1. Physical Geography by Alan Arbogast Chapter 13
Tectonic Processes
and Landforms
Lawrence McGlinn
Department of Geography
State University of New York - New Paltz
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2. Tectonic Processes and Landforms
Plate Tectonics
Types of Plate Movement
Plate Convergence
Earthquakes
Volcanoes
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Plate Tectonics
Theory that Earth’s crust consists of plates that move individually & collectively
Helps explain location of mtn ranges, earth-quakes, volcanoes & other landforms
First theorized by Wegener in early 1900s
Pangaea – supercontinent that existed 300 my ago – continents spread by Continental Drift
Theory ignored through 1950s – validated in more recent research
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4. Fossil Evidence for Pangaea
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5. Continental Drift Since Pangaea
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6. Mechanisms of Continental Drift
Magma Plume pushes plates
apart
Convection within Earth
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Seafloor Age
Red youngest through green & yellow to blue, oldest
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8. Current Locations & Movement of Plates
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9. Types of Plate Movements
Passive Plate Margins
Transform Plate Margins
Plate Divergence
Plate Convergence
Collision
Subduction
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Passive Plate Margins
Where continental crust and bordering oceanic crust are on the same tectonic plate – tectonically stable
Example of East Coast
of US on North American Plate
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11. Transform Plate Margins
Boundaries where plates slide past each other horizontally
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Plate Divergence
Lithospheric plates moving away from each other
Magma plumes move up & out through plate fractures, plates spread in process called Rifting
As plates spread, Mid-Oceanic Ridge forms from rifting
Active and Passive Margins
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Rifting in East Africa
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Plate Convergence
Collision – two plates of continental crust meet
Crust crumples causing folding of horizontal bedrock layers
Monocline – 1-sided slope rock beds inclined in one direction over large area
Anticline – upward arc of folded rock
Syncline – downward dip in folded rock
Overthrust fault – intense compression shoves one part of rock mass over the other
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Collision and Folding
Folding
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16. Ridge and Valley Evolution
The Folded
Appalachians
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Subduction
Process in which one converging plate is forced beneath another, usu. oceanic plate under continental
Plate Boundary Relationships
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Earthquakes
Sudden release of tectonic stress creates movement in Earth’s crust & shockwaves through lithosphere
Fault – fracture between adjoining plates along which plates can move
Focus – point in lithosphere where fault breaks
Epicenter – point on surface directly above focus
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Earthquake Processes
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Earthquake Energy
Waves released by an earthquake:
P-waves – primary, compressional waves that travel km/sec
S-waves – secondary, vertical waves that travel 60-70% slower than P waves
Difference in arrival time of p-waves and s-waves, helps estimate distance to epicenter
Known distance to 3 stations yields location
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21. Triangulation to Locate ‘Quake
Known distance to stations A, B and C shows location of epicenter
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Seismograph
Records vertical & horizontal motion of Earth, & magnitude of motion
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23. Measuring Earthquakes
Richter Scale – logarithmic measure where each whole number represents 10X the shaking of the next smaller number
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Faulting
Earthquakes occur along faults – cracks in Earth’s crust where rocks or plates are displaced
Fault Types:
Normal – vertical fault, diverging force
Reverse – vertical fault, compressional force
Strike-Slip – horizontal fault, blocks slide past one another – larger scale called Transform
Overthrust – upthrown block slides over downthrown block
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Fault Types
Earthquake
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San Andreas Fault
(Transform Fault)
Movement
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27. Basin and Range Province
From Satellite
Horst & Graben Formation
In Landscape
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Volcanoes
Mts or hills w/ a conduit down into upper mantle through which magma, ash & gases are ejected
3 basic types:
Cinder-cone Volcanoes
Composite Volcanoes
Shield Volcanoes
Volcanoes
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29. Cinder-Cone Volcanoes
Small, steep-sided volcano made of magma fragments & rock debris from central vent
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Composite Volcanoes
Large, steep-sided volcano built up by layers of lava & rock debris – over subduction zones – viscous (low flow), silicate (high gas-explosive think of shaking coca-cola can) magma - explosive eruptions
Cross
Section
Mt. Fuji
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Pacific “Ring of Fire”
Concentration of composite volcanoes around the Pacific Basin over subduction zones
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Shield Volcanoes
Broad, gentle-sided volcanoes formed from low-silica, low-viscosity (high flow) magma – lava flows cool & harden to become basalt
Cross Section
Mauna Loa, Hawaii
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Hot Spots
Stationary points in aesthenosphere from which a magma plume intermittently pushes through the crust above
Plates move over hot spots, carrying deposits of basalt with them
Hawaii (& the Emperor Seamount Chain) & Yellowstone have been shaped by hotspots
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34. Formation of Hawaii Emperor Seamount Chain Hawaii
70 M yrs old – Pac. Plate
1st moved North, then NW
Hawaii
Kauai Oldest – Big Island
(Hawaii) still over hot spot
70 mya
Present
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35. Yellowstone Hot Spot North American Plate has moved west,
then northwest over past 16.5 M yrs
Calderas from eruptions
in past 2 M yrs
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Geyser Cross Section
Old Faithful
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