earthquake
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Earthquakes:
the sudden release of energy in the earths crust caused by the movement of tectonic plates, producing seismic waves
seismic waves
waves of energy that travel through the earth after an earthquake
focus
the point inside the earth where the earthquake starts
epicentre
the point on earths surface directly about the focus
foreshock
a smaller earthquake that occurs before the main earthquake
aftershock
smaller earthquakes that occurs before after the main earthquake as the crust adjusts
2 causes of earthquakes
1) movement of magma beneath the earth 2) faulting 3) elastic rebound
elastic rebound theory
rocks along a fault bend and store energy as plates move. when stress becomes too great, the rocks snap back to their original shape, releasing energy as an earthquake.
shallow focus depth
surface to 70km
intermediate focus depth
70 and 300km
deep focus depth
over 300
primary waves
fast, travel through all
secondary waves
slow, travel though solids
love waves
most destructive
rayleigh waves
cause most shaking
how do scientists know the outer core is liquid
s waves cannot travel through liquids, and they stop when they reach the outer core
richter scale:
measures magnitude
mercalli scale
measured intensity
factors that affect volcanic eruptions
1) magmas composition 2) magmas temperature 3) amount of gas in magma
Three types of volcanos
Shield - wide composite - steep come - small
Basaltic lava
low silica, runny, gentle eruptions
granitic lava
high silica, thick and sticky, explosive eruptions
Yellowstone
Supervolcano, explosive, thick magma
hawaii
shield volcanoes, gentle, runny lava