Who was Alfred Wegener?
- continents not fixed but instead ‘floating’ on denser material in the mantle below
- continents constantly breaking apart and rejoining in new combinations
What evidence is there for continental drift?
- the fit of the continents
- fossil distribution
- geological evidence (mountain ranges, ancients glaciers and coal deposits)
- living species
What makes up the lithosphere?
Crust and the upper part of mantle
What cause the tectonic plates to move?
Convection currents in the mantle cause the plates to move (hot, less dense magma rises while cooler, heavier magma sinks)
What are the three types of plate boundaries?
Divergent, transform, convergent
Divergent
- spreading
- magma from mantle spews onto earths surface and forms ridges
- results in mid-oceanic ridges
Convergent
- collision
- one oceanic and one continental = subduction
- two continental =formation of mountains
Transform boundaries
- sliding
- plates slide past eachother usually causing earthquakes
How do earthquakes occur?
When tectonic plates are jammed together for a long period of time and suddenly slip releasing a massive amount of energy.
Focus of earthquake
Where the earthquake occurs below the surface
Epicentre of earthquakes
Where earthquakes occur above surface (above focus)
What are the vibrations caused by earthquakes called?
Seismic waves
Measuring/detecting/locating earthquakes
- seismogram uses p and L waves to indicated the intensity of earthquake
- location is found by comparing time between p and s waves
P- waves
- primary
- compression waves
- first to hit seismometer because they are the fastest
- body wave
S-waves
- secondary
- transverse waves
- come after p-waves
- body wave
L-waves
- surface waves
- slow
- cause damage because they distribute their energy across earths surface rather than earths interior
Shield cones
- low domes
- no explosive eruptions because lava is runny therefore gases escape
- made of layers of basalt that formed from very fluid, fast cooling lava
Cinder cones
- pointed shape
- formed only after a few eruptions
- made of pyroclastic material (ejected materials e.g cinder, ash and volcanic rocks)
Composite cones
- steep sides
- made of alternating layer of lava and pyroclastic material
Where can volcanoes be found?
- ring of fire (pacific plate)
- hot spots above mantle plume
- plate boundaries
Earths structure
1) inner core
2) outer core
3) mantle
4) crust
Define magma
Magma is molten rock underground
Define lava
Magma that comes out in the volcano
Define vent
An opening exposed on the earths surface where volcanic material is emitted
