Earth Sciences 1022A/B Lecture 13: Earth Science Lecture March 1 2016

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 1022A/B
• Professor: Stephen R Hicock

Document Summary

Continents rise above oceans due to isostasy: buoyant continental lithosphere floats on dense asthenosphere. Thicker lithosphere creates higher mountains with deeper roots. Mountain building processes are collectively called oogenesis. Mountain (orogenic) belts parallel plate boundaries in three main settings of continental margins. Divergent: mantle plumes, rises, uplifts and splits continental lithosphere to form rift valley with blocks dropped along normal faults and volcanoes along valley sides. Passive: rift widens, sea water invades and a new ocean basin forms whose sides experience no seismic activity but gradually subside under the weight of sediment load. Convergent: as mountains grown, they undergo isostatic adjustments, andean-type. Develops accretionary wedge, continental volcanic arc and plutons in the core of deformed mountain belts: aleutian-type. Oceanic crust subducts under oceanic crust to form volcanic island arc: continental collision. This leads to the highest mountains forming: accreted terranes. Foreign pieces of crust forcefully attached to continental margin. Wilson cycle: oceans opened and closed, mountains built and rebuilt repeatedly.