Plate Tectonics Flashcards
(10 cards)
Structure Earth
Core
Inner solid, Outer liquid
Mantle
2.900km thick, thickest section
Crust
Oceanic thinner but more dense
Continental thicker but less dense
Plate Tectonics Earth Structure
Lithosphere
-consists of crust and upper mantle
-Solid and Brittle
Asthenosphere
-upper mantle just below lithosphere
-Solid but will flow
-Where convection currents operate
Geological Evidence for PT
Rock type, age and structure
Similar found thousands of miles away
e.g ancient Caledonian Mtns
Structural trend line that match up if continents side by side on map
Fossil Distribution
Same animals and plants in widely separated continents
e.g. Mesosaurus South America, Africa, India, Antarctica and Australia - Pangea form one continuous band
Climatology
Fossilised remains of polar plants in India, Australia and S.Africa
Fossils of tropical in mid latitudes in Northern Europe
Laid down when continents occupied different positions on surface of Earth
Why was Wegeners theory not widely accepted?
Unable to come up with a process that explained how movement might occur
Ocean Floor Relief
Mid Ocean Ridge & Deep Ocean Trenches
Longest Mtn Range
75000km long
1000km wide
2500m high
Most of major oceans
Ridge has huge rift valley - ocean floor splitting apart
Ocean trenches South America show ocean floor sinking into asthenosphere
Sea floor moving
Age of Sea Floor
As move out from Mid Atlantic Ridge towards continents
Rocks on sea floor get progressively older
Symetrical pattern either side
Paleomagnetism
Earths magnetic pole flips periodically from N to S
As magma cools the iron inside it orientates itself in the direction of the magnetic pole
1960s ships with magnetometers
Discover as you move from MAR there is a symmetrical striped pattern of magnetic orientation
Global Pattern of Earthquakes
Cold war seismometers developed allowed observation of worlds largest earthquakes
Clustered linear pattern across lithosphere, thin narrow bands. Study movement at these lines show litho split into plates
Plates move individually away, toward or along side eachother
