The Ocean Floor Chapter 14 pg 393

71% of earth is covered by ocean Oceanography – study of the ocean A. The Vast World Ocean The blue planet 71% of earth is covered by ocean Oceanography – study of the ocean Geography of oceans 4 main ocean basins Pacific Ocean Largest ocean Deepest ocean (average depth 2.45 miles)

2) Atlantic a) Half the size as Pacific and not as deep b) East coast of USA 3) Indian Ocean a) Smaller than Atlantic b) Same average depth as Atlantic c) Sothern hemisphere

4) Arctic Ocean a) 7% the size of Pacific b) 25% as deep as other oceans b. 5th ocean 1) Southern/Antarctic ocean 2) Historically not included c. 1 global ocean

3. Mapping the Ocean Floor a 3. Mapping the Ocean Floor a. Topography – detailed mapping of areas features b. Will find – mountain ranges, trenches, plateaus, and volcanoes c. HMS Challenger – lowered long weighted cables

d. Today 1) SONAR a) Sound Navigation And Ranging b) Bounces sound waves off ocean floor c) Records time it takes to return Multiple beam sonar – more than one sound source

2) Satellites 3) Submersibles a) Small underwater craft used for deep sea research b) Varying technology: cameras, thermometers, pressure gauges, mechanical arms, etc. c) Can be manned or unmanned

B. Ocean floor features Continental Margins Transition zone b/w continents and the adjacent ocean floor Continental Shelf Gentle sloping surface extending from the shoreline Contain important features Mineral deposits Oil and natural gas Sand and gravel deposits

c. Continental Slope 1) Marks the boundary b/w continental and oceanic crust 2) Submarine canyons a) Deep, steep-sided valleys b) Made by turbidity currents – movements of dense, sediment-rich water down the continental slope

d. Continental Rise – continental slope merges into a more gradual incline

2. Ocean basin floor a. Area between continental margin and mid-ocean ridge b. Deep-Ocean Trenches 1) Long, narrow creases in ocean floor 2) Cause deepest parts of ocean 3) Mariana Trench a) Deepest known place on earth b) 11,022 meters (6.8 miles)

4) Occur at subduction zones 5) Have earthquakes and volcanoes

Mariana Trench Deepest Place In The World

Animals of the Mariana Trench

c. Abyssal plains 1) Deep and extremely flat features 2) Sediments burry all other features by turbidity currents d. Seamounts – submerged volcanic peaks

3. Mid-ocean ridges a. Near center of most ocean basins b 3. Mid-ocean ridges a. Near center of most ocean basins b. Longest topographical feature on earth c. Seafloor spreading 1) Happens at divergent plate boundaries 2) Forms new ocean floor with rising magma d. Hydrothermal vents 1) Causes mineral-rich, heated water 2) Hits cold water and S, Fe, Cu, and Zn precipitate out

Hydrothermal Vents Tube Worms

C. Seafloor sediments Terrigenous – sediments originating from land Biogenous – sediments with a biological origin Calcareous ooze – produced from calcium carbonate in shells Siliceous ooze – produced from diatoms Hydrogenous – minerals that crystallize directly from ocean water by chemical reactions

D. Resources from the seafloor Energy Resources Oil and natural gas Main energy source from ocean floor Remains of animal remains Concerns with oil spills

2010 Bp oil spill

b. Gas Hydrates 1) Compact chemical structures 2) Typically form when bacteria break down organic material

2. Other Resources a. Sand and Gravel 1) 2nd in economic value to petroleum industry 2) Used for landfills and concrete 3) Some places contain titanium, gold, or diamond deposits

b. Manganese Nodules 1) Lumps of manganese and other metals 2) Fairly wide spread 3) Environmental concerns with mining

c. Evaporative salts 1) Salt precipitates out of water 2) Gives halite (table salt) 3) Used for seasoning, preserving, agriculture, and clothing industry