Earth Sciences 1022A/B Lecture 11: Earth Science Lecture February 23 2016

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

Document Summary

Mapping the ocean floor is done by comparing multibeam sonar and satellite. Passive continental margins: not associated with plate boundaries volcanoes or earthquakes. Gentle slope from shoreline to a depth of about 130 m: about 80 km wide. Useful for oil and gas reserves, fishing, and sand and gravel deposits. Steeper slope beyond the shelf about 20 km wide that forms the boundary between continental crust and oceanic crust. Gentle slope formed by turbidity currents and deep-sea fans. Valleys cut into the continental slope: some extend from river valleys carved during glaciations. Others form by earthquake induced turbidity currents of dense sediment-rich water eroding the shelf and slope. Turbidity currents form turbidites with graded bedding: coarse particles on bottom. Active continental margins: where oceanic lithosphere is subducted under continental lithosphere. The edge of deep ocean trench is the continental lithosphere. About 30% of the earth"s surface: similar to the total area of land.