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Lecture_09 - LECTURE 9 Ocean Dynamics 1.0 Character of Sea...

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LECTURE 9 - Ocean Dynamics 1.0 Character of Sea Floor Oceanic ridges Detailed mapping of Atlantic seafloor during cold war revealed great ridge 65,000 km long and 1500 km wide with central valley ( rift valley ) 1-3 km deep. Built of basalt. Similar interconnected mid-ocean ridges found elsewhere. Ridge comes to surface at Iceland, Azores, and Galapagos islands. Largest topographic feature on Earth. Transform faults - Occur approximately every 100 km along ridge axes and characterized by escarpments, some >1000 km long. Hydrothermal vents- Hot (350ºC) sulfur-rich solutions rising from volcanic rocks within central valleys. Form meter-high dark mounds ( black smokers ) composed of metal–rich precipitates. Abyssal plains 5-6 km deep, incredibly flat, and underlain by blanket of fine sediment (mud) up to 5 km thick that blankets the oceanic crust ; thins towards mid-oceanic ridges. Forms most of ocean floor. Seamounts- undersea mountains (usually of volcanic origin) on the abyssal plain rising above 1000 from the seafloor and peaking below sea level. Most common in the Pacific Ocean. Submerged, often flat-topped, seamounts called guyots . Passive continental margins Continental shelves – Flat surfaces along most continental margins, underlain by shallow-water sediment several km thick and continental crust . May extend seaward as much as
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