Sea Floor Spreading Flashcards

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Questions and Answers

What are the underwater mountains called?

  • Trenches
  • Oceanic valleys
  • Mid ocean ridges (correct)
  • Continental shelves

How did scientists determine the location and size of underwater mountain chains?

Sonar

How do mid ocean ridges form?

Convection currents bring molten material up to the upper mantle, rising through fault cracks between diverging oceanic plates.

Where do mid ocean ridges form?

<p>Along divergent boundaries in every part of the world's ocean.</p> Signup and view all the answers

Who was Harry Hess and what did he study?

<p>He was an American geologist who studied mid ocean ridges.</p> Signup and view all the answers

What radical idea did Hess propose?

<p>He proposed the process of sea floor spreading.</p> Signup and view all the answers

Where does sea floor spreading begin?

<p>At the mid ocean ridge.</p> Signup and view all the answers

What happens to oceanic crust at deep ocean trenches?

<p>It eventually sinks back into the mantle.</p> Signup and view all the answers

What is this process called?

<p>Subduction</p> Signup and view all the answers

What force pulls oceanic crust down beneath the trench?

<p>Gravity</p> Signup and view all the answers

Explain the process of sea floor spreading.

<p>Sea floor spreading occurs when the sea floor spreads apart along divergent boundaries, forming the mid ocean ridge. Magma rises through cracks and hardens, forming new crust on both sides.</p> Signup and view all the answers

How does sea floor spreading support the idea of continental drift?

<p>Magma thrusts up and hardens forming new crust, causing the ocean floor to move outward and carry continents along.</p> Signup and view all the answers

What technologies helped Hess prove his theory of sea floor spreading?

<p>Sonar, submarines, tools for deeper oceanic drilling.</p> Signup and view all the answers

What happens to the rock when oceanic crust is formed?

<p>Old rock is pushed out under the ridge.</p> Signup and view all the answers

What is this process called?

<p>Subduction</p> Signup and view all the answers

What happens to oceanic crust at deep ocean trenches?

<p>It eventually sinks back into the mantle.</p> Signup and view all the answers

Every __________ (___________) years, new rock forms at the mid ocean ridge and sinks into a trench recycling itself.

<p>200 million (200,000,000)</p> Signup and view all the answers

Why is the Pacific Ocean shrinking?

<p>Subduction is occurring faster than new crust is being added.</p> Signup and view all the answers

What are the three kinds of tectonic plates?

<p>All of the above (D)</p> Signup and view all the answers

These different types of boundaries occur on land and in the ocean all around the world. You should be able to use symbols provided to identify the different types of boundaries such as: a. ________________ between the Eurasian and Pacific Plates.

<p>Convergent boundaries</p> Signup and view all the answers

What landforms are created when two ocean plates diverge? _____________.

<p>Mid-ocean ridges, mountain ranges, central valley.</p> Signup and view all the answers

What landforms are created when two continental plates diverge? _____________.

<p>Rift valley, volcanoes.</p> Signup and view all the answers

What landforms are created when an oceanic and a continental plate converge? _____________.

<p>Subduction zones, volcanic islands, trenches.</p> Signup and view all the answers

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Study Notes

Mid-Ocean Ridges

  • Underwater mountain chains are known as mid-ocean ridges.
  • Form along divergent boundaries where tectonic plates pull away from each other.
  • Found in every ocean around the globe.

Sea Floor Spreading

  • Occurs at mid-ocean ridges where magma rises from the mantle, creating new oceanic crust.
  • The process supports continental drift, as new crust formation pushes adjacent crust outward.
  • Takes place approximately every 200 million years as new rock forms, moves, and sinks into trenches.

Key Figures and Proposals

  • Harry Hess was an American geologist who studied mid-ocean ridges and proposed the concept of sea floor spreading.
  • Hess's radical idea suggested that new crust is continually added, affecting plate movement.

Mechanisms of Oceanic Crust

  • Oceanic crust sinks back into the mantle at deep ocean trenches through a process called subduction.
  • The force of gravity pulls the crust down into these trenches.

Technologies Advancing Study

  • During Hess's lifetime, advancements such as sonar, submarines, and deep ocean drilling tools emerged, aiding in the proof of sea floor spreading.
  • These technologies were pivotal in understanding oceanic structures, unlike during Wegener's time.

Tectonic Plates and Boundaries

  • There are three primary types of tectonic plate boundaries:
    • Convergent boundaries (plates move towards each other)
    • Divergent boundaries (plates move apart)
    • Transform boundaries (plates slide past each other)
  • Examples of boundaries include:
    • Convergent: Eurasian and Pacific Plates
    • Divergent: North American and Eurasian Plates
    • Transform: Sections of North American and Pacific Plates.
  • Diverging ocean plates create mid-ocean ridges and mountain ranges.
  • Diverging continental plates form rift valleys and volcanoes.
  • Converging oceanic and continental plates lead to subduction zones and volcanic islands.

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