Plate Techtonics Flashcards
What does the earth’s plate comprise of?
- Core
- Mantle (Lower mantle, Asthenosphere, Uppermost mantle)
- Lithosphere (Uppermost mantle, crust)
What are the three types of plate boundaries?
- Divergent
- Convergent
- Transform
What is polarity?
-Unlike the geographic North and South, the magnetic North and South shift and reverse over time.
-When both magnetic and geographic norths and souths point in the same direction, they are of normal polarity.
-In opposite directions, they are at reverse polarity.
Explain magnetic stripping and how it occurs.
-Magnetic stripping is a zebra like pattern
-Where strips of normal polarity rocks and reverse polarity rocks alternate on the sea floor
-It is symmetrical on both sides of the mid-ocean ridge.
-The further out it is from the ridge, the older it is.
-It occurs as oceanic plates diverge
-And iron-rich lava erupts from the centre of the ridge
-The lava looses heat and solidifies to form new oceanic crust
-The crust is then pushed away in both directions from the ridge when new lava cools and solidifies.
-When Earth’s polarity reverses, the rocks record the reversals
-Over time, the polarity alternates so the rocks create a strip pattern of different polarity. Reversed and normal.
Example of O-O divergent plate boundary
North American plate and Eurasian plate.
Example of C-C divergent plate boundary.
Nubian plate and Somalian Plate.
Example of O-O convergent plate boundary.
Philippine Plate and Pacific plate.
Example of O-C convergent plate boundary.
Nazca Plate and South American plate
Example of C-C convergent plate boundary.
Eurasian plate and Indo-Australian plate
Example of transform plate boundary.
San Andreas Fault where Pacific plate slides past North American plate.
In C-C convergence, what happens and what is created?
-Folding, uplift, and buckling occurs in the continental plates due to pressure.
-This creates fold range mountains and earthquakes due to the friction from the collision, causing seismic activity.
What happens during O-C convergence, and what is formed?
-Subduction happens and the oceanic plate dewaters due to high heat and pressure.
-The dewatering lowers the temperature of the surrounding mantle material which forms magma that rises through the weak areas/cracks and fissures of the continental plate. This forms volcanoes.
-The subducting plate forms deep sea trench.
-Earthquakes along the subducting Oceanic plate.
What happens and forms at an O-O divergence?
-Decrease in pressure cause mantle below to melt, forming magma.
-Which rises through the cracks and fissures of the crust to the surface of the earth. Fills up with magma —> lava, solidifies and forms new oceanic crust.
-Continues to solidify to form mid oceanic ridge
-volcanic islands+volcanoes
How do earthquakes form?
-The sudden release of energy in lithosphere shakes the ground
-focus is where seismic waves are released (origin of earthquake)
-epicentre where shaking felt most strongly on surface (directly above focus)
What types of seismometers are there?
- Richter Scale (largest wave recorded)
- Moment magnitude scale (total energy released)
