Earth Sciences 1022A/B Lecture Notes - Lecture 11: Abyssal Plain, Subduction, Graded Bedding
19 Oct 2016
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Passive: no volcanoes, few earthquakes; 3 parts (diagram in notes: continental shelf gentle gradient to ~130m depth, continental slope steeper slope beyond the shelf, continental rise gentle slope under deep-sea fan sediments. Submarine canyons: valleys carved by rivers into the continental slope during lower sea level or by turbidity currents, turbidity currents deposit turbidites with graded bedding (course > ne) Active: at subduction zones with deep-ocean trenches and accretionary wedges. Reef: skeletal remains of corals that grow in warm sunlit sea water up to 45m deep. Atoll: ring-shaped reef around a submerged volcano. Submarine ridge system with wide rift valleys that are offset by transform faults. Fresh sea oor cools and contracts as it moves toward abyssal plain.
