Earthquakes and Volcanoes

Layers of The Earth

Tectonic Plates

• The Earth's surface is made up of a series of large plates (like pieces of a giant jigsaw puzzle).
• These plates are in constant motion travelling at a few centimetres per year.
• Convection currents beneath the plates move the plates in different directions.
• The source of heat driving the convection currents is radioactive decay which is happening deep in the Earth.

Three Ways that Plates Move

• destructive plate boundary - two plates move together
• constructive plate boundary - two plates move apart
• conservative plate boundary - two plates move side by side

Earthquake Key Terms

• Earthquake - violent shaking of surface cause by sudden release in tension
• Epicentre - Point on Earth's surface directly above surface where earthquake is felt
• Seismic Wave Energy - Energy released as a shock through crust
• Focus - Point inside crust where built up pressure is released
• Faults - Large cracks in crust
• Magnitude - Unit of measurement for how much energy is release by an earthquake
• Richter Scale - Scale used to measure magnitude of earthquake
• Tsunami - a giant wave or series of large waves in the ocean 
• Liquefaction - process in an earthquake when the movement of energy waves causes the ground to act like a liquid
• Intensity - a measure of the effect of an earthquake
• Aftershock - smaller earthquakes that occur after main quake
• Foreshock - Smaller earthquakes that occur prior to earthquake

Responding to Earthquakes

• Predict - tiltmeters (change in gradient of volcanoes)
• Protect - sit under a table or inside a cupboard
• Prevent - redesign buildings to be earthquake proof.

San Andreas Fault Line

Earthquakes occur quite often along the San Andreas Fault Line because the two plates - North American Plate and the Pacific Plate are of the conservative type of plate boundary which means that they moev side by side to create a lot of friction. Moreover, they move at different speeds; the Pacific Plate moves at 3cm/yr while the North American Plate moves at 1.4cm/yr. Eventually, the friction causes a lot of pressure to…