Grade 7 Earth Science: Earth's Interior Exploration
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Questions and Answers

What geological evidence did Wegener use to support his theory of continental drift?

  • Earthquakes occurring simultaneously in multiple continents
  • Volcanic eruptions on separate landmasses
  • Rivers originating from the same mountain range
  • Glacial striations on different continents (correct)

    • What was one of the challenges faced by Wegener's theory of continental drift?

  • Inability to explain the forces behind continental movement (correct)
  • Overwhelming proof of the separation of continents
  • Lack of evidence of past climates preserved in rocks
  • Clear understanding of the composition of the ocean floor

    • What type of forces did Wegener propose as mechanisms for continental movement?

  • Magnetic forces and gravitational pull
  • Tidal forces and polar-fleeing forces (correct)
  • Centripetal forces and centrifugal forces
  • Convection forces and oceanic forces

    • Which type of geological formations in continents supported Wegener's theory due to signs of ancient glaciation?

    <p>Formations exhibiting striations from moving ice sheets</p> Signup and view all the answers

    What was the major limitation that hindered the widespread acceptance of continental drift in the scientific community?

    <p>Difficulty in explaining how continents could move through solid ocean floor</p> Signup and view all the answers

    What did the similar glacial striation patterns on continents separated by oceans suggest?

    <p>Shared glacial history on a single, larger landmass</p> Signup and view all the answers

    What did geological formations in continents like Africa, South America, India, and Australia show signs of?

    <p>Ancient glaciation</p> Signup and view all the answers

    What was one major reason why Wegener's theory faced skepticism within the scientific community?

    <p>Difficulty in explaining forces driving continental movement</p> Signup and view all the answers

    Why couldn't Wegener explain how continents could move through Earth's surface?

    <p>Unknown composition and structure of the ocean floor</p> Signup and view all the answers

    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.

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