Tectonic Plates and Divergent Boundaries
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Questions and Answers

What are tectonic plates primarily composed of?

  • Rocks that form the lithosphere (correct)
  • Sedimentary soil
  • Liquid magma
  • Frozen water

Which layer of the Earth is cooler and more rigid?

  • Lithosphere (correct)
  • Outer core
  • Inner core
  • Asthenosphere

What defines a divergent plate boundary?

  • Plates are splitting due to seismic activity
  • Plates are sliding past each other without creating new crust
  • Plates are colliding and mountains are formed
  • Plates are pulling apart and new lithosphere is created (correct)

What process occurs at mid-ocean ridges?

<p>Creation of new lithosphere (A)</p> Signup and view all the answers

What is the primary driving mechanism behind the movement of tectonic plates in the asthenosphere?

<p>Convection currents (C)</p> Signup and view all the answers

What type of stress is associated with divergent boundaries?

<p>Tensional stress (A)</p> Signup and view all the answers

What is the term for the fractures in the crust that form due to tectonic stress?

<p>Faults (D)</p> Signup and view all the answers

During seafloor spreading, what happens after new lava solidifies?

<p>It fractures due to extensional stress (D)</p> Signup and view all the answers

What process occurs when a continent splits into two divergent continents?

<p>Continental rifting (C)</p> Signup and view all the answers

What evidence supports the theory of seafloor spreading?

<p>Maps of earthquake distributions (D)</p> Signup and view all the answers

What is the main reason why oceanic crust sinks deeper into the mantle compared to continental crust?

<p>Oceanic crust is richer in iron and more dense (B)</p> Signup and view all the answers

How do pillow basalts form?

<p>From magma cooling rapidly in water (C)</p> Signup and view all the answers

What primarily causes the uplift of mountain ranges at collision zones?

<p>Deformation of crust (D)</p> Signup and view all the answers

What is the role of the asthenosphere in continental rifting?

<p>It melts to form magma (A)</p> Signup and view all the answers

Why are many mountain ranges predominantly linear?

<p>They result from continent-continent collisions (D)</p> Signup and view all the answers

What happens to marine sediment thickness as distance from the mid-ocean ridge increases?

<p>It becomes thicker (A)</p> Signup and view all the answers

What geologic process primarily causes the formation of mountains in continental-continental collision zones?

<p>Thrust faulting due to compressional stress (A)</p> Signup and view all the answers

Which of the following is true about oceanic-continental subduction zones?

<p>They result in the oceanic lithosphere diving beneath continental crust. (A)</p> Signup and view all the answers

How does the melting snow from high mountains influence the surrounding environment?

<p>It provides melt water for ecosystems and human consumption. (C)</p> Signup and view all the answers

What is the primary force acting along transform plate boundaries?

<p>Shear (C)</p> Signup and view all the answers

What phenomenon is responsible for creating hot spot trails?

<p>Movement of tectonic plates over a stationary mantle plume (A)</p> Signup and view all the answers

What is the elastic rebound theory in relation to earthquakes?

<p>It describes the release of stored energy in rocks during fault movement. (A)</p> Signup and view all the answers

Which term describes the gap or weakness between two fault blocks?

<p>Fault line (B)</p> Signup and view all the answers

What happens at a continental-oceanic boundary during a subduction event?

<p>The oceanic plate sinks, and magma is generated. (D)</p> Signup and view all the answers

What phenomenon describes the behavior of faults that can lead to an earthquake?

<p>Stick-slip behavior (C)</p> Signup and view all the answers

Which type of seismic wave travels the fastest during an earthquake?

<p>Primary waves (B)</p> Signup and view all the answers

How do subduction zone earthquakes typically trigger tsunamis?

<p>By displacing the ocean floor (B)</p> Signup and view all the answers

What characteristic of tsunamis allows them to travel across the ocean with minimal energy loss?

<p>Long wavelength (D)</p> Signup and view all the answers

What is the primary function of an earthquake early warning system?

<p>To alert people before seismic waves arrive (A)</p> Signup and view all the answers

Which type of plate boundary is characterized by two tectonic plates moving apart?

<p>Divergent boundary (D)</p> Signup and view all the answers

What type of volcano is primarily formed from low-silica magma and produces gentle eruptions?

<p>Shield volcano (B)</p> Signup and view all the answers

What process is commonly associated with the movement of tectonic plates at a transform boundary?

<p>Shear stress (B)</p> Signup and view all the answers

Flashcards

Tectonic Plates Composition

Tectonic plates are made of the Earth's lithosphere, which is the cool, strong, rigid crust and upper mantle.

Divergent Plate Boundary

A divergent plate boundary is where tectonic plates move apart, creating new lithosphere.

Divergent Boundary Location

Divergent plate boundaries are often found at mid-ocean ridges and continental rifts.

Seafloor Spreading

Seafloor spreading is the process of creating new oceanic lithosphere at mid-ocean ridges.

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Mid-Ocean Ridge

A mid-ocean ridge is a long chain of underwater mountains formed by magma rising to the surface and creating new oceanic crust.

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Tectonic plates motion

Tectonic plates are in constant motion and deformation over large scales and long periods of time.

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Asthenosphere

The asthenosphere is the upper mantle, hot, weak, plastic layer below the lithosphere that allows plate movement.

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Extensional Stress

Extensional stress occurs when forces pull plates apart, causing stretching and thinning.

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Seafloor Spreading Evidence

Seafloor spreading is supported by observations of seafloor features, sediment thickness, earthquake patterns, heat flow, and exploration of mid-ocean ridges.

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Continental Rifting

Continents can break apart because of mantle upwelling causing stretching and faulting, leading to magma creation and volcanism at divergent boundaries.

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Continental vs. Oceanic Crust Density

Oceanic crust is denser than continental crust, causing the continental crust to float higher, creating elevated landmasses and deeper ocean basins.

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Mountain Formation

Mountains are formed when continents collide, causing deformation and uplift.

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Convergent Plate Boundaries

When tectonic plates collide, leading to different mountain ranges and geological features.

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Fissure Eruptions

Effusive eruptions occur along fissures in mid-ocean ridges, leading to pillow basalt formation.

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Continental Collision

When two continental plates collide, causing intense deformation and uplift, forming mountain ranges.

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Continental-Continental Collision

When two continental plates collide, they have similar densities and neither is subducted. This causes intense uplift, creating mountain ranges like the Himalayas and the Alps.

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Collision Zone Formation

Collision zones form when tectonic plates with similar densities collide. The pressure forces the crust upward, leading to the creation of mountains and other geological features.

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Thrust Faulting

A type of fault where rocks are pushed over one another, creating large-scale deformation and mountain uplift. It's common in collision zones and areas of compressional stress.

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Subduction Zone Components

Subduction zones comprise a variety of geological features, including: the trench where the denser plate sinks, the volcanic arc above the subducting plate, and the accretionary prism where sediment is scraped off the subducting plate.

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Volcanic Activity and Subduction

Volcanic activity is a key feature of subduction zones. The subducting plate releases water as it sinks, which melts the surrounding mantle, creating magma that rises to the surface and erupts.

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Elastic Rebound Theory

This theory explains how earthquakes occur. Rocks along a fault store energy as they are deformed, until the stress overcomes the rock's strength, causing a sudden release of energy in the form of an earthquake.

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Mantle Plumes and Hot Spots

Mantle plumes are columns of hot rock rising from deep within the Earth's mantle. They can create volcanic activity at the surface, even in the middle of tectonic plates, forming ‘hot spots’.

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Sea Mounts and Atolls

Sea mounts are underwater mountains often formed by volcanic activity. As they erode and sink below sea level, coral reefs can grow around them, forming atolls which are ring-shaped islands.

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Stick-Slip Behavior

A process where rocks along a fault build up stress, then suddenly slip, releasing energy as an earthquake. This cycle of stress build-up and sudden release is repeated.

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Earthquake Cycle

The repeated cycle of stress accumulation, followed by sudden release during earthquakes, leading to a period of relative quiet until the cycle starts again.

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Types of Seismic Waves

There are four main types: P-waves (primary), S-waves (secondary), surface waves (Love and Rayleigh), each with different speeds and motion, causing varying ground shaking.

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Tsunami Trigger

Subduction zone earthquakes, where one tectonic plate slides under another, can displace massive amounts of water, generating large waves called tsunamis.

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Tsunami Traits

Tsunamis travel across vast oceans at high speeds, but appear as a slow rise in water level on the coast, eventually causing devastating flooding.

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Earthquake Early Warning

Systems that detect the initial P-waves of an earthquake and send alerts before the stronger S-waves and surface waves arrive, giving people time to react.

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Continental Drift

The theory that continents have moved over Earth's surface throughout geologic time, once forming a supercontinent called Pangaea.

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Plate Tectonics

The theory explaining Earth's surface movement due to the interaction of large, rigid plates that move, collide, and separate, shaping continents and oceans.

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Study Notes

Tectonic Plates

  • Tectonic plates are composed of rock, shaped like slabs, forming Earth's outer surface
  • Geologic boundaries (earthquakes, volcanoes, and seafloor features) often do not coincide with continental boundaries
  • Tectonics involve large-scale, slow-motion movement and deformation
  • Lithosphere encompasses the crust and upper mantle (approximately 100 km deep)
  • It's cool, strong, and rigid
  • Asthenosphere is the upper mantle, ranging from 400-600 km deep
  • It's hot and plastic-like, with different strengths compared to the lithosphere
  • It flows by convection

Divergent Plate Boundaries

  • Marked by mid-ocean ridges and continental rifts
  • Characterized by extensional stress
  • Seafloor spreading creates new lithosphere
  • Magma wells up, emerging onto the seafloor
  • Rift valleys/axial rift form
  • Plates pull apart along an axis, causing brittle crust to fracture along ridges and faults
  • Faults are planes of weakness where rock breaks, and abrupt movements occur due to tectonic stress
  • Fractures are cracks without movement
  • Continued plate extension occurs at mid-ocean ridges, splitting and displacing new oceanic lithosphere
  • New lava solidifies, then is fractured
  • Fractures are planar
  • Cracks/fissures within a body of rock with no movement along planar surface

Seafloor Spreading Evidence

  • Observation and measurements of the seafloor
  • Dredging and drilling
  • Marine sediment thickness
  • Maps of earthquake distribution associated with mid-ocean ridges
  • Heat flow (highest over mid-ocean ridges and decreases away from ridges)
  • Submersibles and remote vehicles used for exploration of axial rifts

Continental Rifting

  • Ocean basins form when continents split
  • Upwelling asthenosphere beneath continents pushes overlying lithosphere, causing it to stretch and break along faults
  • Collapse of fault blocks creates rift valleys
  • As lithosphere stretches and thins, underlying asthenosphere rises more, melts, and creates magma/volcanoes

Continental Crust and Oceanic Crust

  • Oceanic crust is denser than continental crust, and therefore floats lower.
  • Continental crust floats like icebergs, thus continental-continental collisions don't involve subduction due to different density

Mountain Formation

  • Mountains frequently form in linear patterns from continent-continent collisions
  • Convergent plate boundaries are classified as continental-continental, continental-oceanic, and oceanic-oceanic.

Convergent Plate Boundaries

  • Continental-Continental: Collision zones, with no subduction, creating mountains like the Himalayas and European Alps. Thrust faulting occurs with thick rock layers detaching and moving slowly.
  • Continental-Oceanic: Oceanic plate subducts beneath the continental plate (e.g., Andes Mountains), creating volcanic chains.
  • Oceanic-Oceanic: One oceanic plate subducts beneath the other, creating volcanic island arcs.

Transform Plate Boundaries

  • Transform plate boundaries create earthquakes along faults, involving the displacement of massive rock blocks.
  • Planar weaknesses may appear between two fault blocks, but they are not related to tectonic plates.
  • Occurs along faults where massive rock blocks and surface features offset

Other Topics

  • Causes and types of earthquakes, including recurrence intervals, focus vs. epicenter, and displacement
  • Seismic waves: P waves, S waves, Love waves, Raleigh waves
  • Earthquakes and tectonic settings
  • Important events
  • Describing volcanic events, including the influence of silica on magma type

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Description

Explore the fascinating world of tectonic plates and their movements. This quiz covers key concepts like lithosphere, asthenosphere, and the characteristics of divergent plate boundaries. Test your knowledge of geological processes and features resulting from tectonic activities.

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