Seafloor Spreading Flashcards

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Questions and Answers

What is the definition of Mid-Ocean Ridge?

  • The process by which oceanic crust sinks beneath a trench
  • A deep valley along the ocean floor
  • An undersea mountain chain where new ocean floor is produced (correct)
  • A device that determines the distance of an object underwater

What is the purpose of a Sonar?

A device that determines the distance of an object underwater by recording echoes of sound waves.

What is Seafloor Spreading?

The process by which molten materials add new oceanic crust to the ocean floor.

What is a Deep Ocean Trench?

<p>A deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle.</p> Signup and view all the answers

What is subduction?

<p>The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent boundary.</p> Signup and view all the answers

When were the ocean floors mapped and what was the tool used?

<p>In the 1960's, the ocean floor was mapped by using the device Sonar.</p> Signup and view all the answers

Who proposed the Seafloor Spreading theory and when?

<p>In 1960, Harry Hess proposed the theory of Seafloor Spreading.</p> Signup and view all the answers

What are the steps in the process of Seafloor Spreading?

<ol> <li>The seafloor spreads apart along both sides of the mid-ocean ridge. 2. New crust is added.</li> </ol> Signup and view all the answers

What is the evidence for Seafloor Spreading?

<ol> <li>Evidence from Molten Material. 2. Evidence from Magnetic Stripes. 3. Evidence from Drilling Samples.</li> </ol> Signup and view all the answers

What happens at deep ocean trenches?

<p>Part of the ocean floor sinks back to the mantle.</p> Signup and view all the answers

Describe a Mid-Ocean Ridge.

<p>A Mid-Ocean Ridge is a contiguous range of mountains.</p> Signup and view all the answers

Describe the process of Seafloor Spreading.

<p>Magma squeezes up through cracks between the plates and hardens to form new rock. Newer eruptions push older rocks away from the ridge.</p> Signup and view all the answers

What happens to old oceanic crust as new molten material rises from the mantle?

<p>The oceanic crust is being subducted into the mantle.</p> Signup and view all the answers

What are three types of evidence found to support the idea of the ocean floor spreading away from the ridge?

<p>Evidence from molten material, magnetic stripes, and drilling samples.</p> Signup and view all the answers

Why does subduction occur?

<p>Subduction occurs because as new rocks form, older rocks sink back into the mantle.</p> Signup and view all the answers

Flashcards

Mid-Ocean Ridge

A continuous underwater mountain range where new oceanic crust forms.

Seafloor Spreading

The process where new oceanic crust is created at mid-ocean ridges, pushing older crust away.

Sonar

Technology using sound waves to map underwater distances.

Deep Ocean Trench

A valley on the ocean floor where oceanic crust dives back into the mantle.

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Subduction

The process of oceanic crust sinking into the mantle at convergent plate boundaries.

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Oceanic Crust

The rock that makes up the ocean floor.

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Magnetic Stripes

Patterns in magnetized rocks on the ocean floor showing changes in Earth's magnetic field.

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Molten Material

Liquid rock, rising through the mantle and solidifying into new crust.

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Harry Hess

Scientist who introduced the theory of seafloor spreading in 1960.

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Mapping Ocean Floors

Using Sonar to create detailed maps of the ocean floor.

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New Crust Formation

The creation of new rock at mid-ocean ridges.

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Old Crust Age

Further away from mid-ocean ridges, the older the crust.

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Drilling Samples

Collecting samples from the ocean floor for analysis to study the ocean's crust.

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Tectonic Activity

The movement of tectonic plates that causes processes like seafloor spreading and subduction

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Study Notes

Seafloor Spreading Key Concepts

  • Mid-Ocean Ridge: A continuous undersea mountain range where new oceanic crust is created.
  • Sonar: A technology utilized to measure underwater distances by analyzing sound wave echoes.

Processes and Mechanisms

  • Seafloor Spreading: Involves the addition of new oceanic crust from molten rock material at mid-ocean ridges.
  • Deep Ocean Trench: A significant ocean floor valley where oceanic crust submerges back into the mantle.
  • Subduction: The descending of oceanic crust beneath a trench at convergent tectonic plate boundaries.

Historical Context

  • Mapping Ocean Floors: Conducted in the 1960s using Sonar technology to create detailed maps of underwater topography.
  • Theory Proposal: Harry Hess introduced the theory of Seafloor Spreading in 1960.

Steps in Seafloor Spreading

  • The ocean floor expands at mid-ocean ridges, creating new crust on either side.
  • Newly formed crust pushes older rocks away from the ridge.

Evidence Supporting Seafloor Spreading

  • Molten Material: Evidence is found in submarine volcanic rocks, which solidify rapidly after underwater eruptions.
  • Magnetic Stripes: Ocean floor rocks exhibit a pattern of magnetized stripes, indicating changes in Earth's magnetic field over time.
  • Drilling Samples: Samples taken further from mid-ocean ridges show increased age, supporting the theory of spreading.

Oceanic Crust Dynamics

  • Old Crust Behavior: As new molten material rises, the older oceanic crust undergoes subduction into the mantle.

Descriptions and Functions

  • Mid-Ocean Ridge Description: Features a continuous range of underwater mountains formed by tectonic activity.
  • Seafloor Spreading Process: Involves magma rising through cracks, solidifying to create new rock, which then pushes older rocks outwards.

Rationale for Subduction

  • Subduction is driven by the formation of new rocks at mid-ocean ridges, causing older rock sections to sink back into the mantle.

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