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Questions and Answers
What does paleomagnetism primarily focus on?
What does paleomagnetism primarily focus on?
- The examination of ancient magnetic fields (correct)
- The study of fossilized remains
- The exploration of coal deposits
- The analysis of geological formations
What indicates that Earth's magnetic poles have reversed over geological time?
What indicates that Earth's magnetic poles have reversed over geological time?
- Presence of large coal deposits
- Significant warming of the planet
- Different magnetizations in rocks from various locations (correct)
- Alignment of tectonic plates
Which type of plate boundary is characterized by plates pushing together?
Which type of plate boundary is characterized by plates pushing together?
- Transform
- Subductive
- Convergent (correct)
- Divergent
Which of the following plates is classified as a primary plate?
Which of the following plates is classified as a primary plate?
What geophysical evidence supports the understanding of the Earth's internal structure?
What geophysical evidence supports the understanding of the Earth's internal structure?
What evidence did Alfred Wegener use to indicate past climatic conditions?
What evidence did Alfred Wegener use to indicate past climatic conditions?
Which fossil evidence suggests that continents were once connected during the Triassic Period?
Which fossil evidence suggests that continents were once connected during the Triassic Period?
What did the glacial till deposits in the southern hemisphere indicate about continental formation?
What did the glacial till deposits in the southern hemisphere indicate about continental formation?
What discovery in the 1950s significantly contributed to the acceptance of Wegener's theories?
What discovery in the 1950s significantly contributed to the acceptance of Wegener's theories?
What plant fossil was used to support the idea of continental drift during the Pennsylvanian Period?
What plant fossil was used to support the idea of continental drift during the Pennsylvanian Period?
Which of the following does NOT support the theory of continental drift?
Which of the following does NOT support the theory of continental drift?
What type of evidence suggests that ice moved inland from oceans in historical landmasses?
What type of evidence suggests that ice moved inland from oceans in historical landmasses?
What does paleoclimatology primarily study?
What does paleoclimatology primarily study?
What composition leads to the lower density of continental plates compared to oceanic plates?
What composition leads to the lower density of continental plates compared to oceanic plates?
What is the primary mechanism driving plate movement according to the Mantle Convection Theory?
What is the primary mechanism driving plate movement according to the Mantle Convection Theory?
Which statement accurately describes oceanic crust compared to continental crust?
Which statement accurately describes oceanic crust compared to continental crust?
What does the Plate Tectonics Theory help explain regarding Earth's geological features?
What does the Plate Tectonics Theory help explain regarding Earth's geological features?
According to the Slab Pull Theory, what drives the movement of tectonic plates?
According to the Slab Pull Theory, what drives the movement of tectonic plates?
How fast can lithospheric plates move according to geological data?
How fast can lithospheric plates move according to geological data?
Which concept suggests that continental drift is driven by energy from the Earth's interior?
Which concept suggests that continental drift is driven by energy from the Earth's interior?
What concept explains why continents seem to fit together like puzzle pieces?
What concept explains why continents seem to fit together like puzzle pieces?
What are the two main types of lithospheric plates discussed?
What are the two main types of lithospheric plates discussed?
What is the main idea behind isostasy?
What is the main idea behind isostasy?
Which scientist is associated with proposing the Continental Drift Theory?
Which scientist is associated with proposing the Continental Drift Theory?
What was the supercontinent called that existed around 250 million years ago?
What was the supercontinent called that existed around 250 million years ago?
What did the Raisin Theory suggest about the Earth's structure over time?
What did the Raisin Theory suggest about the Earth's structure over time?
Which two supercontinents did Pangaea begin to split into during the Triassic period?
Which two supercontinents did Pangaea begin to split into during the Triassic period?
How do the densities of continental and oceanic crusts compare?
How do the densities of continental and oceanic crusts compare?
What major geological process continues to influence the movement of continents today?
What major geological process continues to influence the movement of continents today?
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Study Notes
Introduction to Plate Tectonics
- Continents fit together like puzzle pieces, suggesting a scientific explanation: Plate Tectonics.
- At the start of the 20th century, the Raisin Theory likened Earth to a shrinking raisin, causing the crust to contract and form mountains and ocean basins.
- Isostasy, proposed by Clarence Edward Dutton in 1889, explains the balance of Earth's surface, where areas of the same size have the same mass underneath.
- Alfred Wegener proposed the Continental Drift Theory in 1915, suggesting continents were once joined and drifted apart.
The Breakup of Pangaea
- Permian Period (250 million years ago): All continents were joined as a supercontinent called Pangaea.
- Triassic Period (250-200 million years ago): Pangaea split into Laurasia (north) and Gondwana (south).
- Jurassic Period (200-145 million years ago): Laurasia and Gondwana continued to break apart.
- Cretaceous Period (145-66 million years ago): Continents moved closer to their current positions.
- Present Day: Continents continue to move due to Plate Tectonics.
Supercontinent Timeline
- Rodinia existed 1,100 million years ago, before Pangaea.
Types of Lithospheric Plates
- Continental Lithosphere: Thick, rigid slabs of rock making up Earth's continents, less dense than oceanic plates due to granitic composition.
- Oceanic Lithosphere: Thin, dense slabs of rock forming the ocean floor, composed of heavier basalt and gabbro rocks, generally younger than continental crust.
Plate Tectonics Theory
- Earth's outer shell, the Lithosphere, is fragmented into large and small plates.
- Asthenosphere is a semi-fluid layer beneath the Lithosphere.
- Plates move on the Asthenosphere like a jigsaw puzzle at rates from 1 to over 15 cm per year.
Mechanisms of Plate Tectonics
- Mantle Convection Theory: Heat in the mantle causes convection currents, which create a conveyor-belt-like movement, driving plate movement.
- Slab Pull Theory: Gravity and plate subduction drive tectonic movements, as denser plates sink into the mantle, pulling the rest of the plate with them.
Evidence of Plate Movement
- Paleontological Evidence: Similar fossils found on continents across the Atlantic suggest they were once connected, including those of Lystrosaurus, Cynognathus, and Glossopteris.
- Glacial Evidence: Glacial till deposits in the southern hemisphere align when continents are fit together, suggesting past glacier movement. Coal deposits in Antarctica indicate a warmer past climate.
- Paleoclimate Evidence: Rock types indicate past climate conditions, with glacial till near the poles and sand dunes/coral reefs pointing to desert/tropical climates.
- Paleomagnetism Evidence: Magnetic minerals show that Earth's poles have reversed many times, creating strips of normal and reversed polarities at mid-ocean ridges.
Earth's Interior
- Composed of 58 crustal plates with 15 major plates and 7 or 8 primary plates, the rest are smaller.
Primary Plates
- African Plate
- Eurasian Plate
- Indo-Australian Plate
- North American Plate
- Pacific Plate
- South American Plate
- Nazca Plate
Secondary Plates
- Arabian Plate
- Carribean Plate
- Cocos Plate
- Indian Plate
- Juan de Duca Plate
- Philippine Sea Plate
Plate Boundaries
- Plate boundaries are where two plates meet or diverge.
- Three types: Convergent, Divergent, and Transform.
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