Fact 1: Faulting of rock in Earth 's crust causes earthquakes.

Fact 2: Faults are produced by stress in the earth's crust that either compress or extend rocks.

Given the two facts above, answer the question "What in the Earth's crust causes earthquakes?" with the following options: 
- heat
 - stress
 - cracks
 - volcanoes
 - erosion
 - waves
 - Wind
 - Movement


 

  stress       