Mountain Building

1. Mountain Building Sturdivant

2. Forces within Earth • Deformation – any change in a rock’s shape (bending/breaking) • Stress – force acting over some area of rock (tension, compression, and shearing) • Strain – deformation of rock caused by stress • Rocks will deform in different ways depending on temperature, pressure, rock composition, and time

3. Types of deformation • Brittle – at low temperature and pressure, rocks fracture due to stress • Ductile – at higher depths, rock may bend and warp without fracturing

4. Geologic features from stress • During events such as mountain building, huge stresses are applied to rock • These stresses cause folds in the rock • Anticline (see a) • Syncline (see b) • Monocline (see c)

5. More Geologic features from stress • As stresses are often associated with movement, we also see faults where stress is high • Normal Fault – tensional stress • Reverse Fault – compressional stress • Strike-Slip Fault – Shearing Stress

6. Types of mountains • Folds and Faults together form many of the types of mountains on earth • Volcanic Mountain – formed due to igneous activity (Mt. Saint helens) • Folded Mountain – formed by compressional stress (alps) • Fault-Block Mountain - formed by tensional stress (Sierra Nevada) • Dome Mountain – dome shaped, formed as rock is upwarped (Black hills, SD)

7. Mountains at plate boundaries • Convergent boundary mountains – ocean-ocean and ocean-continent convergence produces volcanic arcs (Philippines and the andes mountains) • Folded mountains are formed at ocean-continent boundaries as well, but our most notable folded mountains (Himalayas) form at continent-continent boundaries

8. Mountains at plate boundaries (continued) • divergent boundary mountains – most often at the ocean floor, divergent boundaries allow for magma to rise and form mountains • Non-boundary mountains – some mountains are away from plates (such as Hawaii formed at local hot spots) and… the rocky mountains

9. Formation of rocky mountains