1. OPHIOLITE Ophiolite (Gk. Ophio – snake; lite- stone from Gk. Lithos) Ophiolite- distinctive assemblage of mafic plus ultramafic rocks; fragments of oceanic crust emplaced at convergent boundary onto continental margins and island arcs. Ophiolite sequence from bottom to top includes peridotite, gabbro(often layered), mafic dikes & pillow basalt, frequently overlain by pelagic/oceanic sediments of bedded chert, mudstone, limestone & graywacke sandstone.

3. Tectonic Regimes – individual components that interact in plate tectonic theory. Six Tectonic Regimes 1. Cratons (Stable Continents) – composed of light-weight rocks that float above sea level on hot plastic interior asthenosphere. Rocks are felsic & intermediate igneous rocks like granite & diorite or their equivalents schist & gneiss

4. 2. Ocean basins – composed of heavy mafic rocks like basalt & gabbro. Ocean basins are composed of the ophiolite suite, a multilayered sequence of rocks. 3. Divergent plate boundaries – new crust is created – ophiolite suite 4. Convergent plate boundaries – crust is destroyed by descending into subduction zone where volcanoes are associated

5. 5. Transform plate boundaries – plates slide past one another; faulting occurs along transform boundaries like Philippine Fault, San Andreas Fault. 6. Hot Spot – plumes of hot plastic rock that rise from deep in the mantle; volcanic activity is associated with hot spots. Plate convergence in three different settings: Ocean – Ocean subduction Ocean – Continent subduction

6. Continent – Continent subduction Plate Subduction – the denser of the two plates subducts: a) older ocean plate b) always ocean plate Quake occurs as plates slide past one another within the plate at Benioff zone. Volcanic arc – arc-shaped chain of volcanoes on the margin of overriding plate at convergent plate boundary.

8. Island arc – curving series of volcanic islands created by collision of tectonic plates in ocean setting. The particular type of plate boundary that yields island arcs is called subduction zone. Fore-arc basin – located to the “front” of the volcanic arc; forms toward the subducted plate side. Back-arc basin – associated with island arc and subduction zone; found at convergent plate boundaries presently concentrated in Western Pacific Ocean

9. Volcanic arcs in continent (Andes, Cascades) Island arcs in ocean (Aleutians, Philippines) Trenches – deep linear features/depressions that form the surface expression of subduction Mariana Trench – 11+km Philippine Trench – 7+km