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A. B. C. D. Draw and Label the Parts of a Wave. The Ocean Floor. How is the ocean floor studied??. Sonar. SO und NA vigation and R anging Sonar signal sent to ocean floor Time how long it takes to reach bottom and return to surface Side Scan Sonar
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A. B. C. D. Draw and Label the Parts of a Wave
TheOcean Floor How is the ocean floor studied??
Sonar • SOund NAvigation and Ranging • Sonar signal sent to ocean floor • Time how long it takes to reach bottom and return to surface • Side Scan Sonar • Technique that directs sonar waves at an angle
Calculating Depth • D = (1500 m/s) (time / 2) • 1500 m/s = speed of sound in water • Example: • If sound signal takes 4 seconds how far away is the ocean floor at that location? • D = (1500 m/s) (4s/2) • D = (1500 m/s) (2s) • D = 3000 m
Submersibles • Deep Diving Submersible • 2-3 person vessel • Can reach moderate to deep depths • Excellent horizontal movement
Self Contained Diving • 1940s - Developed first practical scuba (aqua lung) • Released compressed air when diver inhaled • Divers could swim freely rather than walk along bottom SCUBA= Self Contained Underwater Breathing Apparatus
Ocean Floor • Continental Margin • Area where the edges of the continents meet the ocean • Shallowest part of ocean • Includes: • Continental Shelf • Continental Slope • Continental Rise
Continental Shelf • Shallowest part of continental margin • Extends into ocean from shore • Average width is 60 km • Depth of water – 130 m
Continental Slope • Quick drop in the seafloor • True edge of continent • Turbidity Currents • Fast moving water currents along sea floor that carve out submarine canyons
Continental Rise • Gently sloping accumulation of sediment at the bottom of the continental slope
Ocean Floor Features • Abyssal Plains • Flattest part of the ocean floor • 5 to 6 km below surface • Seamounts • Underwater basaltic volcanoes • Guyots • Large, extinct, volcanoes with flat submerged tops
Ocean Basins • Mid-ocean Ridge • Underwater chain of mountains • Mid-Atlantic Ridge • Deep Sea Trenches • Deep Elongated Depressions • Marianas Trench
Hydrothermal Vents • At rift zones, water seeps through cracks and gets heated. • Hot water rises dissolving minerals out of rocks as it flows
Hydrothermal Vents • Water emerges from seafloor and comes in contact with cold water • Minerals in hot water form a dark cloud called a Black Smoker
Hydrothermal Vents • Submersibles visited vents more than 2400 meters deep • Temperatures can get as high as 371 Celsius
Case Study • 1977 – Alvin • Parts of seafloor near vents had thick growth of living things • Water very rich in minerals • H2S – Hydrogen Sulfide
Alvin • High Concentration of bacteria • Bacteria uses H2S to make food • Share food with other creatures • Chemosynthesis
Vent Crab Vent Life Pompeii Worm Tubeworms Giant Clam
Life Span of Hydrothermal Vents • Life span varies (months to decades) • Some vents become inactive if there is no Hydrogen Sulfide available • Eruptions can spill out lava killing organisms at vents • New vents die out and appear regularly