[Unit 1: Enquiry Question 1] Flashcards
Tectonics
Constructive (divergent) boundary
A plate boundary where two plates move away from each other. Plates move by sea floor spreading. magma rises from mantle creating new crust which pushes the plates further apart.
DRC on boundary, mt nyiragongo
Collision plate boundary
A plate boundary where two (continental & continental) plates move toward each other, neither can subduct. so they both crumple and form mountains (e.g. Himalayas)
destructive boundary
A plate boundary where two (oceanic & continental OR oceanic & oceanic) plates move toward each other, the more dense one subducts. Moves via slab pull
cause deep ocean trench, fold mountains, earthquakes (tsunamis).
Conservative boundary
Where two tectonic plates slide past each other, but where crust is neither formed or destroyed. earthquakes form from the friction build up (e.g. San Andres Fault)
Intra-plate earthquakes
These occur in the middle or interior of tectonic plates and are much rarer than boundary earthquakes. ancient fault lines are reactivated forming seismic waves. Some may form new plate boundaries. weakened crust cracks under pressure
Intra-plate volcanoes
formed at hotspots, this is fed by a mantle plume which is an area with really hot and low density magma. This breaks through the crust and forms a volcano
Slab Pull
the pulling of a tectonic plate as its edge subducts deep into the mantle. denser oceanic plates subduct at cold downwellings. This causes cooler mantle areas. affecting convection
Oceanic Crust
7km deep. 28-400°C. low. Basalt. Solid
Continental crust
70km thick. 28-400°C. low. Granite. Solid.
Mantle
700-2890km thick. 870°C. medium. Peridotite. Solid & liquid layers
Outer Core
2890-5150km thick. 4400-6100°C. dense. Iron (mainly) and sulphur. Liquid generating magnetic field.
Inner Core
5150km-centre. 7000°C (radioactive decay). very dense. Iron (mainly) & nickel. Solid
Structure of the Earth (Chemical & Physical layers)
Oceanic crust (basalt)
Continental crust (granite)
Mantle (Peridotite)
Lithosphere - crust + upper mantle
Asthenosphere - upper mantle
mesosphere - (lower) mantle
How do plates move (divergent boundary)?
divergent plate boundaries - the crust thins as it is pulled apart, mantle rises to fill gap. This creates new seafloor. This new seafloor pushes the plates apart on either side.
How do plates move (destructive boundary)?
the less dense plate subducts into the mantle.
the older/cooler rock pulls the plate into the mantle behind it
(slab pull)
what discovery was made for tectonics in 1915
Alfred Wegner - theory of continental drift.
-fossils oceans apart (same green plants) on all continents (once all had same climate)
-mountain ranges have similar rock types. Pangea lines them up as one big mountain range
-What causes continents to move? Scientists mocked it.
what discovery was made for tectonics in 1918
Sonar tech developed.
Map ocean floor (thought it was flat at first)
They were now aware of crust under ocean (ocean floor move)
Belief isn’t credible but gaining support
what discovery was made for tectonics in 1919
Arthur Holmes - suggests convection currents in mantle
-upwards ruptures surface
-downwards causes buoyant continents to crumple into mountains
-lateral moves surface like conveyor belt
what discovery was made for tectonics in 1946
Ocean floor mapped completely.
-mid oceanic ridge
-mountains
-volcanoes
-deep ocean trenches
what discovery was made for tectonics in 1954
J.P.Ruthé - Map of volcanic eruptions & earthquake zones
what discovery was made for tectonics in 1960
Harry Hess & Robert Dietz - sea floor spreading theory
what discovery was made for tectonics in 1963
pattern of magnetic striped rock. Provides evidence for seafloor spread theory.
what discovery was made for tectonics in 1965
J.Tunzo Wilson - plate tectonics theory
what discovery was made for tectonics in 1983
GPS available for public use to track movement of Earth’s surface.
