Plate Tectonics and Continental Drift
169 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What significant geological theory emerged in the 1960s that could explain various geologic processes?

  • Theory of relativity
  • Theory of plate tectonics
  • Theory of continental drift (correct)
  • Theory of geomorphology

    • Who is recognized for postulating the existence of a giant continent called Gondwana?

  • Abbé J.L. Giraud-Soulavie
  • Benjamin Franklin
  • Albert Einstein
  • Eduard Suess (correct)

    • In what centuries did European scientists begin to notice the jigsaw-puzzle fit of continents?

  • Eighteenth and nineteenth centuries
  • Seventeenth and eighteenth centuries
  • Fifteenth and sixteenth centuries
  • Sixteenth and seventeenth centuries (correct)

    • What did Benjamin Franklin speculate about the internal structure of the Earth in his letter?

    <p>The internal parts might be a fluid.</p> Signup and view all the answers

    Which major scientific revolution in geology allowed for a comprehensive explanation of tectonic processes?

    <p>Introduction of plate tectonics</p> Signup and view all the answers

    What term describes the processes involved in mountain building, volcanism, and earthquakes?

    <p>Tectonic processes</p> Signup and view all the answers

    Which concept was recognized as early evidence leading to the theory of plate tectonics?

    <p>The jigsaw puzzle fit of continents</p> Signup and view all the answers

    What was a key factor that distinguished the theory of plate tectonics from previous tectonic theories?

    <p>Ability to explain all geological processes</p> Signup and view all the answers

    What is the average duration of a magnetic chron?

    <p>500,000 years</p> Signup and view all the answers

    What phenomenon in rock layers indicates the direction of Earth's magnetic field at the time the rocks cooled?

    <p>Thermoremanent magnetization</p> Signup and view all the answers

    What do we call short-lived reversals within major magnetic chrons?

    <p>Magnetic subchrons</p> Signup and view all the answers

    How does the seafloor spreading hypothesis explain the banded patterns of magnetism on the ocean floor?

    <p>From cooling of lava that became magnetized</p> Signup and view all the answers

    When studying volcanic rocks, what percentage has been found to have a magnetization opposite to the current magnetic field?

    <p>50%</p> Signup and view all the answers

    What term describes the localized stronger field recorded above rocks magnetized in the normal direction?

    <p>Positive magnetic anomaly</p> Signup and view all the answers

    What is the average spreading rate for mid-ocean ridges around the world?

    <p>50 mm/year</p> Signup and view all the answers

    What is the main significance of the magnetic time scale constructed by geologists?

    <p>To date magnetic anomalies on the seafloor</p> Signup and view all the answers

    Which plates are mentioned as having a rapid spreading rate at the East Pacific Rise?

    <p>Pacific and Nazca plates</p> Signup and view all the answers

    Which scientist is NOT associated with the research on Earth's magnetic field?

    <p>Albert Einstein</p> Signup and view all the answers

    What physical principle allows scientists to calculate the speed of seafloor spreading?

    <p>Speed = distance/time</p> Signup and view all the answers

    What happens to the bands of magnetized rocks as they move away from the mid-ocean ridge?

    <p>They maintain their symmetry</p> Signup and view all the answers

    What is the maximum recorded speed for spreading in the East Pacific Rise?

    <p>150 mm/year</p> Signup and view all the answers

    What occurs at divergent boundaries?

    <p>Plates move apart and new lithosphere is created</p> Signup and view all the answers

    Which of the following did NOT contribute to the theory of plate tectonics?

    <p>Isaac Newton</p> Signup and view all the answers

    Where is new lithosphere primarily formed?

    <p>Along mid-ocean ridges</p> Signup and view all the answers

    What is the primary process that leads to the recycling of lithosphere?

    <p>Subduction at convergent boundaries</p> Signup and view all the answers

    Which plate is the largest tectonic plate?

    <p>Pacific Plate</p> Signup and view all the answers

    How do scientists characterize plate boundaries?

    <p>By the direction of movement of the plates</p> Signup and view all the answers

    What role do earthquakes play in understanding plate tectonics?

    <p>They signify tectonically active features like rifts</p> Signup and view all the answers

    What term describes the movement of rigid plates over Earth's surface?

    <p>Plate tectonics</p> Signup and view all the answers

    What happens at transform faults?

    <p>Plates slide horizontally past each other</p> Signup and view all the answers

    Which of the following is a small tectonic plate?

    <p>Caribbean Plate</p> Signup and view all the answers

    What hypothesis did Hess and Dietz propose regarding the Earth's crust?

    <p>The crust is constantly separating and forming new lithosphere</p> Signup and view all the answers

    Which geological feature is specifically associated with the Ring of Fire?

    <p>Intense volcanic and earthquake activity</p> Signup and view all the answers

    What major conclusion did scientists reach by 1970 regarding plate tectonics?

    <p>The evidence for plate tectonics had become widely accepted</p> Signup and view all the answers

    What primarily maintains the separation between the upper and lower systems in the hypothesis of stratified convection?

    <p>The upper system is composed of lighter rock.</p> Signup and view all the answers

    What evidence do scientists look for to support the hypothesis of whole-mantle convection?

    <p>Lithospheric graveyards below convergent boundaries.</p> Signup and view all the answers

    How far have some descending lithospheric slabs reportedly gone beneath the core-mantle boundary?

    <p>2890 km</p> Signup and view all the answers

    What force is primarily responsible for driving plate tectonics as indicated in the graphic?

    <p>The gravitational pull on the lithospheric slabs.</p> Signup and view all the answers

    What is the prevailing belief regarding the nature of rising convection currents under mid-ocean ridges?

    <p>They are slow and spread out over broad regions.</p> Signup and view all the answers

    What unique feature is associated with mantle plumes?

    <p>They create narrow jet-like upwellings.</p> Signup and view all the answers

    How does the recycling of lithosphere relate to the breakup of Pangaea?

    <p>Lithosphere equivalent to Earth's surface area has been recycled.</p> Signup and view all the answers

    What distinguishes whole-mantle convection from stratified convection?

    <p>Whole-mantle convection allows lithospheric recycling to lower depths.</p> Signup and view all the answers

    Which of the following describes the behavior of the lower mantle in terms of convection?

    <p>It convects sluggishly compared to the upper mantle.</p> Signup and view all the answers

    Why is seafloor spreading considered a passive process by many scientists?

    <p>It occurs wherever plates are pulled apart.</p> Signup and view all the answers

    What geological feature is characteristic of divergent boundaries?

    <p>Rift valleys</p> Signup and view all the answers

    Which of the following is an example of a rift that is further along in the spreading process?

    <p>Gulf of California</p> Signup and view all the answers

    What is the process called when one tectonic plate descends beneath another?

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

    What geological feature marks the deepest point on Earth’s ocean floor?

    <p>Marianas Trench</p> Signup and view all the answers

    Why does the continental lithosphere override the oceanic lithosphere during ocean-continent convergence?

    <p>It is less dense than oceanic lithosphere.</p> Signup and view all the answers

    Which geologic feature is created as a result of ocean-ocean convergence?

    <p>Island arcs</p> Signup and view all the answers

    What catastrophic event was linked with the eruption of Nevado del Ruiz in 1985?

    <p>A volcanic mudflow</p> Signup and view all the answers

    Which region is considered a failed rift that became inactive about 5 million years ago?

    <p>Gulf of Suez</p> Signup and view all the answers

    What is formed when magma rises and results in volcanic activity as mantle material melts?

    <p>Volcanic arc</p> Signup and view all the answers

    What kind of geologic activity can result from the convergence of the South American Plate and the Nazca Plate?

    <p>Earthquakes and volcanic activity</p> Signup and view all the answers

    What feature is typically associated with subduction zones?

    <p>Deep-sea trenches</p> Signup and view all the answers

    Which boundary type is known for producing some of the world's largest earthquakes?

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

    Where is the Cascade Range located in relation to a convergent boundary?

    <p>Above a subduction zone</p> Signup and view all the answers

    What type of geological processes occur at convergent boundaries?

    <p>Complex and variable</p> Signup and view all the answers

    What significant geological event marked the creation of all the current seafloor on Earth?

    <p>The breakup of Pangaea</p> Signup and view all the answers

    Which feature helps to identify ancient collisions of paleocontinents?

    <p>Old mountain belts</p> Signup and view all the answers

    How does the thermoremanent magnetization of continental fragments help scientists?

    <p>It reveals ancient orientations and magnetic latitudes</p> Signup and view all the answers

    What supercontinent formed approximately 1.1 billion years ago?

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

    What geological process contributes to the current isolation of Antarctica from warmer ocean waters?

    <p>The formation of the circumpolar seaway</p> Signup and view all the answers

    Which geological event occurred around 40 million years ago that affected the climate of Antarctica?

    <p>The breakup of Australia from Antarctica</p> Signup and view all the answers

    How have the movements of tectonic plates affected the planet's climate over millions of years?

    <p>They have influenced the formation of ice sheets</p> Signup and view all the answers

    What aspect of geology has been influenced by the discovery of paleocontinents?

    <p>Evolutionary biology perspectives</p> Signup and view all the answers

    What primary mechanism drives the movement of tectonic plates according to the theory discussed?

    <p>Mantle convection</p> Signup and view all the answers

    What geological formation resulted from the collision of India with Asia?

    <p>Tibetan Plateau</p> Signup and view all the answers

    What role does plate tectonics play in the understanding of rock formation?

    <p>It correlates rock formations globally</p> Signup and view all the answers

    What geological process has destroyed the seafloor created during earlier episodes of continental drift?

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

    What type of geological evidence is crucial for reconstructing the positions of ancient continents?

    <p>Rock types and magnetization</p> Signup and view all the answers

    Which of the following does not accurately represent a consequence of plate tectonics?

    <p>Stabilization of weather patterns</p> Signup and view all the answers

    What is the primary method used to determine the ages of seafloor regions?

    <p>Mapping magnetic anomalies</p> Signup and view all the answers

    What technique allows geologists to measure intercontinental distances with high accuracy?

    <p>Global Positioning System (GPS)</p> Signup and view all the answers

    What evidence validated the magnetic time scale and supported seafloor spreading?

    <p>Ages of samples from drill cores</p> Signup and view all the answers

    How did ancient Egyptian builders orient the Great Pyramid?

    <p>Based on the stars' positions</p> Signup and view all the answers

    What was a notable result of the seafloor drilling program launched in 1968?

    <p>Collection of core samples from seafloor rocks</p> Signup and view all the answers

    What phenomenon indicates that the crust is older at greater distances from mid-ocean ridges?

    <p>Ages of drill core samples</p> Signup and view all the answers

    What technology provides an outside frame of reference for geodesic measurements today?

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

    How are the depths of the seafloor determined using remote sensing?

    <p>Magnetic field measurements</p> Signup and view all the answers

    Why did plate movements become easier to measure starting in the late 1970s?

    <p>Development of new geodetic techniques</p> Signup and view all the answers

    What led to the Great Pyramid's misalignment with true north over centuries?

    <p>Drifting of the African tectonic plate</p> Signup and view all the answers

    How do geologists validate the ages of fossils found at the seafloor?

    <p>Correlating with the magnetic time scale</p> Signup and view all the answers

    What does the presence of organic material in seafloor sediments indicate?

    <p>Accumulation of ancient marine life after crust formation</p> Signup and view all the answers

    What role do quasars play in modern geodesy?

    <p>They serve as distant reference points for measurements.</p> Signup and view all the answers

    Which aspect of plate movement measurements is NOT highlighted as reliable over long periods?

    <p>Rate of erosion at plate boundaries</p> Signup and view all the answers

    What kind of geological feature is formed at subduction zones like those off the northeastern coast of Honshu, Japan?

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

    Which of the following best describes transform faults?

    <p>They involve horizontal sliding of tectonic plates.</p> Signup and view all the answers

    What is a characteristic outcome of continent-continent convergence, such as that between the Indian and Eurasian plates?

    <p>Development of mountain ranges</p> Signup and view all the answers

    Which example of a transform fault is found in California?

    <p>San Andreas Fault</p> Signup and view all the answers

    What phenomenon occurs due to the seafloor being affected by Earth's magnetic field changes?

    <p>Magnetic anomalies</p> Signup and view all the answers

    What significant geological event is associated with the collision of the Indian and Eurasian plates?

    <p>Mounting of the Himalayan range</p> Signup and view all the answers

    How does the lithosphere behave at transform fault boundaries?

    <p>It slips horizontally without alterations.</p> Signup and view all the answers

    What do scientists use to analyze past plate movements effectively?

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

    What occurs when rocks at transform fault boundaries have been sliding past each other for a long time?

    <p>Differences in the types and ages of the rocks</p> Signup and view all the answers

    What geological consequence can occur at transform faults?

    <p>Severe earthquakes</p> Signup and view all the answers

    What kind of convergence occurs when two continents collide?

    <p>Continent-continent convergence</p> Signup and view all the answers

    What does thermoremanent magnetization enable geologists to study?

    <p>Earth's magnetic field changes</p> Signup and view all the answers

    Which of the following plates is NOT mentioned as having a transform fault boundary?

    <p>African Plate</p> Signup and view all the answers

    What type of geological formation is associated with historical continent-continent collisions?

    <p>Mountain ranges</p> Signup and view all the answers

    What event led to the assembly of the supercontinent Pangaea?

    <p>Continental drift</p> Signup and view all the answers

    Which of the following statements about seafloor isochrons is true?

    <p>The spacing of isochrons indicates the rate of seafloor spreading.</p> Signup and view all the answers

    How long ago did North America begin to rift away from Europe?

    <p>200 million years ago</p> Signup and view all the answers

    What do transform-fault boundaries primarily allow for?

    <p>Plate sliding past each other</p> Signup and view all the answers

    Which feature of the Earth's plates is illustrated by the distances between points on the same plate?

    <p>Rigidity of the plates</p> Signup and view all the answers

    What geographical feature indicates faster spreading rates in the ocean?

    <p>Widely spaced isochrons</p> Signup and view all the answers

    What geological process produces the youngest oceanic rocks?

    <p>Seafloor spreading</p> Signup and view all the answers

    What major event occurred about 240 million years ago concerning Pangaea?

    <p>Formation of the supercontinent</p> Signup and view all the answers

    What is the approximate age of the oldest known oceanic rocks found in the western Pacific?

    <p>200 million years</p> Signup and view all the answers

    What did the breakup of Gondwana primarily separate?

    <p>South America, Africa, India, and Antarctica</p> Signup and view all the answers

    How do geologists utilize isochrons to understand previous plate positions?

    <p>By correlating adjacent isochrons across a ridge</p> Signup and view all the answers

    After the breakup of Pangaea, which continents formed Laurasia?

    <p>North America and Europe</p> Signup and view all the answers

    In what manner does the oceanic lithosphere primarily change over time?

    <p>It forms, cools, and is recycled into the mantle.</p> Signup and view all the answers

    Which event is used to reconstruct the history of plate movements across Earth?

    <p>Analyzing the distances between points on rigid plates</p> Signup and view all the answers

    What significant change occurs in positions of continents as tectonic plates move?

    <p>Distances between points on rigid plates vary greatly.</p> Signup and view all the answers

    What name did Alfred Wegener give to the proposed supercontinent that broke up into the continents we know today?

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

    What major flaw did Wegener's hypothesis about continental drift have according to his contemporaries?

    <p>Lack of a driving mechanism</p> Signup and view all the answers

    Which fossil was notably found in both Africa and South America, supporting the idea of continental drift?

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

    What was identified as the significant driving force for continental drift after World War II?

    <p>Convection currents in the mantle</p> Signup and view all the answers

    Which feature of the seafloor contributed to evidence for Wegener's theory of continental drift?

    <p>Mid-Atlantic Ridge</p> Signup and view all the answers

    Who were the geologists that mapped the undersea mountain chain known as the Mid-Atlantic Ridge?

    <p>Bruce Heezen and Marie Tharp</p> Signup and view all the answers

    What type of ancient rock assemblages did Wegener point to as evidence for continental drift?

    <p>Matching crystalline rocks</p> Signup and view all the answers

    Why were fossils of Mesosaurus significant in the context of continental drift?

    <p>They indicated the continents were connected in the past.</p> Signup and view all the answers

    Which hypothesis did Arthur Holmes propose in 1928 regarding continental movement?

    <p>Convection currents in the mantle push continents apart.</p> Signup and view all the answers

    What type of geological feature was discovered along the Mid-Atlantic Ridge?

    <p>A deep rift valley</p> Signup and view all the answers

    What did the mapping of the Atlantic seafloor reveal regarding its composition?

    <p>It was made of relatively young basalt.</p> Signup and view all the answers

    What conclusion did scientists draw from glacial deposits found across several continents?

    <p>All continents were once part of a single landmass.</p> Signup and view all the answers

    How did some scientists initially react to the idea of continental drift proposed by Wegener?

    <p>They doubted its validity due to rigid crust assumptions.</p> Signup and view all the answers

    What occurs at divergent boundaries in ocean basins?

    <p>New oceanic lithosphere is created</p> Signup and view all the answers

    What is a characteristic feature formed at ocean-ocean convergent boundaries?

    <p>Deep-sea trenches</p> Signup and view all the answers

    How does continental crust differ from oceanic crust?

    <p>It is lighter and weaker</p> Signup and view all the answers

    What type of boundary is characterized by plates sliding horizontally past each other?

    <p>Transform-fault boundary</p> Signup and view all the answers

    What geological feature is associated with continental rift zones?

    <p>Parallel rift valleys</p> Signup and view all the answers

    Which phenomenon is primarily caused by mantle convection at oceanic spreading centers?

    <p>Creation of new oceanic crust</p> Signup and view all the answers

    What happens to oceanic lithosphere when it meets continental lithosphere at convergent boundaries?

    <p>It is recycled back into the mantle</p> Signup and view all the answers

    What can be created as a result of continent-continent convergence?

    <p>High mountains and plateaus</p> Signup and view all the answers

    How does the recycling of oceanic lithosphere differ from that of continental lithosphere?

    <p>Oceanic lithosphere is more easily recycled</p> Signup and view all the answers

    Which plate boundary type is often associated with volcanic activity due to subduction?

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

    Which of the following is a feature typical of transform-fault boundaries?

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

    What type of feature forms at mid-ocean ridges as a result of rifting?

    <p>New oceanic lithosphere</p> Signup and view all the answers

    What is a key characteristic of transform faults?

    <p>They exhibit lateral movement</p> Signup and view all the answers

    What does subduction at a convergent boundary often lead to?

    <p>Creation of deep-sea trenches</p> Signup and view all the answers

    Which process is primarily responsible for the movement of tectonic plates?

    <p>Gravitational pull of subducting slabs</p> Signup and view all the answers

    What is the role of seafloor spreading in the theory of plate tectonics?

    <p>It is the passive upwelling of mantle material</p> Signup and view all the answers

    What was one evidence against the theory that plates are passively dragged by mantle convection?

    <p>The lack of significant attachments of descending slabs for slower-moving plates</p> Signup and view all the answers

    Which supercontinent was formed approximately 1.1 billion years ago?

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

    What occurred as a result of the breakup of Pangaea?

    <p>Opening of rifts that released lava</p> Signup and view all the answers

    How did the Nazca Plate's movement affect the South American Plate?

    <p>It sucked the South American Plate toward the Pacific</p> Signup and view all the answers

    What geological feature was primarily associated with the superocean Panthalassa?

    <p>The ancestral Pacific Ocean</p> Signup and view all the answers

    Why are the plates considered to 'fall back' into the mantle?

    <p>Due to their own weight and density</p> Signup and view all the answers

    Which of the following plates is identified as a faster-moving plate?

    <p>Australian Plate</p> Signup and view all the answers

    What is one of the main driving forces behind the movement of tectonic plates?

    <p>Gravity acting on the cold lithosphere</p> Signup and view all the answers

    What are the consequences of the gravitational pull exerted by subducting slabs?

    <p>Movement of plates downward into the mantle</p> Signup and view all the answers

    Which plate is currently believed to have a small impact on the Atlantic Ocean's formation?

    <p>Nazca Plate</p> Signup and view all the answers

    Which event signaled the initial breakup of Pangaea?

    <p>Opening of rifts and volcanic activity</p> Signup and view all the answers

    What geological event marked the early stages of the breakup of Pangaea?

    <p>The partial opening of the Atlantic Ocean</p> Signup and view all the answers

    Which ocean began to close as India moved northward toward Asia?

    <p>Tethys Ocean</p> Signup and view all the answers

    Which continents began to split away from Africa approximately 150 million years ago?

    <p>India, Antarctica, and Australia</p> Signup and view all the answers

    What is the primary driving force of plate tectonics?

    <p>Mantle convection</p> Signup and view all the answers

    What event contributed to the breakup of Pangaea by raising it slightly?

    <p>Formation of hot bulges in the mantle</p> Signup and view all the answers

    What geological feature forms as plates slide downhill off the crest of the Mid-Atlantic Ridge?

    <p>Seafloor spreading zones</p> Signup and view all the answers

    How deep can the recycling process of lithospheric material extend within the mantle?

    <p>2890 km</p> Signup and view all the answers

    What factor is thought to govern the rates of plate movement?

    <p>Forces related to sinking slabs and elevated ridges</p> Signup and view all the answers

    Which two geological systems do some scientists believe the mantle might be divided into?

    <p>Upper and lower mantle</p> Signup and view all the answers

    What resulted from the tectonic activity after the formation of Pangaea?

    <p>The establishment of the modern continents and oceans</p> Signup and view all the answers

    What type of geological forces provide evidence of the compression of plates?

    <p>Gravitational forces from ridges</p> Signup and view all the answers

    Which ocean's opening and widening occurred by 66 million years ago?

    <p>Atlantic Ocean</p> Signup and view all the answers

    What is the significance of the core-mantle boundary in terms of material exchange?

    <p>It prevents significant exchange of materials between the two layers.</p> Signup and view all the answers

    What major geological feature was raised during the formation of Pangaea?

    <p>The Mid-Atlantic Ridge</p> Signup and view all the answers

    Study Notes

    Plate Tectonics Revolution

    • Geologists spent nearly 200 years developing theories about tectonics (mountain building, volcanism, earthquakes).
    • The theory of plate tectonics unified these processes. This was a similar scientific revolution to physics' development of relativity and biology's understanding of DNA.
    • Plate tectonics was synthesized about 50 years ago, though the foundation of the theory, continental drift, was recognized earlier in the 20th century.

    Continental Drift

    • The idea of continental drift (large-scale continent movement) has a long history dating back to the late 16th and 17th centuries.
    • European scientists recognized the puzzle-like fit of coastlines on opposite sides of the Atlantic.
    • Eduard Suess (Austrian geologist) furthered the idea that current southern continents were once a single landmass (Gondwana).
    • Alfred Wegener (German meteorologist post-WWI) wrote a book ("Origin of Continents and Oceans") detailing similarities in geologic features and fossils on opposite sides of the Atlantic. He proposed Pangaea (all lands).
    • Wegener's hypotheses about speed and forces were incorrect, lowering his credibility among geologists initially.
    • The geologic evidence for drift included: similar rock ages, structures, fossils (like Mesosaurus fossils found in both South America and Africa), and glacial deposits across continents (suggesting a single ice age).

    Seafloor Spreading

    • Skeptics questioned the physical possibility of continental drift due to a lack of a plausible driving force. Wegener’s idea of continents floating on oceanic crust wasn't valid.
    • Arthur Holmes proposed convection currents in Earth's mantle as the driving force.
    • Maurice Ewing and colleagues (Bruce Heezen, Marie Tharp) explored the sea floor using advanced technology, revealing young basalt, not old granite. They also discovered the Mid-Atlantic Ridge with a deep rift. Their work confirmed plate spreading.
    • Harry Hess and Robert Dietz proposed the seafloor spreading hypothesis: new crust forming at mid-ocean ridges, spreading away from the ridges. This process could explain how continents could move apart.

    The Great Synthesis (1963-1968)

    • The seafloor spreading hypothesis explained movement, but created the question of whether the seafloor was being destroyed.
    • Some believed Earth was expanding.
    • Other geologists understood seafloors were recycled through the mantle (especially in the Ring of Fire).
    • J. Tuzo Wilson described global tectonics in regards to rigid plates moving on Earth’s surface. He characterized different types of plate boundaries.
    • By 1970, plate tectonics became widely adopted within geology.

    Plates and Their Boundaries

    • The lithosphere is comprised of a mosaic of rigid plates moving on the asthenosphere.
    • The theory identifies three fundamental types of plate boundaries:
      • Divergent: Plates move apart, creating new lithosphere.
      • Convergent: Plates move together, with one plate subducting under the other, causing recycling and trenches. There are oceanic-oceanic and oceanic-continental types, as well as continental-continental types which build mountain ranges.
      • Transform: Plates slide horizontally past each other.
    • Plate boundaries can be a combination of these types.
    • Continental crust behavior, lighter and weaker than oceanic crust, complicates continental boundaries.

    Rates and History of Plate Movements

    • Scientists use methods like analyzing seafloor magnetic anomalies (revealing magnetic reversals within rock layers) and deep-sea drilling to understand plate movement rates.
    • Magnetic anomalies on the sea floor act like a magnetic tape recorder that shows periods of normal and reversed magnetism, correlating with ages of rocks.
    • Rates are determined by combining spreading rates and directions at divergent boundaries.
    • Deep-sea drilling records sediment ages that match predicted seafloor ages from magnetic patterns.
    • Geodesy, including GPS, measures plate movement rates directly.

    The Grand Reconstruction

    • Pangaea was a supercontinent 250 million years ago.
    • Scientists reconstructed Earth's past plate movements through seafloor isochrons (equal-age boundaries) allowing reconstruction of earlier continents (like Rodinia).
    • Mountain belts and fossils confirm these ancient movements.
    • Magnetic measurements offer additional clues to reconstructions and paleocontinents.
    • Understanding the past helps us predict future plate movements and continental configurations.

    Mantle Convection: The Engine of Plate Tectonics

    • Mantle convection (rising and sinking of hot and cold mantle material) drives plate movement.
    • The force of sinking slabs (especially oceanic slabs subducting) drives plates toward convergent boundaries. This is considered a major driving force compared to purely "dragged" plate movements.
    • The forces governing plate movement are still being studied with models.
    • Different hypotheses regarding the recycling process depth exist: whole-mantle convection versus stratified convection.
    • There are regional exceptions of concentrated upwelling called mantle plumes. This differs from the general spreading pattern of rising, more spread-out convection currents.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz explores the pivotal concepts of plate tectonics and continental drift. Discover how these theories revolutionized our understanding of geological processes like mountain building, volcanism, and earthquakes. Learn about key figures like Alfred Wegener and the historical development of these ideas over the centuries.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser