A. D. C. B. Draw and Label the Parts of a Wave

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 H 2 S – Hydrogen Sulfide

Alvin High Concentration of bacteria Bacteria uses H 2 S to make food Share food with other creatures Chemosynthesis

Vent Life Giant Clam Tubeworms Vent Crab Pompeii Worm

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