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Class 1: Plate Tectonics Review
Today’s topics:
 Earth’s compositional layers
 Plate tectonics: theory & actions
Earth’s Compositional Layers
Atmosphere & Hydrosphere
Crust
Mantle
Core
Earth’s Atmosphere & Hydrosphere
Earth’s Crust
more dense
CRUST
relatively light
Earth’s Mantle
CRUST
more dense
than crust
MANTLE
Earth’s Core
CRUST
MANTLE
highest
density
CORE
Earth’s Magnetic Field
Requirements for magnetic field:
1. rotation
2. heat flow, convecting fluid
3. a mobile conductor (iron or metallic hydrogen)
Earth
rocky core
Global Earthquake Locations
Global Volcano Locations
Linking Observations
Continental Drift
Continental Drift (movie)
Ages of the Ocean Floor
Ma = Million years ago
1 billion years = 1 Gyr
1 million years = 1 Myr
1 thousand years = 1 kyr
Heat Flow
high at
ocean ridges
Warm colors = higher heat flow
Cool colors = lower heat flow
Global Topography and Bathymetry
ocean
ridges
The Puzzle Solved…..
earthquake locations
sea floor age
volcano locations
sea floor bathymetry
+ heat flow too!
Earth’s Tectonic Plates
Earth’s Tectonic Plates (movie)
Lithosphere & Asthenosphere
Plate Boundaries
Divergent Plate Boundaries
Seafloor Spreading (movie)
Convergent Plate Boundaries
2
1
3
Seafloor Subduction (movie)
Transform Plate Boundary
strike-slip
faulting
Transform Faulting (movie)
Plate Boundaries
Hotspots
Hot Spots
hot spot trail
Formation of Island Chains
V1
Direction of plate motion
lithosphere
melting at base
of crust
V1
V1
Hot (not molten)
rising plume
Formation of Island Chains (movie)
Example: The Hawaiian Chain
Fixed
hot spot
Basic Premise of Plate Tectonics
• Earth’s crust is divided into plates
• Plates move relative to one another at 1-15 cm/yr
• Plate interiors are largely undisturbed
• Deformation is concentrated at plate boundaries
Consequences:
• Plate tectonics constantly change Earth’s surface
• Earthquakes occur mostly at plate boundaries
• Volcanoes occur mostly at plate boundaries
How do we explore Earth’s interior?
1. Examine volcanic rocks
Q: what was the source for magma?
2. Observe seismic waves from earthquakes
Q: where are the layers, what are their densities?
3. Examine meteorites
Q: what are they made of? like the core?
4. Existence and behavior of geomagnetic field
Q: what is the core doing?
Earth
Satellites
• Size (radius)
• Bulk density
• Surface gravity
• Tectonism, volcanism
• Rotation
• Orbit
• Atmosphere
• Surface pressure
• Surface temperature
• Plate tectonics
• Water
•
1 (Moon)
6378 km
5.5 g/cm3 (4.1 g/cm uncompressed)
9.8 m/s2
yes (today)
1 day
365.25 days
78% N2, 21% O2
1 atm
20°C (diurnal, seasonal changes)
yes
yes
3