Forces that Shape the Earth

What is Stress?

• Force that acts on rock to change its shape or volume

• What causes students to freak out on test day

• The definition of Plate Tectonics

• Sea floor spreading

Pulls on the crust, stretching rock so it becomes thinner in the middle

• Tension

• Stress

• Compression

• Shearing

Squeezes rock until it folds or breaks

• Tension

• Stress

• Compression

• Shearing

Pushes a mass of rock in two opposite directions

• Tension

• Stress

• Compression

• Shearing

Example: •Fault zones – an area of many fractured pieces of crust along a large fault

• Tension

• Stress

• Compression

• Shearing

Example: ••Volcanic arcs – curved line of volcanoes that forms parallel to plate boundaries

• Tension

• Stress

• Compression

• Shearing

Example: •Continental rifts – when divergent boundaries occur within a continent, they cause enormous splits in the crust

• Tension

• Stress

• Compression

• Shearing

Example:•Mid-ocean ridges – tension causes oceanic crust to spread allowing hot rock from mantle to rise creating high ridges

• Tension

• Stress

• Compression

• Shearing

Example:•Mountain ranges – collision between two continental plates

• Tension

• Stress

• Compression

• Shearing

Example:•Transform faults – when plates slide horizontally past each other they form a fault, or a break in the rock of the crust

• Tension

• Stress

• Compression

• Shearing