Studied by 1 personRheological Boundaries
Defined by physical properties at different pressures (depths) and temperatures
Lithosphere, Asthenosphere, Mesosphere, Outer Core, Inner Core
Compositional Boundaries
Defined by chemical composition at different pressures (depths) and temperatures
Crust, mantle, core
Seismic Waves
Change direction at boundaries as they travel through the Earth
S-waves and P-waves
S-waves
Not able to travel through liquids
No s-waves travel through the core
Motion is up and down or front to back
P-waves
Able to travel through solids and liquids
Can make it through liquid outer core
Mantle
Lower part of the lithosphere
Upper mantle layer allows all ridged stuff above it to move
Crust
Upper part of lithosphere
Oceanic Crust
Thin
High density
Young
Continental
Thick
Low density
Young-to-old
Tectonic Plates
Move along the boundary between the lithosphere and asthenosphere
Motion of plates is responsible for creation of ocean basins, mountain belts, volcanic islands, etc.
Lithosphere
Composed of rigid plates that move, controlled by forces in the aesthenosphere (tectonic plates)
Hypothesis of History of Plate Tectonics
Continents collided in the past to form a large landmass (Pangea); have since moved into their present positions
Evidence of Plate Tectonics
Glacial deposits/glacial striations correlate across many continents
Fossils can be traced across continents
Rock and mountain belt similarities between continents
Features of Plate Tectonics
Mid-ocean ridges
Subduction Zones
Mid-ocean ridges
Seafloor mountains created through hot molten getting pushed up, that crystalizes and cools to create a crust
Shallowish depth
Subduction Zones
Seafloor trenches
Deepest parts of the ocean
Magnetite
A brown-black magnetic mineral often found in basalt
Continental Rocks
Can be used to test ages of rocks across the land through absolute and relative dating techniques
Paleomagnetism
Study of the Earth’s magnetic field recorded in rocks
Relies on fact that rocks retain Earth’s magnetic field signature over time
Magnetite and Pyrrhotite
Have the most magnetic character of all minerals on the earths surface
Magnetic Force Lines
Point into and out of magnetic north and south pole
Inclination (how steep angles are) is high near poles and lower near equator
Magnetic Polarity Reversal
Earth’s magnetic field will ‘flip’, and has done so many times in the past
Causes north and south magnetic poles to swap positions
Dangerous
Why is there so little sediment on the ocean floor?
New material on the ocean floor is predominantly basalt from mid-ocean ridges
Why are fossils on the sea floor no more than 200 million years old?
There is no current oceanic crust older than 200ma
Where does geological activity such as volcanoes and earthquakes take place
Plate boundaries
Three types of plate boundaries
Divergent
Convergent
Transform
Divergent Plate Boundaries
Where tectonic plates move apart from each other
Oceanic crust created
Convergent Plate Boundaries
Where tectonic plates move towards each other
Oceanic crust destroyed
Transform Plate Boundaries
Where tectonic plates move along each other
Creates strike-slip faults
Oceanic crust preserved (not created or destroyed)
Three types of convergent margins
Ocean-continent
Ocean-ocean
Continent-continent
Hypotheses for the main driver for actual plate motion
Ridge push and slab pull
Note
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