structure of the earth tectonics
Download
Skip this Video
Download Presentation
Structure of the Earth Tectonics

Loading in 2 Seconds...

play fullscreen
1 / 48

Structure of the Earth Tectonics - PowerPoint PPT Presentation


  • 60 Views
  • Uploaded on

Structure of the Earth Tectonics. Chapter 22 ISCI 2001. Structure of the Earth. Crust. (1). Thin, brittle Oceanic Basalt rock (dark); greater density Continental Granitic rock (lighter); less dense Less dense than mantle Floats. Mantle. (1). Most of the volume (82%) and mass (65%)

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Structure of the Earth Tectonics ' - margie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
crust
Crust
  • (1). Thin, brittle
    • Oceanic
      • Basalt rock (dark); greater density
    • Continental
      • Granitic rock (lighter); less dense
    • Less dense than mantle
      • Floats
mantle
Mantle
  • (1). Most of the volume (82%) and mass (65%)
    • Thickest layer
  • (2). Rich in Si and O
    • Contains Fe, Mg, Ca (causes increased density)
      • Density increased by weight of crust also
  • (3). Hotter than crust
    • High pressure
      • Caused by radio active decay of elements
      • Flow of heat from core
  • (4). Regions – Upper Mantle
    • Lithosphere
      • Stiff, cool – similar to crust (forms one layer together)
    • Asthenosphere
      • Solid, plastic (solid flow)
  • (5). Upper Mantle
    • Solid and rigid
    • Plastic but not as much as upper mantle
slide5
Core
  • Consist of:
    • Metallic Fe
    • 2x dense as mantle
  • (2). InnerCore
    • Solid
    • 4000 to 7000 C
      • Radioactive elements
      • Earth development; matter hitting the surface
      • Core sinking to the center
  • (3). OuterCore
    • Flows due to less pressure
    • Rotation of Earth stirs up core material
      • Produces magnetic field (flowing electrical charge)
plate tectonics
Plate Tectonics
  • (1). Continents sit atop of tectonic ‘plates’
    • What are the plates made of?
    • What is a continent?
  • (2). Plates
    • Consist of mantle and the crust (lithosphere)
    • Plates move atop the asthenosphere (plastic)
      • Continents move because they are embedded into the plates
  • (3). Plateboundaries and continents
    • Continents and plates do not have the same boundaries (overlapping) Figure 22.18
    • A lot of action occurs at the plate boundaries!
how were the plates discovered
How were the Plates Discovered?
  • (1). AlfredWegener
    • Proposed the theory of “Continental Drift”
      • Continents are in motion; drifting over geologic time
    • Pangea (figure 22.8)
    • Same fossils found in several different continents
    • Matching rocks on both sides of Atlantic Ocean
  • (2). Evidence for CD
    • Seafloor Spreading
    • Magnetic Stripes
evidence for continental drift seafloor spreading
Evidence for Continental Drift –Seafloor Spreading
  • (1). Magma flows out of breaks in lithosphere
    • New lithosphere is formed and old lithosphere will be recycled back in trenches (22.16)
      • Mid-ocean ridge
    • Pushes the continents in specific directions
evidence magnetic stripes
Evidence – Magnetic Stripes
  • (1). Lava contains Fe and magnetite (Fe and O)
    • Crystals are magnetic – line up with the magnetic field of the Earth
      • Crystals point North and south / cool and freeze and become locked in
      • Contains a record of the history of the magnetic field of the Earth
      • Gives a striped, bar pattern (22.17)
      • Alternates normal (today’s field) and reversed field from years ago.
      • Runs along the spreading seafloor
how do the plates move
How do the Plates Move?
  • (1). As magma is heated deep in the Earth it moves upward via convection currents (22.21)
    • Hot rocks from lower mantle move upward cool in the upper mantle and return
    • Hit the lithosphere and can crack it – seafloor spreading
    • Plates move atop ‘convection cells’
plate tectonics1

Plate Tectonics

ISCI 2001

Chapters 22-24

plate activities divergent plate boundaries
Plate Activities – Divergent Plate Boundaries
  • (1). Plates may ‘diverge’
    • Plates move apart
      • Lava fills spaces in between
  • (2). What types of structures are produced?
    • Volcanic mountains
    • Rift valleys
  • (3). Examples
    • Mid-Atlantic Ridge
    • Great Rift Valley (Africa near Nairobi Kenya)
convergent boundaries
Convergent Boundaries
  • (1). When two plates collide
    • One plate usually subducts
      • Most dense or oldest plates
oceanic oceanic
Oceanic – Oceanic
  • Trench formation (Marianas Trench)
    • 11,000 m or 7.0 miles deep
      • Pacific and Phillipine Plates collide
      • Formation of volcanic islands or arcs
        • Subduction plate mantle rock melts comes to the surface and cools
oceanic continental
Oceanic – Continental
  • Oceanic – Continental
    • Oceanic basaltic plate (more dense) subducts under granitic continental plate
    • Mantle rock melts, magma rises and cools forms island chains
    • Volcanic Arcs (Peru)
oceanic continental1
Oceanic – Continental

The convergence of the Nazca and SouthAmericanPlates has deformed and pushed up limestone strata to form the towering peaks of the Andes, as seen here in the Pachapaqui mining area in Peru.

continental continental
Continental – Continental
  • Continental – Continental
    • Massive plate collisions (both granitic)
    • No subduction, why?
      • Both have same density
    • Massive mountains are formed
      • Himalayas
transform plate boundaries
Transform Plate Boundaries
  • (1). ‘Sliding Plate’ Boundaries
    • Slipping of plates causes ‘faults’
  • (2). Slipping causes plate movements
    • Boundaries move in opposite directions against each other
  • (3). Where are they normally found?
    • Mostly ocean basins
    • Continental plate: San Andreas Fault
faults
Faults
  • Parts of a Fault
  • Normal Faults
    • Dip-slip
  • Reverse Faults
  • Strike-Slip
types of faults
Types of Faults
  • (1). Dip-Slip (See figure 24.5)
    • Hanging wall and vertical wall move vertically along the fault plane
      • Movement is vertical
  • (2). Strike-Slip
    • Movement is horizontal
    • San Andreas Fault motion
  • (3). Oblique
    • Move horizontally and vertically
slip dip
Slip-Dip

Conjugate Normal faults, Canyonlands National Park, Utah

folding
Folding
  • (1). Bending in Rock layers
    • Caused by compression
  • (2). Results
    • Anticlines or synclines
mountain formation
Mountain Formation
  • (1). Folded Mountains
    • During formation continental crust thickens and wrinkles into vertical folds from compression
      • Appalachians, Rockies and Himalayas
  • (2). Unwarped
    • Domed shaped
      • Single anticline (crust is heaved upwards; no folds produced)
      • Adirondack mountains NY
  • (3). Fault-Block
    • Land is ‘uplifted’ , stretched and elongated
    • Very steep profile
    • Tetons (Wyoming); Sierra Nevada (California)
mountain formation1
Mountain Formation

Folded Mountain – Antarctica

mountain formation2
Mountain Formation

Adirondack Mountains – unwarped

consequences of plate movements
Consequences of Plate Movements
  • (1). Earthquakes
    • Transform faults
      • Compression and tension caused by stress of plate movements -- Slipping
        • Focus location
      • Rock is snapped or broken releasing ‘elastic’ energy
  • (2). Types
    • Intraplate (10%)
      • Away from plate boundaries
      • New Madrid, Missouri
    • Interplate (90%)
      • Plate boundaries
        • Transform plates (mild Eqs)
        • Subduction zones (strong)
subduction zones ring of fire
Subduction Zones – Ring of Fire!

80% of all interplate EQs occur here

powerful interplate eqs and tsunamis
Powerful Interplate EQs and Tsunamis
  • (1). Coast of Sumatra
    • Indian and Burma Plate collision
    • Megathrust quake
      • 100 billion tons of TNT
  • (2). Production of a Tsunami
    • Quake took place in the Indian ocean
    • As subduction occurred
      • The seafloor bent as the other plate sank
      • Stress caused rock to snap and thrust upwards
        • Force caused water to creat large wave
        • 30m +/- above sea level
magnitude of earthquakes richter scale
Magnitude of Earthquakes –Richter Scale
  • (1). Logarithmic scale
    • Each point represents a 10-fold increase in quake shaking strength
      • Measures shaking
      • Also indicates 30 fold increase in energy output
    • 1 thru 10
  • Examples
    • 1906 San Francisco (8.2)
    • Sumatran 2004 (9.0)
sumatra eq and tsunami
Sumatra EQ and Tsunami

184,000 People died

ad