
- 3rd type of plate boundary- transform fault
-Fracture zones- prominent linear breaks in oceanic crust
Continental Drift & Paleomagnetism
-Mid-1950s, 2 lines of evidence began to emerge.
-one line came from explorations of the seafloor.
-other line from a new field called peleomagnetism.
Earth's Magnetic Field and Fossil Magnetism
- Curie point- the temp. beyond that at which a ferromagnetic substance exhibits paramagnetism.
-IMPORTANT FACT about rock magnetism: the magnetized minerals don't only show the direction to the poles,but also provide a means of determining the latitude of their origin.
-Rock magnetism provides a record of the direction and distance to the magnetic poles at the time a rock unit was magnetized.
Apparent Polar Wandering
- Discovery- magnetic lignment in iron-rich minerals in lava flows at diff. ages indicating many diff. peleomagnetic poles once existed.
-Polar wandering- magnetic poles migrating through time.
- Wegener's hypothesis: "if the magnetic poles remain st ationary their apparent movement is produced by continental drift.'
- North America and Europe- had similar shapes, just seperated by 30 degrees longitude.
A Scientific Revolution Begins
- Oceanic ridge system-made over the next 2 decades
- New Discoveries: Flat-topped Seamounts:guyots,discovered below sea level.
The Seafloor Spreading Hypothesis
- Oceanic ridges located: above zones of convective upwelling in the mantle
- when rising material from the mantle spreads, the seafloor is carried away to the crest.
- forces fracture the crust+ provide magma to come ad generate new silvers
- seafloor moves away from ridge crest, new crust replaces it.
37-42 NOTES
-Pangeae= single supercontinent.
-Continental drift- lateral movement of continents.
FOSSIL EVIDENCE
- identical fossil organisms were known from rocks in South America+ Africa
- Mesosaurus- an aquatic fish-catching reptile whose fossil remains only in black shales of permian age in Eastern South America+ Southern Africa
- Glossopteris- plant, widely dispersed in Africa, Austrailia, India, and South America.
PANGEAE
- Wegener used fossils, rock types, and ancient climats for evidence to create a jig-saw puzzle of the continents.
- consequence of the breakup of Pangaea= creation of a new ocean basin: the Atlantic
- continents do not break through the ocean floor
- tidal energy is too weak to make continents move.
NOTES PGS. 50-60
-Plate tectonics- the composite of a great variety of ideas that explain the observed motion of Earth's outer shell through the mechanics of subduction and seafloor spreading, which generate Earth's major features(continents, mountains, ocean basins)
-Lithosphere- uppermost mantle
-Plates- broken parts of the lithosphere
-Asthenosphere- weaker region in the mantle
-Tectonic Plates- numerous segments of lithosphere
-Lithospheric plates move 5 cm. per yr.
-Tectonic plates move like coherent units unlike other plates
--Plate Boundaries
1.)Divergent boundaries- two plates move apart
2.)Convergent boundaries- two plates move together
3.)Transform fault boundaries- two plates grind past each other.
-Divergent boundaries- spreading centers
-Rift valley- deep down-faulted structure
-Deep ocean trench- surface expression produced by the descending plate
-Subduction Zones- "convergent boundaries"
-When oceanic lithosphere ages, it cools which causes it to thicken + increase density
-Partial melting- introduction of water leads to melting
-Continental volcanic arcs- mountains which are produced in part by volcanic activity involved with subduction of oceanic lithosphhere
-Volcanic island arc- arc-shaped chain of small volcanic islands
-Most volcanic arcs are in the Western Pacific
- 3rd type of plate boundary- transform fault
-Fracture zones- prominent linear breaks in oceanic crust
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