1.2 THEORETICAL FRAMWORKS AND PLATE MOV Flashcards
what is the thin oceanic crust composed of?
-basalt
what is thicker continental crust composed of?
-granite
what does the earth’s mantle have?
-a temp gradient
in the upper mantle what are rocks like?
-cool
-brittle
in the lower mantle what are rocks like?
-hot
-plastic
in upper mantle how are earthquakes caused?
-bcoz the rocks are brittle enough to break and produce them
how are convection currents driven?
bcoz radioactive decay rises within the mantle, driving convection currents to then move tectonic plates
what is seafloor spreading?
-it occurs at divergent plate boundaries
-under the ocean
-it’s the continuous input of magma forming a mid-ocean ridge
-e.g mid-Atlantic ridge
what does gravity cause in terms of crusts?
-causes denser oceanic crust to be pulled down at site of subduction
what is slab pull?
-pulling force exerted by cold, dense oceanic plate plunging into mantle due to own weight
whats ridge push?
-proposed driving force for plate motion in plate tectonics
-occurring in mid-ocean ridges
-as a result of lithosphere sliding down the asthenosphere
what is the Benioff zone?
-an area of seismicity corresponding with the slab being thrust downwards in a subduction zone
palaeomagnetism? (4)
-results from zone of magma locking in the earths magnetic polarity when it cools
-scientists use this tool to determine historic periods of large scale techtonic activity
-through reconstruction of relative plate motions
-creating a geo timeline
subduction zones? (5)
-where 2 plates come together
-more dense oceanic plate subducts the continental plate
-2 plates lock together causing frictional stress
-causing failure along fault planes which results in a mega-thrust earthquake
-releasing strain energy and seismic waves
locked fault?
-fault that’s not flipping because the frictional resistance on fault is greater than shear stress across fault
-stress can be stored and then released as earthquakes
-e.g the 2004 Indian Ocean tsunami
