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Questions and Answers
What happens to the ocean crust as it moves away from a mid-ocean ridge?
What happens to the ocean crust as it moves away from a mid-ocean ridge?
What is a key characteristic of subduction zones?
What is a key characteristic of subduction zones?
Which type of collisional feature forms when two continental plates collide?
Which type of collisional feature forms when two continental plates collide?
Which statement accurately highlights the relationship between divergent and convergent boundaries?
Which statement accurately highlights the relationship between divergent and convergent boundaries?
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How does lithosphere thickness change relative to a mid-ocean ridge?
How does lithosphere thickness change relative to a mid-ocean ridge?
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What evidence supports the theory of moving plates?
What evidence supports the theory of moving plates?
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What occurs at mid-ocean ridges?
What occurs at mid-ocean ridges?
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Which type of crust is primarily associated with oceanic plates?
Which type of crust is primarily associated with oceanic plates?
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How does the distribution of earthquakes relate to plate tectonics?
How does the distribution of earthquakes relate to plate tectonics?
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What happens to old ocean crust at deep-sea trenches?
What happens to old ocean crust at deep-sea trenches?
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What is a common feature of divergent plate boundaries?
What is a common feature of divergent plate boundaries?
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Which layer of the Earth is broken into tectonic plates?
Which layer of the Earth is broken into tectonic plates?
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What geological activity is primarily associated with transform plate boundaries?
What geological activity is primarily associated with transform plate boundaries?
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What was the main hypothesis proposed by Alfred Wegener in 1915?
What was the main hypothesis proposed by Alfred Wegener in 1915?
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How did Wegener support his theory of Continental Drift regarding the continents?
How did Wegener support his theory of Continental Drift regarding the continents?
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What does the 'Bullard fit' refer to in Wegener’s theory?
What does the 'Bullard fit' refer to in Wegener’s theory?
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Why did some scientists oppose Wegener's ideas?
Why did some scientists oppose Wegener's ideas?
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What significant advancement in plate tectonic theory occurred after WWII?
What significant advancement in plate tectonic theory occurred after WWII?
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Which piece of evidence did Wegener NOT use to support his hypothesis?
Which piece of evidence did Wegener NOT use to support his hypothesis?
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How did Wegener describe the configuration of continents in his model?
How did Wegener describe the configuration of continents in his model?
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Which of the following best describes Wegener's ability to address geological similarities between continents?
Which of the following best describes Wegener's ability to address geological similarities between continents?
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Study Notes
Wegener's Theory of Continental Drift
- German meteorologist Alfred Wegener proposed the theory of Continental Drift in 1915.
- Wegener suggested that all the continents were once joined together in a supercontinent called Pangaea.
- Wegener's theory was largely rejected during his lifetime.
- Wegener used evidence from various fields to support his theory.
Evidence for Wegener's Theory
- Matching Coast Lines: Wegener noted that the coastlines of continents, particularly South America and Africa, fit together like puzzle pieces. This observation supported the concept of a single landmass that had broken apart.
- Fossil Evidence: Wegener noted similar types of fossils found on different continents separated by vast oceans. The presence of identical fossils on continents now far apart suggested that they were once connected.
- Ancient Climate Belts: Wegener observed that similar ancient climate belts, such as glacial deposits and warm climate fossils, corresponded across different continents. This supported the idea they were once connected and part of a single landmass.
- Matching Geologic Units: Wegener identified matching geological formations (rocks, structures, and mountain ranges) on separate continents, further supporting the idea of a once continuous landmass.
Opposition to Wegener's Theory
- Wegener's theory was met with opposition from the scientific community.
- The main objection was the lack of a plausible mechanism to explain how continents could move across Earth's surface.
- Wegener proposed that continents moved through the oceanic crust, a concept that was not supported by the limited knowledge of the Earth's interior at that time.
Harry Hess and Seafloor Spreading
- American professor Harry Hess proposed the theory of seafloor spreading in 1960.
- Hess proposed that new oceanic crust is formed at mid-ocean ridges.
- As new crust is formed, the old crust is pushed away from the ridge and eventually descends into deep trenches.
- This process, known as subduction, destroys old crust.
Evidence for Seafloor Spreading
- Bathymetry: The discovery of deep-sea trenches, mid-ocean ridges, and other bathymetric features provided evidence for seafloor spreading.
- Earthquake Distribution: Earthquakes did not occur randomly but were concentrated along specific belts, primarily around the mid-ocean ridges and deep trenches.
- Paleomagnetism: Evidence from the magnetic properties of rocks on the ocean floor supported seafloor spreading.
Modern Plate Tectonics Theory
- The theory of plate tectonics emerged as a synthesis of Continental Drift and seafloor spreading.
- Plate tectonics proposed that Earth's outer layer is broken into a series of rigid plates called lithospheric plates.
- The plates move relative to each other, and their interactions are responsible for major geological phenomena like earthquakes, volcanic eruptions, and mountain building.
Lithospheric Plates
- Earth's lithosphere is divided into about 20 major plates, each containing both oceanic and continental crust.
- The plates move over a semi-molten layer called the asthenosphere.
Identifying Plate Boundaries
- Plate boundaries are zones where the plates interact, resulting in geological activity.
- Active faults, which are fractures in the Earth's crust where movement has occurred, are often found along plate boundaries.
- Earthquakes often occur along active faults, providing evidence for ongoing plate movement.
Types of Plate Boundaries
- Divergent Boundaries: Plates move apart, allowing magma to rise from the asthenosphere, forming new crust. These zones are characterized by features like mid-ocean ridges and volcanic activity.
- Convergent Boundaries: Plates collide, leading to one plate being forced beneath the other (subduction). Convergent boundaries are associated with deep-sea trenches, volcanic arcs, and mountain building.
- Transform Boundaries: Plates slide past each other horizontally, causing earthquakes along fault lines like the San Andreas Fault.
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Description
Explore Alfred Wegener's groundbreaking theory of Continental Drift, proposed in 1915, which suggested that continents were once part of a supercontinent called Pangaea. The quiz examines the evidence Wegener provided, such as matching coastlines, fossil similarities, and ancient climate patterns to support his ideas. Test your knowledge about this pivotal concept in geology!
