Geology Lecture Outline

Plate Tectonics – (Chapters 2, 13, 14)

 

I. Lecture Content

Introduction – Earth's Ever-Changing Surface - How so?

Early Ideas - Pondering Earth's Continental Jigsaw Puzzle

Wegener and the Continental Drift Hypothesis - Eye-Opener

Evidence for Continental Drift - Many Continent "Connections"

Geology of the Seafloor – Nothing Like the Continents

Major Discoveries about the Seafloor - Let the Spreading Begin

Seafloor Spreading and Subduction - Creation and Destruction

Theory of Plate Tectonics - Unifying, Earth-Shaking Paradigm

Plates and Plate Boundaries - Inter-Plate Relationships

Determining Plate Movement & Motion - Past, Present & Future

Driving Forces of Plate Tectonics - Where's the Big Ponies?

Pangea and The Wilson Cycle - 500 Ma Supercontinent cycles

Paleogeographic Reconstruction - Modeling Earth's Past

Plate Tectonics and Natural Resources - Rhyme and Reason

 

II. Introduction

A. How and Why Does the Earth Continue Changing?

              1. Earth's surface has never stopped changing since it first

       formed nearly 4.6 billion years ago.

 

              2. There must be very energetic, long-lived forces within

                      the Earth to maintain the global-scale earthquake,

volcanic, and mountain-building activities we observe.

 

              3. Earth scientists have been studying the Earth for several

                      100 years in hopes of answering this question.

 

              4. Numerous ideas or theories have been proposed to

 explain Earth's long and eventful geologic history,

 and its amazing variety of features and phenomena.

 

              5. The unifying Theory of Plate Tectonics is, by far, the best

                      and most accepted theory for explaining all of Earth's

 geologic and some biological phenomena.

 

       B. Ever-Mounting Evidence Supports Plate Tectonics

              1) Seafloor and Continent Anatomy

              2) Seismic Data

              3) Fossil Record

              4) Rock Dates

              5) Magnetic Patterns

              6) Satellite Geodesy

              7) Volcanic Chemistry

              8) Exotic Terranes

 

III. Early Ideas About Continents Drift

A.  Concept of "Drift" First Derived From Continent Fit

1. Fit of Africa and South America gave several people the

     idea that they were once a single landmass and that

      they eventually "drifted" apart.

·      Leonardo de Vinci - 1500's

·      Francis Bacon - 1620

·      Edward Suess - 1885

·      Alfred Wegener - 1912

 

       B. Alfred Wegener and His Continental Drift Theory

              1. German meteorologist and polar explorer

 

              2. Credited with the Theory of Continental Drift (1912)

 

              3. Outline of Continental Drift Theory

·      All of Earth's landmasses had once been joined into a

                      single supercontinent (named Pangaea) surrounded by

                      a single superocean (named Panthalassa).

 

·      Pangea broke into smaller pieces (today's continents)

                         around 200 Ma.  (Ma = million years ago)

 

·      After the breakup of Pangea, the pieces (continents)

                       started moving away from one another; have been

                       moving ever since; and are still moving.

                            

              4. Wegener amassed numerous lines of evidence from all

                     corners of the world to support his 'outrageous' theory   

·      Geological data:

ü    Continental margin fits

ü    Match-up of truncated mountain ranges and faults

ü    Match-up of stratigraphic sequences and mineral

       deposits

 

·      Paleontological data:

ü    Match-up of extinct plant species fossil localities

ü    Match-up of extinct animal species fossil localities

 

·      Climatology data:

ü    Match-up of temporally-equivalent glacial deposits

ü    Discovery of coal deposits in Antarctica

 

 

            5. Wegener proposed a mechanism for continental drift.

·      Heavy continents were slung toward the equator by

   centrifugal forces generated by the spinning Earth.

 

·      The slinging force coupled with tidal drag created by

  Sun's and Moon's gravity caused continents to drift.

 

            6. Wegener had many harsh critics who cut him down over

                  both the (unselected) evidence, and his drift mechanism.

 

·       How do continents move through solid ocean crust?

 

·       If so, then where is the "wake" left behind on seafloor?

 

·       Drift mechanism deemed geophysically impossible.

ü    Ideas about the mantle were different than today

 

·       No known power source to cause drift.

 

            7. Wegener's Continental Drift Theory nearly dies with him

 

   C.  Post-Wagener Research Keeps the "Drift" Idea Alive

 

            1. Several scientists transform the "drift" idea with new

                   research on Pacific volcanism and earthquake.

 

·       Kiyoo Wadati - 1935 - Connected EQ's with "drift"

 

·       Hugo Benioff - 1940 - Mapped "Pacific Ring of Fire"

 

           2. Radiometric age-dating of world's seafloors reveal that the

                oldest rocks and overlying sediments < 200 Ma.

 

·       Why was oceanic crust so young?

 

           3. Oceanographers in the Atlantic map the Mid-Atlantic Ridge

 

·       The Mid-Atlantic Ridge mimics the continent outlines

 

·       Seafloor sediments thin at ridge; thickens landward

 

           4. Oceanographer maps flat-topped seamounts (guyouts)

 

            5. Mantle studies reveal a partially-melted layer in the upper

                   mantle, termed the asthenosphere.

 

           6.  Upper mantle shown to act like a very viscous plastic

·      The idea of crust isostically "floating" in mantle

 

            7. Paleomagnetic studies of numerous lava flows of all ages

                    from each of the continents revealed "wandering" of the

                   Earth's magnetic pole (mapped polar wander paths).

 

·      Each continent has a unique "wander path".

 

Ø    Question: Can magnetic poles wander from

                       the equator to the geographic pole?

 

·      For a given geologic age, there appears to be

                               two or more North magnetic poles.

 

Ø    Question: Can there be more than one North

               magnetic pole at any one given time?

                                            

IV. Overview of Earth’s Seafloor

 

A. Earth has Two Distinctive Topographic Regions

·       Continental Highlands - Continents

·       Oceanic Lowlands - Ocean basins

               

       B. The Earth's Seafloors are Rugged in Appearance and

            Have Considerable Topographic Relief.

·      See Figures

·       Much more topographic relief than the continents  

·       Seafloors have distinctive topographic features

·      Seafloors look much different than dry continents  

 

C. Earth's Seafloor is Divided into Two Major Provinces

1. Continental Margins

·       Submerged shallow platforms

·       Floored mostly by granitic rock

·       Varies greatly width, depth, and topographic relief

·       Vast majority of marine life concentrated there

 

2. Deep-Ocean Basins

·       Starts at base of continental margins

 

·       Deep seafloor consists primarily of:

       1.  High-standing mid-ocean ridge systems and

 

      2.  Low-standing sediment-covered abyssal plains

 

                3.  The two-province division is based upon the major

                       inherent differences between continental and oceanic

                       crust.

·      Composition (density)

·      Thickness

·      Isostatic equilibrium

 

V. Continental Margins - Shallow Marine

       A. Shallow Seafloor Rims of Ocean Basins

      1. Continental margins - the submerged edges of continents

 

  2. Continental margins are underlain by faulted blocks of

         granitic crust , overlying sediment piles, and possible

         accreted subduction zone material

 

B. Continental Margins are Classified into Two Types

      

      1. Passive Margins = Atlantic Ocean style

 

§      Situated within a plate

 

§      Develops after continental rifting and opening of a new

     ocean basin opening

 

§      Typically broad (avg. 100's km) with a very thick pile of

         accumulating sediments

 

§      Lacks much seismic or volcanic activity

 

      2. Active Margins = Pacific Ocean style

 

·      Situated at the leading edge of a continental plate

 

·      Develops after initiation of subduction

 

·      Typically narrow with rugged topography

 

·      Outer edge typically forms inner wall of ocean trench

 

·      Regionally unstable with much seismicity & volcanism

 

     3. See Figures

 

C. Physiological Features of a Continental Margin

                 

·      Continental Shelf

 

·      Continental Slope

 

·      Submarine Canyons

 

·      Continental Rise

D. The Continental Shelf   (See Figs

 

·      Shallow, submerged edge of continent between the

                   shoreline and continental slope (shelf-slope break)

 

·      Has a very low sloping angle (<< 1degree)

 

·      Typically shallow water depths (avg. = 75 m = 250 ft)

 

·      Greatly influenced by fluctuations in sea level

 

·      Shelf sediments are mainly influenced by waves and

        tidal currents

 

·      Site of abundant mineral resources and sea life

 

E. Continental Slope and Rise  (See Figs

 

·      Deeper, steeper, outermost edge of continent between the

    continental shelf and the deep ocean floor

 

·      A continental rise may separate the continental slope

            from the deep ocean basin along passive margins

 

ü     A continental rise forms a thick pile of sediments

                                  that have accumulated at the base of the

     continental slope

 

·      The shelf-slope break marks the abrupt transition between

      the slope and the shelf

 

·      Location of Earth's greatest depository of sediments

ü    Roughly 70% of Earth's sediments

 

·      Slope and Rise sediments are mainly influenced by

       gravity, and are transported down-slope via strong

       turbidity currents and deposit as submarine fans.

 

·      Submarine canyons and fan deposits are present on all

      continental slopes and rises, and on some continental

                        shelves

 

·      Submarine fan deposits grade into deep-ocean deposits

 

VI. Deep-Ocean Basins - True Oceanic Seafloor

A.  Ocean Basins are Classified by Size and Extent

 

·       Oceans - broad, large, and globally extensive

Examples: Pacific, Atlantic and Indian

 

·       Seas - narrow, smaller, and regionally limited

Example: Mediterranean, South China, & Red

 

B. Deep-ocean basins are underlain by basaltic crust

       1. Ocean Crust - A typical cross section (See Figs.

                                        

 

·      Layered basaltic crust covered by sediments

 

·      Rugged volcanic surface covered by layers upon

        layers of very fine pelagic sediment

 

ü    Pelagic clays

 

ü    Silica and carbonates Oozes

 

·      Oceanic igneous crustal column is also layered

 

Ø    Pillow lava basalt

 

Ø    Sheeted gabbroic dikes

 

Ø    Massive gabbro (intrusions)

 

Ø    Layered gabbro (intrusions)

 

Ø    Layered Peridotite

 

·      Oceanic crustal sections found on land are

        termed an ophiolite suite

 

C. Ocean Basins are Relatively Young Earth Features

·       Oldest part of ocean basins is 180 million years old

 

·       Average age of deep ocean seafloor is 60 million y.o.

 

·       Age distribution pattern of deep-ocean crust is striking

 

·       See Figure   - Ocean crust age map

       D. Deep-ocean basins are rugged with variable relief, and

          have a wide variety of distinctive physiological features

Ø    See Figure  - Seafloor Topographic Map

 

                 1. Mid-ocean ridges

 

                  2. Mid-ocean ridge fractures

 

                 3. Hydrothermal vents

 

                 4. Abyssal plains and Abyssal hills

 

5. Seamounts and Guyouts

 

6. Oceanic island chains

 

7. Oceanic plateaus

 

8. Trenches and Island arcs

 

E. Most Deep Ocean Features are the Result of Seafloor

             Spreading Processes Occurring at Mid Ocean Ridges

      

1. Seafloor spreading processes create:

      

ü    Mid-ocean rift valleys and ridge flanks

ü    Vast expanses of ocean crust (abyssal plains)

ü    Chains of volcanoes (seamounts and islands)

ü    Transform fracture systems

ü    Hydrothermal systems (black smokers)

 

2. See Figures

 

VII. Modern Revelations about the Seafloor

        A. Navy Oceanographer Proposes Seafloor Spreading

 

              1. Harry Hess formally proposes the theory of seafloor

                      spreading in 1962 to explain movement of continents.

 

              2. Hess's theory of seafloor spreading in a "nutshell".

·      Ocean and continental crust move together over

                           convecting cells of viscous upper mantle material

 

·      New ocean crust is created at mid-ocean ridges by

     upwelling mantle from the mantle.

 

·      Newly formed crust is then split apart by divergent

       forces and rafted laterally off the ridge and down the

       flanks of the ocean ridge, and eventually

 

                      3. Evidence sited: guyouts, seafloor topography,

                    crustal age profiles, and mantle characteristics.

 

             - Further Support of Seafloor Spreading Theory -

       B. Scripps Oceanographers Discover Magnetic Stripes

              1. Paleomagnetic polarity-reversal stripe patterns, termed

                      magnetic anomalies, are discovered on Pacific seafloor.

 

               2. Group of scientists from East Coast schools propose a

                      model to explain the magnetic anomaly stripes (1963)

o     Vine and Mathews - Cambridge

o     L. W. Morley - Canada

o     See Figure

·       Magma intruded at the crest of the ocean ridge records

       the polarity at the time it cooled

·       Newly formed crust splits and moves away to make room

     for new magma

·       Over time the repeated intrusion events would form a

      symmetrical set of magnetic stripes

 

              4. Similar magnetic anomalies found across the mid-ocean

               ridge off of Iceland and other ocean ridges world-wide.

 

       5. Paleomagnetic data-generated age profile of seafloors

             confirmed Vine, Mathews and Morley's proposal, and

              greatly support Hess's theory of seafloor spreading.

·      See Figure

      

      C. Deep-sea Drilling Projects Confirm Seafloor Spreading

               1. Analysis of ocean crust seafloor core samples

·      Sediments and Basalts = ophiolite sequence

·      See Fig.

 

               2. Seismic profiles of seafloors (oceanic crust x-sections)

 

     D. Researchers Discover that Crust Plunges into Mantle

                 1. Close correspondence between ocean trenches, active

                        island arcs, and earthquake-packed Benioff zones

 

                 2. Seismic profiles of trench-arc complexes

 

                 3. The term subduction is used to describe the process.

 

VIII. Origin of Islands, Atolls, Guyouts and Reefs

A. Islands and Seamounts are formed by volcanism

 

       1. Formed on or near mid-ocean ridges

 

       2. Basaltic shield volcanoes

 

       3. Migrate away from mid-ocean ridges over time

 

B. Atolls and Guyouts are Modified Oceanic Islands

 

       1. Circular coral reef systems develop around islands.

 

2. Oceanic crust cools and subsides with increasing age,

       causing the attached islands to also subside over time.

 

3. Islands slowly wear down to sea level by wave erosion.

 

       4. Upwards reef growth keep ups with sinking island.

 

       5. Island eventually worn down to below sea level, with

               only the growing reef able to maintain at sea level.

ü                     This stage of an island is termed an atoll.

 

6.  Eventually reef growth lags behind rate of atoll

       subsidence, and entire atoll structure becomes

                        permanently submerged - this is termed a guyout.

 

IX. The Unifying Theory of Plate Tectonics - A Paradigm

    A. Theory of Plate Tectonics Proposed (1965)

               1.  Conceptualized by geophysicist  J.T. Wilson

·       Also proposed the "Wilson Cycle"

·       Pangea and the 500 My Supercontinent cycle

 

               2. Combined ideas of continental drift, seafloor spreading,

                 subduction, and mantle convection into a single concept.

 

               3. The theory of plate tectonics is termed a unifying theory

                         because it is able to explain a great many geological

                      (and some biological) phenomenon.

 

     B. The Basic Components of the Plate Tectonics Theory

 

               1. The Earth's rigid outer layer is broken up into a dozen

                         or so separate lithospheric plates (see Fig. 12.14)

·      Lithosphere = crust + uppermost mantle

·      Large plates = continental and oceanic crust

 

2. The lithospheric plates are floating on the hot and

                       plastically mobile athenosphere

 

3. Heat convection cells in the athenosphere causes it to

      expand & rise up beneath the lithospheric plates

 

4. The rising athenosphere laterally diverges beneath the

                      lithosphere, causing a tensional drag effect at the base

                      of the lithosphere plate.

 

               5. The athenosphere drags the lithospheric plate with it

                      laterally until it turns downward with the descending

                        portion of the mantle thermal convection cell.

 

               6. The lithosphere plates jostle with each other as they

                       move independently about under the influence of the

                       underlying athenosphere.

              

               7. Three types of plate interactions = 3 types of boundaries

·      Divergent boundaries

·      Convergent boundaries

·      Transform boundaries

 

X. Three Types of Plate Boundaries (See Table

 

        A.  Divergent Plate Boundaries - Two Styles

 

Ø    A line along which two plates move apart

 

Ø    Tensional tectonic forces dominate

 

Ø    Oceanic crust forms along divergent boundaries

 

Ø    See Figures

                     

                      1. Continental (rifting)

·       Spreading center

 

ü    Rift valley (pull-apart basin)

 

·       Examples: East Africa Rift Valley

 

                      2. Oceanic (basin extension)

·       Spreading center

 

ü    Mid-ocean ridge system

ü    Transform fracture system

 

·       Examples: Mid Atlantic Ridge

 

        B.  Convergent Plate Boundaries - Three Styles

 

Ø    A line along which two plates move towards each other

 

Ø    Compressional tectonic forces usually dominate

 

Ø    Ocean crust is consumed at convergent boundaries

 

Ø    See Figures

 

                      1. Oceanic-Oceanic Plate Convergence

·       Subduction zone complex

 

ü    Oceanic trench

ü    Volcanic island arc

 

·       Examples: Aleutian Island trench/arc belt

 

                    2. Oceanic-Continental Plate Convergence

·       Subduction zone complex

ü    Oceanic trench

ü    Volcanic continental margin arc

 

·       Examples: Andes trench/arc belt

 

                   3. Continental-Continental Plate Convergence

·       Continental collision complex

ü    Uplifted fold/thrust mountain belt

ü    Collapsed ocean basin suture zone

 

·       Examples: Himalayas

 

         C.  Transform Plate Boundaries - Three Styles

Ø    Line along which two plates slide laterally past the other

 

Ø    Shearing tectonic forces usually dominate

 

Ø    Crust is neither created of destroyed at this boundary

 

Ø    See Figures

 

                      1. Oceanic-Oceanic Plate Transform

·      Transform fault

ü    Ridge-ridge fracture zone

ü    Ridge-trench fracture zone

ü    Trench-trench fracture zone

·       Examples: Mendocino fracture zone

 

                      2. Oceanic-Continental Plate Transform

·      Transform fault

ü    Great strike-slip fault zone

 

·       Examples: Queen Charlotte Fault

 

                      3. Continental-Continental Plate Transform

·      Transform fault

ü    Great strike-slip fault zone

 

·       Examples: San Andreas Fault

 

XI. Determining Plate Motion - Past, Present and Future 

      A.  Several Aspects of Determining Tectonic Plate Motion

                           1. Determine present rate (speed) of motion of each plate

 

             2. Determine present direction of motion for each plate

·       Relative motion - in relation to other plates

·       Absolute motion - in relation to fixed point in mantle

 

            3. Determine past rates and directions of motion of each plate

 

            4. Reconstruct ancient plate configurations for various past

                     time periods

 

            5. Predict future plate configurations

 

      B. Methods Used for Determining Plate Motions

 

           1.  Magnetic Anomaly Dating of the seafloor crust

·         Distance from the ridge axis to the any specific magnetic

   anomaly indicates the width of new oceanic seafloor crust

   that formed since the magnetic anomaly was recorded

   (a time interval)

 

·       For a given interval of time, the wider the (magnetic

    anomaly) strip of seafloor, the faster the plate moved.

 

·       Both present average rate of movement and relative

                       direction of motion can be determined with this method

 

·       Both past average rates of movement and relative

       directions of motion can also be calculated with this

       method for various past time periods.

 

·       Past rates are calculated by dividing the distance

        between anomalies by the amount of time that has

        elapsed between the anomalies

 

·       Past plate positions can also be calculated, because

        magnetic anomalies are parallel and symmetrical with

        respect to the ocean spreading ridge

 

ü    Determine continent position by move the

                anomaly stripes back to the spreading ridge

 

       2. Laser-Satellite Ranging Technique

·       Shooting a laser beam pulse from one tectonic plate to

      another by bouncing it off a geo-stationary satellite

 

·       As the plates move relative to one another, the sending

      and receiving laser stations will also move

 

·       The rate of movement and direction of relative motion of

       the two plates can be calculated from differences in the

      recorded elapsed times of the laser pulses taken over a

      given period of time

 

·       Only useful for present plate motion rates and direction

 

·       The results of this method correlate with those made with

       the magnetic anomaly dating method

 

       3. Quasar Radio Signal Ranging Technique

·       Virtually identical to the above laser-satellite method, except

     in a sort of reverse fashion

 

·       Only difference is that the time-elapsed signal is not ground

      based, rather its from fixed object in space

              

      4. The Hot Spot Technique

·       Only method that may provide absolute rates of movement

      and direction of motion of plates

 

·       Absolute determinations possible because active hot spots

     mark the sites of fixed mantle plumes that appear to originate

                        from deep within the mantle

 

·        Hot spots are independent of lithospheric plates and fixed

       with respect to Earth's rotational axis

 

·   Useful as reference points for determining paleolatitude

 

XII. Causes of Plate Motion - Plate Driving Mechanisms

     A. Presently there are three proposed mechanisms for

             driving the movement of the tectonic plates

 

Ø    Mantle Convection

 

Ø    Ridge Push

 

Ø    Slab Pull

 

                1.  Friction of mantle (athenosphere) convection

                     currents against bottom of plates

 

·       Plates dragged by coupled traction forces

 

·       Like a raft carried by a river current

 

·       Termed "plate drag"

 

·       See Figure

 

                2. Lateral outward push of new, high-standing mid- 

                    ocean ridge lithosphere

 

·       Plate slides off raised ridge, due to force of gravity;

     raised end exerts a pushing effect on low end

 

·       Like a sliding cookies off a tipped baking sheet

 

·       Termed "ridge push"

 

·       See Figure

                      

                3. Downward pull of a descending plate's cold,

                    dense leading edge.

 

·       Extra-dense plate edge isostatically sinks down into

  the mantle under its own weight; the rest (of the plate)

                        gets pulled along with it.

 

·       Like a table cloth slipping off the end of a table

 

·       Termed "slab pull"

 

·       See Figure

 

xIII. Birth, Growth and Death of an Ocean Basin

      ---- The Wilson Cycle ---- 

 

      A.  Initiation of New Ocean Basin via Continental Rifting

   1. Initial stages of plate divergence

 

   2. Rift valley floored by new basaltic (oceanic) crust.

 

   3. Further widening of rift, marine waters begin filling valley

 

      B. Young Ocean Basin is Born - A True Sea

 

         1. Continued plate divergence now in full swing

 

   2.True seafloor spreading in operation =  Mini ocean basin

 

          3. Matching set of opposing coastlines frame the sea

 

     C. Full Maturation of Ocean Basin -

 

        1. Divergence begins to stall - spreading rate slows

 

 2. Continental margins, abyssal seafloors, and mid-ocean ridge

 

        3. Fully-developed ocean has emerged with an age 200-400 Ma

 

    D. Mature Ocean Basin Starts to Collapse near Its Margins

 

1. Old, dense ocean lithosphere becomes isostatically unstable

 

2. Subduction initiated; ocean basin lithosphere dives into

       upper mantle forming ocean trenches and island arcs.

 

3. Beginning of plate convergence of sides of ocean basin

 

    E. Collapsing Ocean Basin Becomes Narrow and Irregular

 

        1.  Plate convergence in full swing

 

        2. Subduction zones established along continental margins

 

 3. Extensive volcanic and uplifted mountain chains result

                 from continued subduction and intense collision forces

 

   F. Total Collapse of Ocean Basin - Suturing of Continents

 

        1.  Plate convergence reaches an apex -  subduction wanes

 

        2. Last of oceanic lithosphere subducted - Ocean basin gone

 

        3. Massive thrusted and uplifted mountain ranges form a

              complex continental suture zone marking the site of the

now totally collapsed ocean basin

 

XIV. Paleogeographic Reconstruction

     A. Term used to describe the technique of model-mapping

   ancient geographic settings on Earth, using numerous

   geologic and biologic criteria recorded in rock record:

 

o      Paleomagnetism

o      Paleontology

o      Stratigraphy

o      Paleotectonics

o    Paleoclimatology

 

XV. Tectonically-Controlled Mineral Resources

       A. Divergent Seafloor Spreading Processes

                 1. Massive metal sulphides deposits

o     Hydrothermal vent activity

o     Example: Cyprus, Mediterranean Sea

 

        B. Convergent Subduction Zone Processes

                 1. Porphyry metal lead/sulphide deposits

o     Hydrothermal plutonic activity

o     Example: Bingham, Utah

o     See Figure

 

                 2. Gem vein deposits

o   Plutonic fluid activity

o   Example: Pala District, San Diego County

o  See Figure

                  

       C. Continental Collision Zone Processes

                 1. Petroleum development and concentration

o   Ocean basin collapse

o   Example: Mid-East

 

                 2.  Various mineral and gem deposits

o   Mountain-building processes

o   Example: Himalayas

 

XVI. Seafloor and Plate Tectonics Vocabulary

 

Abyssal plain

Active continental margin

Atoll

Continental margin

Continental rise

Continental slope

Guyout

Isostatic equilibrium

Mid-oceanic ridge

Oceanic trench

Ooze

Ophiolite

Passive continental margin

Pelagic clay

Reef

Ridge fracture zones

Seamount

Submarine canyon

Submarine hydrothermal vent

Submarine fan

Turbidity current

Wilson cycle

Athenosphere

Benioff zone

Continental-continental boundary

Continental drift

Continental margin arc

Convergent plate boundary

Divergent plate boundary

Hot spot

Lithosphere (plate)

Magnetic anomalies

Mantle thermal convection cell

Paleogeographic reconstruction

Pangaea

Plate tectonic theory

Polar wander paths

Oceanic-continental boundary

Oceanic-oceanic boundary

Oceanic ridge

Oceanic trench

Ophiolite

Seafloor spreading

Slab pull

Slab push

Subduction

Transform fault

Transform plate boundary

Volcanic island arc

 

Abyssal plain

Active continental margin

Atoll

Continental margin

Continental rise

Continental slope

Guyout

Isostatic equilibrium

Mid-oceanic ridge

Oceanic trench

Ooze

Ophiolite

Passive continental margin

Pelagic clay

Reef

Ridge fracture zones

Seamount

Submarine canyon

Submarine hydrothermal vent

Submarine fan

Turbidity current

Wilson cycle