Forces in Earth’s Crust Chapter 6 Section 1

Earthquakes Elasticity is the ability for an object to return to or keep its original shape Which is more elastic… a bouncy ball or a bowling ball?

Earthquakes Elastic limit – the most that something can be stretched or bent before breaking

Earthquakes Tectonic movements supply the force that bend and stretch rocks When the elastic limit of rock is passed, it breaks and produces forces called earthquakes. 80% of all earthquakes occur along edges of the Pacific Plate (Ring of Fire)

Faults the place where rocks break and move by one another There are 3 types of faults

Normal Faults Caused by tension forces Example: Sierra Nevadas

Normal Faults Hanging Wall

Reverse Faults Caused by compression forces Example: Himalayas

Reverse Faults Hanging wall

Strike-Slip Fault Caused by shearing forces Occurs at transform boundaries Irregular surfaces snag each other Example: San Andreas Fault

Strike-Slip Fault

Let’s Review What are the 3 kinds of faults? –Tension –Compression –Shearing What are the 3 kinds of forces that cause faults? At what boundaries do they form? –Normal –Reverse –Strike-slip Divergent Convergent Transform

Earthquakes can be dramatic or almost unnoticed

Changing Earth’s Surface Sometimes plate movements cause the crust to fold (mountain building)

Changing Earth’s Surface Stretching can cause fault-block mountains

Changing Earth’s Surface Large, flat, blocks of rock can be pushed upward – high above sea-level (plateau)