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Questions and Answers
What geological evidence did Wegener use to support his theory of continental drift?
What was one of the challenges faced by Wegener's theory of continental drift?
What type of forces did Wegener propose as mechanisms for continental movement?
Which type of geological formations in continents supported Wegener's theory due to signs of ancient glaciation?
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What was the major limitation that hindered the widespread acceptance of continental drift in the scientific community?
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What did the similar glacial striation patterns on continents separated by oceans suggest?
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What did geological formations in continents like Africa, South America, India, and Australia show signs of?
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What was one major reason why Wegener's theory faced skepticism within the scientific community?
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Why couldn't Wegener explain how continents could move through Earth's surface?
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Study Notes
Earth's Interior Exploration
- Earth's interior is inaccessible directly, with only 12 kilometers (7.6 miles) reached through drilling.
- The Earth's radius is approximately 6,371 kilometers (3,959 miles).
- Seismic waves, produced by earthquakes and volcanic activities, serve as the primary tool for exploring Earth's interior.
- The speed and behavior of seismic waves depend on material density and composition, revealing the hidden structures of the planet.
- Scientists use seismic tomography to create a three-dimensional model of Earth's interior, similar to a CT scan for medical imaging.
Earth's Structure
- The Earth consists of several layers: crust, mantle, outer core, and inner core.
- The crust is the thinnest layer, measuring between 5 and 70 kilometers in thickness.
- The mantle is the thickest layer, stretching to about 2,900 kilometers beneath the crust.
- The outer core is a liquid layer, approximately 2,300 kilometers thick, mainly composed of molten iron and nickel.
- The temperature of the outer core ranges from 4,500°C to 5,500°C (8,132°F to 9,932°F).
Core Composition
- Inner core is solid, with a radius of about 1,220 kilometers, composed of solid iron and nickel.
- Despite inner core temperatures exceeding 5,400°C (9,800°F), extreme pressure (3 million times atmospheric pressure) keeps it solid.
- Some theories suggest the existence of an "inner-inner core" that may be even hotter and deeper.
Plate Tectonics & Continental Drift
- The flowing asthenosphere within the mantle drives continental drift, tectonic plate movement, and volcanic activity.
- Alfred Wegener introduced the theory of continental drift, suggesting continents were once part of a supercontinent called Pangaea that began to break apart roughly 175 million years ago.
- Pangaea, named from the Greek words “pan” (universal) and “gea” (land), existed from the early Paleozoic era through the Mesozoic period.
Evidence Supporting Continental Drift
- Continental Fit: Coastlines of continents like South America and Africa resemble a jigsaw puzzle, indicating they were once joined.
- Fossil Evidence: Identical fossils found on separate continents suggest they were once connected, allowing species to roam freely.
- Geologic Features: Geological formations, such as mountain ranges, show similarities across continents, indicating they were part of a single landmass.
Further Implications
- If Pangaea had never broken apart, the current arrangement and ecosystems of continents would be profoundly different.
- Ongoing studies about the Earth's layers and movements contribute to our understanding of geology and planetary dynamics.
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Description
Explore how scientists use seismic waves to study the hidden layers beneath Earth's surface in this Grade 7 Earth Science quiz. Learn about the tools and methods used to map the Earth's interior beyond the crust.
