The Ocean Basins

1. The Ocean Basins Earth Science Spring 2013

2. The Water Planet • Global ocean covers 97% of the earth’s surface. • Global ocean divided into 3 major oceans: • Atlantic • Pacific • Indian • Sea- small areas of ocean that are partially surrounded by land • Ex: Mediterranean, Caribbean, & Coral

3. The Water Planet • Each ocean has special characteristics • Arctic Ocean (northern part of the Atlantic)- water near the surface is less salty than water in the other oceans • Pacific Ocean- largest feature on Earth’s surface • Deepest ocean • Sea of Japan, Bering, Coral, and South China seas are all parts of the Pacific Ocean • Atlantic Ocean- 2nd largest ocean • Mediterranean, Caribbean, and Baltic seas & Gulf of Mexico are all parts of the Atlantic Ocean • Indian Ocean- 3rd largest ocean • Arabian & Red Seas are part of the Indian Ocean

4. Exploration of the Ocean • Oceanography- study of the physical characteristics, chemical composition, & life forms of the ocean • 1872- 1876: H.M.S Challenger laid the foundation for modern oceanography • Today there are many ships equipped to perform oceanographic research • Ex: JOIDES Resolution • Ocean floor- made up of continental & oceanic crust that lie beneath the ocean waters

5. Exploration of the Ocean • Submersibles • Underwater research vehicles • Some are piloted by people • More advanced ones are robotic • Photograph & collect samples from the ocean floor • Several types have been used • Bathysphere- spherical vessel that was first used for deep-ocean exploration (manned) • Bathyscaph- self propelled, free-moving submarine equipped for deep-ocean research (manned) • Robot submersibles- allow exploration of great depths & for long periods of time

6. Exploration of the Ocean • Sonar • Sound Navigation and Ranging • Consists of a transmitter & a receiver • Transmitter- sends out a continuous series of sound waves from the ship to the ocean floor • Receiver- sound waves hit the ocean floor & reflect back up to the receiver • Amount of time it takes the waves to go round trip determines the depth

7. Features of the Ocean Floor • 2 major divisions of ocean floor • Continental margins • Shallower portions of the ocean floor • Made up of continental crust & a thick sediment wedge • Deep ocean basin • Deeper portion of the ocean • Made up of oceanic crust & a thin sediment layer

8. Features of the Ocean Floor: Continental Margins • Continental Shelf • Edge of a continent covered by shallow ocean water • Usually slopes gently • Average depth of water 60 meters • Part of the continental margin • Affected by changes in sea level

9. Features of the Ocean Floor: Continental Slope • Continental Slope • Steep incline at the edge of the continental shelf • Boundary between continental & oceanic crust is at the base of the continental slope • Ocean depth increases to thousands of meters • Continental shelf & continental slope maybe cut by deep v-shaped valleys • Submarine canyons • Often associated with the mouths of major rivers • Turbidity currents- dense current that carries large amounts of sediment down the continental slopes • Continental rise- accumulation of sediments at the base of the continental slope

10. Features of the Ocean Floor: Deep Ocean Basins • Trenches • Deep valleys in the ocean floor • Ex: Mariana Trench- deepest place in the world, estimated to be 11,000m deep • Most are located along the Pacific Ring of Fire • Associated with earthquakes, volcanic mountain ranges, volcanic island arcs

11. Features of the Ocean Floor: Deep Ocean Basins • Abyssal Plains • Extremely flat areas that lie deep beneath the ocean • Cover about half of the deep-ocean basin • Flattest regions on earth • Made up of deposited sediments

12. Features of the Ocean Floor: Deep Ocean Basins • Mid-Ocean Ridges • Continuous series of underwater mountain ranges that run along the floors of all the oceans • Form when plates pull away from each other • Rift along the crest • New crust is formed here • Fracture zones – series of faults forms due to the different rates at which the mid-ocean ridge separates

13. Features of the Ocean Floor: Deep Ocean Basins • Seamounts • Submerged volcanic mountains at least 1000m tall • Generally associated with hot spots • Hawaii & Canary Islands are seamounts that have risen above the ocean surface • Guyots (GEE-oze) – flat-topped, submerged seamount • Cause by erosion and the sinking of ocean crust

14. Ocean-Floor Sediments • Sediments closer to shore are generally coarser than those found in the deep-ocean basins • Sediments come from 2 things: • Washed into the ocean by rivers • Wave erosion of the shoreline • Core samples- cylindrical sample of sediments from the deep-ocean floor

15. Ocean-Floor Sediments: Sources • Inorganic Sediments • Rock particles carried by rivers • Volcanic dust that has been blown far out to sea by the wind • Icebergs carry large amounts of sediments which are deposited as they melt • Cosmic dust from meteorites that have been vaporized in the atmosphere

16. Ocean-Floor Sediments: Sources • Organic Sediments • Remains of marine plants and animals • 2 common substances in organic sediments • Silica (SiO2) • Calcium Carbonate (CaCO3)

17. Ocean-Floor Sediments: Sources • Chemical Deposits • Materials that are formed during chemical reactions that take place in the ocean. • Nodules of minerals form on abyssal plains • Composed mainly of oxides of manganese, nickel, and iron

18. Ocean-Floor Sediments: Physical Classification • 2 general types of sediments found on the ocean floor • Muds- very fine silt and clay sized particles of rock that have settled to the ocean floor • Ooze- soft organic sediment on the ocean floor • At least 30% organic materials & rest is made up of fine mud • 2 types of ooze • Calcareous ooze- mostly calcium carbonate • Siliceous ooze- mostly carbon dioxide