Earth structure
-inner core: solid 5100km thick very hot mainly composed of iron generates convention currents a solid
-outer core: liquid due to heat of core moves around the inner core creates earths magnetic field
-mantle thickest earths layer
-upper mantle made up of asthenosphere tectonic plates are formed solid
Lithosphere semi-molten flowing slowly
-crust: thin and rigid made from oceanic and continental
What does heat from the core create?
Convection currents
Ridge push
A gravitational force that Occurs at mid ocean ridges at constructive plate boundaries
Molten wells up at diverging plate partial melting of upper mantle
where newly formed lithosphere forms an elevated ridge
As lithosphere cools it slides down the slope due to gravity pushing the tectonic plates away from the ridge
Oceanic vs continental
- C is older
- O is more dense
-O is basaltic and C is granitic
-C is thicker
Slab pull
Occurs at subduction zones where denser oceanic plates away sink into the mantle and pulls the remainder of the plates along
At destructive boundaries
90% of worlds earthquakes
Converging
What formed earths structure
-collisions of clouds of dust and gas
-meteorite collisions
What causes movement of tectonic plates
Convection currents
Divergent
Mid ocean ridges
Move away from each other
Oceanic plates
Shield volcanoes
Less powerful earthquakes
Slab pull
At subduction zones
Denser oceanic plates sink into mantle
Destructive
Convergent boundary
Move towards
Oceanic and continental
90% Earthquake
volcanoes composite
Subduction
Conservative
Continental plates drag past eachother
Earthquakes no volcanoes
What is focus and epicentre
Focus= below the surface the
Epicentre= on the surface directly above focus
Body waves
Travel through earth before surface waves
-Primary waves slinky movement fastest first waves to arrive caused by compression
-Secondary waves skipping rope shake slower but cause lots of damage
Surface waves
Travel only through the crust mist destruction
-Love waves side to side fastest move ground side to side greatest damage
-Rayleigh waves up and down felt the most moves ground up and down
Ways to predict volcanoes
-monitor microquakes
-changes in ground levels
-gass measurements collection through fumaroles
-seismic activity
-cone temp
How Philippines monitor
-1984
-timely alerts
And hazard mapping and risk assessments
Land use planning
Identify most hazardous areas and avoiding to overly high density the area
Hotspots
Away from plate boundaries
Caused by plumes of superheated magmas
Rising from the asthenosphere
Crust may be thin or weak and escape into the surface as an eruption
E.g Hawaiian islands
Magnitude of earthquakes
Most important influence on the severity
Measured by MM scale
Richter scale based on amplitude
Magnitude of volcanic
Exclusivity index
Total volume ejected
Height of eruption cloud
Duration of main eruptive phase
Predicting earthquakes
-microquakes
-bulging of the ground
-raised groundwater levels
-curious animal behaviour
