Earthquakes

Where they occur

• along a crack or fracture in the Earth (fault)
• along plate boundaries
• on land AND in the ocean
• Near volcanoes

Frequency

• More likely at Transform and Convergent
• happen when pressure is released along plate boundaries or faults

Under Pressure

• Pressure or stress can build up.
• Too much pressure = quick movement and release of the energy that is stored

Faults

• created by stress in rocks
• a break in the crust where slabs of crust slip past each other

Types of Stress

• Shear
• Tension
• Compression

Divergent

• Plates move away from each other
• No build of pressure
• Occur less often, but are possible
• Shallow Quakes
• Tension Stress

Convergent

• Plates move towards each other
• Caused by compression forces
• Shallow and Deep quakes
• Can create large earthquakes

Transform

• Shear force
• Example: San Andreas
• Pressure build up
• Shallow earthquakes
• Can be strong in magnitude

Volcanic Explosions

• Magma exerts pressure on the rocks until it cracks
• Magma squirts into the crack and starts building pressure
• Eventually a small quake may form