Mountain Building Sturdivant

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

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

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)

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

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)

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

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

Formation of rocky mountains