Ask a Geologist:Plate Tectonics
By: Christian Rowan
About MeChristian Rowan ● I am a graduate student in the
Department of Earth and Planetary Sciences.
● I study structural geology.● I like to hike and camp. ● My favorite landscape features
are mountains!
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Plate Tectonics ● Earth’s surface is
broken up into large plates
● These plates move very slowly by processes deep in the Earth
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NASA
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North American Plate
NASA
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Earth’s Structure
Crust(0-100 km)
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Earth’s Structure
Mantle (2,900 km)
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Earth’s Structure
Core (6,378 km)
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Lithosphere (“rocky+sphere”)● Crust + upper most solid mantle● Made up of rock (rigid, hard)
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Asthenosphere (“weak+sphere”)● Upper mantle● Solid but capable of flowing (like Jell-O!)
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The lithosphere “floats on” the asthenosphere due to differences in the properties of the solid (rigid vs. putty-like solid).
Lithosphere
Asthenosphere
Convection currents cause plates to move!
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● Convection in the asthenosphere● Carries heat from Earth’s core to the surface
Heat Source (Flame)
Convection currents in a boiling pot of water
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Plate movement driven by convection currents and slab pull
As plates move around the globe…
What happens when plates encounter each other?
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Plate Boundaries
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Convergent (Plate move together)
Divergent(Plates move
apart)
Transform(Plates move past)
Wikimedia
Plate interactions at boundaries creates the topography we see on Earth!
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Let’s go exploring…
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Where do convergent plate boundaries occur?
Andes Mountains
Himalayas
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Where do divergent plate boundaries occur?
Mid Ocean Ridge
East Africa Rift Valley
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Where do transform plate boundaries occur?
San Andreas Fault
Plates move very, very slowly
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● 2-5 centimeters per year ● Comparable to the the rate
of fingernail growth! Given enough time, plates moving very slowly can form supercontinents like Pangea!
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Global Paleogeography: Present Day to 600 Ma
All images: coyright Ron Blakey, Northern Arizona University & Colorado Plateau Geosystems, Inc.
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Present
Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
Pleistocene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
20 Ma: Neogene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
35 Ma: Oligocene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
50 Ma: Eocene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
65 Ma: K/P boundary
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
90 Ma: Late Cretaceous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
105 Ma: Cretaceous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
120 Ma: Early Cretaceous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
150 Ma: Late Jurassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
170 Ma: Jurassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
200 Ma: Early Jurassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
220 Ma: Late Triassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
240 Ma: Early Triassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
260 Ma: Late Permian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
280 Ma: Early Permian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
300 Ma: Late Carboniferous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
340 Ma: Early Carboniferous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
370 Ma: Late Devonian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
400 Ma: Early Devonian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
430 Ma: Silurian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
450 Ma: Late Ordovician
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
470 Ma: Middle Ordovician
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
500 Ma: Late Cambrian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
540 Ma: Early Cambrian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
560 Ma: latest Proterozoic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
600 Ma: Late Proterozoic
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Now let’s go forward in time from 600 Ma to the Present!
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
600 Ma: Late Proterozoic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
560 Ma: latest Proterozoic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
540 Ma: Early Cambrian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
500 Ma: Late Cambrian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
470 Ma: Middle Ordovician
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
450 Ma: Late Ordovician
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
430 Ma: Silurian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
400 Ma: Early Devonian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
370 Ma: Late Devonian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
340 Ma: Early Carboniferous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
300 Ma: Late Carboniferous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
280 Ma: Early Permian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
260 Ma: Late Permian
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
240 Ma: Early Triassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
220 Ma: Late Triassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
200 Ma: Early Jurassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
170 Ma: Jurassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
150 Ma: Late Jurassic
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
120 Ma: Early Cretaceous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
105 Ma: Cretaceous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
90 Ma: Late Cretaceous
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
65 Ma: K/P boundary
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
50 Ma: Eocene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
35 Ma: Oligocene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
20 Ma: Neogene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
Pleistocene
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Image: coyright Ron BlakeySlide courtesy of: Roy Schlische
Present
Why Do We Care?
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Geohazards ● Earthquakes are caused by the movement of plates!
Why Do We Care?
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Evolution● The movement of plate helps us understand the
evolution of plants and animals!
Why Do We Care?
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Long-term climate ● The creation, destruction, and movement of
continents/oceans has great influence on long-term climate change.
Question Time!