Plate Tectonics Overview

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Questions and Answers

What was Alfred Wegener's primary proposition regarding the continents?

Continents are constantly forming and disappearing.

Continents are fixed and do not move.

Continents move around on Earth's surface and were once joined. (correct)

Continents only move vertically.

What is the term Wegener used to describe the supercontinent he proposed?

Atlantis

Superterra

Gondwana

Pangaea (correct)

What specific piece of evidence did Wegener use to support his supercontinent hypothesis?

The varying magnetic fields measured across the continents.

The existence of active volcanoes in different locations on Earth

The presence of different rock types on separate continents.

The fitting of continents together like a puzzle, particularly the Americas and Africa. (correct)

Which type of evidence did Wegener NOT use to support his continental drift hypothesis?

Differences in ocean depths between continents. (C) Signup and view all the answers

What did Wegener suggest about the fossils found on different continents?

The organisms lived side-by-side before the continents separated. (C) Signup and view all the answers

What was the main reason why scientists did not believe Wegener during his lifetime?

They did not believe continents could move. (B) Signup and view all the answers

Why are the edges of the continental shelf considered the 'true' size and shape of a continent?

They include the surrounding shallow ocean floor that is part of the continent. (B) Signup and view all the answers

What was the name given to Wegener's hypothesis regarding the movement of continents?

Continental Drift (C) Signup and view all the answers

Which of the following best describes Wegener's explanation for the presence of Glossopteris fossils on multiple continents?

The continents were once joined, and the fossils were distributed across them before they moved. (D) Signup and view all the answers

Why did the discovery of Mesosaurus fossils on different continents support Wegener's continental drift theory?

Mesosaurus was a freshwater reptile, and the continents must have been joined to share fresh water habitats. (C) Signup and view all the answers

How did ancient glacial evidence on multiple continents, far from the poles, support Wegener's theory of continental drift?

It suggested that the continents were all once joined near the South Pole and that the glaciers later moved with the landmasses. (B) Signup and view all the answers

What was the primary reason that Wegener's theory of continental drift was rejected by most geologists of his time?

Wegener lacked a plausible mechanism to explain how continents could move through oceanic crust. (C) Signup and view all the answers

The discovery of seafloor spreading provided a mechanism for continental drift. Which of the following best describes this mechanism?

New oceanic crust is created at mid-ocean ridges and destroyed at deep-sea trenches, moving the continents with it. (C) Signup and view all the answers

What type of technology did scientists use during World War II that led to the discovery of seafloor spreading?

Echo sounders used on ships to locate enemy submarines. (C) Signup and view all the answers

What did scientists learn from the echo sounder data collected during World War II?

The exact depth and shape of the ocean bottom. (B) Signup and view all the answers

Based on his theory, what did Wegener say about ancient coral reefs and coal deposits?

They were once located in warm, tropical regions and then drifted to colder regions. (C) Signup and view all the answers

What primary feature is revealed by bathymetric maps of the ocean floor?

A large chain of mountains known as mid-ocean ridges (D) Signup and view all the answers

Which of the following best describes the pattern of magnetic polarity observed on the seafloor?

Alternating stripes of normal and reversed polarity, mirrored on either side of mid-ocean ridges. (D) Signup and view all the answers

According to the provided information, how does sediment thickness change with distance from a mid-ocean ridge axis?

Sediment thickness increases farther from the axis. (B) Signup and view all the answers

The oldest seafloor crust is typically found where?

Near margins of continents or deep sea trenches (B) Signup and view all the answers

What is one key observation that led scientists to conclude that seafloor is being destroyed?

The relatively young age of the oldest seafloor compared to continental crust. (B) Signup and view all the answers

According to the seafloor spreading hypothesis, what is the main cause for the uplift of mid-ocean ridges?

The rising of hot, buoyant mantle material. (C) Signup and view all the answers

How does crust thickness change with distance from a mid-ocean ridge axis?

Crust thickness is thinnest at the axis, and increases further away. (C) Signup and view all the answers

How does heat flow change with distance from a mid-ocean ridge axis?

Heat flow is highest at the ridge axis and decreases away. (B) Signup and view all the answers

What geological feature is formed primarily as a result of oceanic-to-oceanic convergence?

Volcanic islands (D) Signup and view all the answers

Which of the following mountain ranges was formed due to continental-to-continental convergence?

Himalayan Mountains (B) Signup and view all the answers

What is the primary process that occurs during continental-to-continental convergence?

Folding and faulting (C) Signup and view all the answers

What significant event was caused by the collision of two continental plates in India in 2005?

An earthquake (C) Signup and view all the answers

Which fault is recognized as a prominent transform plate boundary?

San Andreas Fault (C) Signup and view all the answers

What type of geological activity takes place at intraplate boundaries?

Hotspot formation (D) Signup and view all the answers

Which of the following best describes the interaction at transform plate boundaries?

Plates slide past each other (C) Signup and view all the answers

What is the rate of movement of the Pacific plate at the San Andreas Fault?

3 inches per year (A) Signup and view all the answers

What happens to lava when it erupts at the ridge?

It cools to form magnetite crystals that capture magnetic polarity. (A) Signup and view all the answers

How does oceanic crust influence the movement of continents?

It pushes continents away from the ridge axis. (C) Signup and view all the answers

What do scientists use to locate earthquake epicenters?

Seismograph networks set up during the Cold War. (C) Signup and view all the answers

What portion of the Earth is responsible for the movement of tectonic plates?

The lithosphere. (D) Signup and view all the answers

What is the typical rate of movement for tectonic plates?

A few centimeters per year. (D) Signup and view all the answers

What geological structures define the boundaries of tectonic plates?

Mid-ocean ridges and deep sea trenches. (D) Signup and view all the answers

Which statement best describes the relationship between continental drift and seafloor spreading?

Seafloor spreading is a mechanism explaining continental drift. (A) Signup and view all the answers

What is the composition of tectonic plates?

A combination of both oceanic and continental lithosphere. (A) Signup and view all the answers

What is the primary reason hotspot volcanoes are found in a line?

They move with tectonic plates over a stationary hotspot. (B) Signup and view all the answers

Which statement accurately describes the age of volcanoes in a hotspot chain?

Volcanoes become older with distance from the hotspot. (D) Signup and view all the answers

What geological feature is formed at a convergent plate boundary?

Mountain ranges like the Appalachian Mountains. (C) Signup and view all the answers

Why do hotspot magmas rarely penetrate thick continental crust?

Thick crust obstructs their path. (B) Signup and view all the answers

Which mountain range is primarily composed of granitic intrusions?

Sierra Nevada. (D) Signup and view all the answers

What evidence did Wegener use to support his continental drift hypothesis?

The similarity of mountains on opposing sides of the Atlantic. (C) Signup and view all the answers

What is the current trend in the Pacific and Atlantic oceans?

The Pacific is shrinking while the Atlantic is growing. (C) Signup and view all the answers

What is the geologic origin of the Cascades Range?

They are a result of oceanic plate subduction. (C) Signup and view all the answers

Study Notes

Plate Tectonics

Plate tectonics is the theory that Earth's surface is broken into large, rigid plates that move relative to each other.
Alfred Wegener proposed the theory of continental drift, suggesting continents move over Earth's surface.
Evidence for continental drift includes matching coastlines, similar rock types, and fossils on different continents.
Seafloor spreading is a process where new oceanic crust forms at mid-ocean ridges, pushing older crust away.
Magnetic stripes on the seafloor provide evidence for seafloor spreading, showing alternating periods of normal and reversed magnetic polarity.
Earth's plates are composed of the lithosphere, which includes the crust and upper mantle.
Plates move due to convection currents in the Earth's mantle.
Plate boundaries are the edges where tectonic plates meet.
Divergent boundaries occur where plates move apart, creating new crust.
Convergent boundaries occur where plates move together, leading to subduction or mountain building.
Transform boundaries occur where plates slide past each other horizontally.
Volcanic eruptions and earthquakes are common at plate boundaries.
Continents and oceans can form and disappear as a result of plate movement over millions of years.
Mid-ocean ridges are underwater mountain ranges where new crust is formed.
Deep sea trenches are deep depressions in the ocean floor where crust is subducted.
The process of subduction occurs when an oceanic plate sinks beneath a continental or another oceanic plate.
Mountains form when continental plates collide at convergent boundaries.
Intraplaate activity, or geological activity within a plate, can occur from mantle plumes and hotspots.
Mantle plumes are columns of hot, rising mantle material.
Hotspots remain stationary while plates move over them, creating volcanic chains.
The Yellowstone hotspot is an example of an intraplate volcanic region.
Plate tectonics explains many geological features on Earth.

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Description

This quiz covers the fundamental concepts of plate tectonics, including Alfred Wegener's theory of continental drift and evidence supporting it. Learn about seafloor spreading, plate boundaries, and the lithosphere's composition. Test your knowledge on how Earth's plates interact and the processes driving their movement.