Earth Science Chapter 9: Plate Tectonics

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Questions and Answers

What did Wegener's Continental Drift Hypothesis propose about the continents?

They drifted apart at a uniform speed since the beginning of Earth.

They were once part of a single supercontinent. (correct)

They have remained stationary since their formation.

They were formed independently without influence from each other.

Which of the following is a type of evidence Wegener used to support his hypothesis?

Global temperature variations over geological time.

Tectonic plate movements based on ocean currents.

Fossils of similar organisms found on different continents. (correct)

Uniform rock compositions across continents.

What is considered the uppermost layer of the Earth that behaves as a rigid layer in plate tectonics?

Outer core

Lithosphere (correct)

Mantle

Asthenosphere

What evidence supports continental drift through geological formations?

Mountain ranges that align across oceans. Signup and view all the answers

Why was Wegener's hypothesis initially rejected?

Wegener could not explain how continents moved. Signup and view all the answers

What is a significant advancement that led to the development of the plate tectonics theory?

Discovery of seafloor spreading. Signup and view all the answers

Which aspect of Earth's structure does the theory of plate tectonics primarily focus on?

The lithosphere and its movement. Signup and view all the answers

Which of these is NOT a type of evidence that supports Wegener's Continental Drift Hypothesis?

Observation of oceanic trench formations. Signup and view all the answers

What characterizes divergent boundaries in plate tectonics?

Plates move away from each other Signup and view all the answers

Which feature is primarily formed at convergent boundaries that involve oceanic and continental plates?

Volcanoes Signup and view all the answers

What happens at transform fault boundaries?

Lithosphere is neither created nor destroyed Signup and view all the answers

Which is an example of a continental rift?

East African Rift Valley Signup and view all the answers

How does seafloor spreading contribute to oceanic lithosphere formation?

By creating new oceanic crust at ridges Signup and view all the answers

In an oceanic-oceanic convergent boundary, what typically occurs?

One oceanic slab descends beneath the other Signup and view all the answers

What causes volcanic arcs on continents?

Subduction of oceanic lithosphere Signup and view all the answers

Which of the following types of boundaries does NOT involve the movement of plates toward each other?

Divergent boundaries Signup and view all the answers

Study Notes

Plate Tectonics Overview

Faults are fractures in the Earth's crust where movement has occurred.
Earthquakes are caused by the release of energy along faults.
Tsunamis occur due to underwater disturbances, such as earthquakes or volcanic eruptions.

Pangaea and Continental Drift

Continental Drift Hypothesis proposed by Alfred Wegener suggested that continents were once part of a supercontinent called Pangaea.
Pangaea began breaking apart approximately 200 million years ago, forming today's continents.

Evidence Supporting Continental Drift

Matching Fossils: Fossil organisms found on separate continents support the idea that they were once joined.
Rock Types and Structures: Similar mountain ranges and rock formations across different continents indicate prior connections.
Ancient Climate Evidence: Geological records suggest that ancient climates were similar across different continents at one time.

Wegener's Hypothesis and Its Limitations

Wegener's hypothesis faced skepticism due to the lack of a mechanism explaining how continents moved.
Advances in technology contributed to the development of the plate tectonics theory, providing a better understanding of continental movement.

Plate Tectonics Theory

The lithosphere, composed of the uppermost mantle and the crust, is a rigid layer that plays a significant role in tectonic activities.
Movements in the lithosphere lead to geological phenomena such as earthquakes, volcanic eruptions, and the creation of mountain ranges.

Continental Drift

A theory proposing continents were once joined and have drifted apart over time, previously thought to be rejected.
New theories emerge that challenge established concepts in geology.

Plate Tectonics

Division of the Earth's lithosphere into tectonic plates that interact at their boundaries.
Three main types of plate boundaries:
- Divergent Boundaries: Plates move apart, often associated with seafloor spreading.
- Convergent Boundaries: Plates move together, leading to subduction or continental collision.
- Transform Fault Boundaries: Plates slide past each other without lithosphere creation or destruction.

Actions at Plate Boundaries

Divergent Boundaries

Oceanic Ridges: Elevated zones found in all major ocean basins, where rift valleys form at their crests.
Rift Valleys: Deep faulted structures formed along divergent boundaries, can occur on seafloors or land (e.g., East African Rift Valley).
Seafloor Spreading: Process where new oceanic lithosphere is created, contributing to ocean basin formation.

Convergent Boundaries

Subduction Zones: Locations where one oceanic plate sinks beneath another, leading to volcanic activity and geological transformations.
- Oceanic-Continental: Denser oceanic slab subducts, forming volcanic arcs on continents (e.g., Andes, Cascades, Sierra Nevadas).
- Oceanic-Oceanic: Occurs when one oceanic plate descends beneath another, resulting in underwater volcanoes.

Examples of Convergent Boundaries

Oceanic-Continental: Example features include the Andes Mountains, which result from subduction-related volcanic activity.

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Description

Test your knowledge about the foundational concepts of Plate Tectonics as outlined in Chapter 9 of Prentice Hall's Earth Science by Tarbuck and Lutgens. Explore questions regarding faults, causes of earthquakes, and the formation of tsunamis. This quiz will help reinforce your understanding of these key geological processes.