Forces in the Earth’s Crust

Types of stress Tension, compression, and shearing Over millions of years these have changed the shape and volume of rock Most changes occur slowly and cannot be observed directly…. Fast forward over billions of years and you could see………. Stretching, breaking, tilting, folding, and sliding.

Tension Stress force that PULLS on the crust Stretching rock so that it becomes thinner in the middle Two plates moving apart

Compression Stress force that squeezes rock until it folds or breaks Two plates PUSHING against another

Shearing Stress force that pushes a mass of rock two opposite directions Causes to break, SLIP apart, change its shape

Kinds of faults Most occur along plate boundaries 3 types: normal, reverse, and strike-slip Normal- tension pulls crust apart Reverse- compression pushing together Strike-slip- shearing past each other or up and down

Changing Earth’s Surface Over millions of years the forces can change a flat plain into landforms… Anticlines, synclines, folded mountains, plateaus

Folding Earth’s crust Anticline- rock that bends upward into an arch Syncline- rock that bends downward into a valley

Stretching Earth’s Crust When two plates move away from each other tension creates 2 normal faults When these two normal faults form parallel to one another a FAULT BLOCK MOUNTIAN is formed

Uplifting Earth’s Crust Forces that raise mountains can also UPLIFT and form plateaus

Compression Convergent Boundary Volcano, Mountains Tension Divergent Boundary Sea-floor spreading(trenches and ridges), valley Shearing Transform Fault Boundaries Earthquakes