ES Chapter 14

1
ES Chapter 14

• The Ocean Floor

2

• Earths Oceans
• Nearly 71 percent of Earths surface is covered
  by the global ocean
• We know very little about the ocean.
• The oceans began to be explored in the late
  1800s.
• Oceanography is a science that draws on the
  methods and knowledge of geology, chemistry,
  physics and biology to study all aspects of the
  world ocean.

3

• Geography.
• The world ocean can be divided into four main
  ocean basins.

4

• Pacific Ocean largest ocean
• Largest single geographic feature on earth
• Worlds deepest ocean
• Atlantic Ocean about half the size of the
  Pacific Ocean
• About half as deep as the Pacific
• Relatively narrow compared to the Pacific.

5

• Indian ocean slightly smaller than the Atlantic
• About the same average depth as the Atlantic
• Located almost entirely in the Southern
  hemisphere.
• Arctic Ocean - 7 the size of the Pacific.
• A little more than one quarter as deep as the
  rest of the oceans.

6

• Mapping the Ocean floor
• Sonar is a type of electronic depth sounding
  equipment.
• Sonar is an acronym sound navigational and
  ranging.
• It works by transferring sound waves to the ocean
  bottom.

7
(No Transcript)
8
(No Transcript)
9

• A receiver intercepts the echo reflected from the
  bottom
• Using a clock, the echo reflected from the bottom
  can be used to calculate depth of the water.
• The ocean floor is mapped in strips as a ship
  moves back and forth scanning with sonar.

10

• Satellites measure the shape of the ocean
  surface from space.
• The ocean surface is not perfectly flat
• Gravity attracts water toward region where
  massive ocean floor feature occur.
• Mountains and ridges produce elevated areas on
  the ocean surface
• Trenches produce slight depressions.
• Satellites can tell a great deal about the ocean
  floor topography by bouncing microwaves off the
  ocean surface.

11
(No Transcript)
12

• Submersibles used to collect data about areas
  of the ocean that were previously unreachable by
  humans
• Video and photos record previously unknown
  creatures that live in the abyss.
• Unmanned submersibles are operated by remote
  sensors.

This one goes to 750 m.
13
Submersibles.

• This is Alvin. It goes to a depth of a few
  thousand m.
• On 27 January 1960 the Trieste took two men to a
  depth of 35,800 ft ft (10,910 meters) -- the
  deepest spot in the ocean -- in the Mariana
  Trench near Guam. It took 5 hours to fall 7
  miles, and when the explorers reached the bottom
  they stayed 20 minutes. No one has been able to
  come near that depth since then. At this depth,
  the pressure is over 8 tons per square inch. In
  1963, she went to the Atlantic to search for the
  lost submarine USS Thresher (SSN-593). In August
  1963, Trieste found Thresher's remains off New
  England, 1400 fathoms below the surface. The
  bathyscaphe was retired soon after that, and some
  of her components were used in the newly
  constructed Trieste II. Trieste is currently on
  display at the Washington Navy Yard museum.

14

• Ocean floor
• Continental margins this is the transition area
  between a continent an the adjacent ocean basin
  floor.
• In the Atlantic, there are thick layers of
  undisturbed sediment
• Very little volcanic or earthquake activity

15

• In the Pacific, the oceanic crust is plunging
  beneath continental crust.
• Continental shelf gently sloping submerged
  surface extending from the shoreline. It may be
  almost non-existent or may be as wide as 1500 km.
  They contain important mineral deposits and have
  large reservoirs of oil and natural gas and huge
  sand and gravel deposits.

16

• Continental Slope
• The slope is steeper than the shelf. Not as wide
  as the shelf. Submarine canyons cut into the
  continental slope
• Eroded in part by turbidity currents.
• Turbidity currents are movements of dense,
  sediment-rich water down the continental slope.
• As this material flows down, it erodes and
  accumulates more sediment.
• Turbidity currents are known to be an important
  mechanism of sediment transport in the ocean.

17
Submarine Canyons
18

• Continental rise a more gradual incline in
  regions where there is no trench associated off
  the coast of a continent

19

• Ocean basin floor
• Deep Ocean Trenches these are long narrow
  creases in the ocean floor. This is where the
  deepest parts of the ocean are.
• There are many located along the margins of the
  Pacific.
• The Mariana Trench is 11,002 m deep.
• Trenches form at sites of plate convergence,

20

• Abyssal Plains these are deep and extremely
  flat.
• They are covered with thick accumulations of fine
  sediment.
• The sediments are deposited there by turbidity
  currents.

21

• Seamount a submerged volcano
• They havent reached the surface yet.
• Some seamounts occur at hot spots.
• Once the volcano reaches the ocean surface it
  becomes an island
• Erosion wears away the island.
• If it is not as active and is below sea level and
  flat. It is called a guyot.

22
(No Transcript)
23

• Mid-ocean ridge
• Found near the center of most ocean basins.
• Longest topographic feature on Earths surface.
• Exceeds 70,000 km in length.
• They are not narrow
• Widths from 1000 to 4000 km and may occupy as
  much as one half of the total area of the ocean
  floor.

24

• It is broken into segments and are offset by
  large transform faults.
• Volcanic activity along the ridge is associated
  with seafloor spreading.
• New ocean floor is formed at mid-ocean ridges as
  magma rises between the diverging plates and
  cools.
• Hydrothermal vents form alongside mid-ocean
  ridges.
• Mineral rich water containing metals such as
  sulfur, iron, copper and zinc.

25

• It is broken into segments and are offset by
  large transform faults.
• Volcanic activity along the ridge is associated
  with seafloor spreading.
• New ocean floor is formed at mid-ocean ridges as
  magma rises between the diverging plates and
  cools.
• Hydrothermal vents form alongside mid-ocean
  ridges.
• Mineral rich water containing metals such as
  sulfur, iron, copper and zinc.

26

• Seafloor sediments
• Most of the ocean floor is covered with sediment.
• Some has been deposited as turbidity currents
• Some accumulates from the surface.
• The accumulation may be close to 10 km.

27
Type of sediment , Description

• Terrigenous Sediment - Mineral grains that were
  eroded from continental rocks and transported to
  the ocean.
• Biogenous Sediment - Biological in origin,
  consists of shells and skeletons of marine
  animals and algae. The most common is calcareous
  ooze which is found in the shallower areas of
  ocean basins. Siliceous ooze consists
  primarily of diatoms.

28

• Hydrogenous Sediment - Consists of minerals that
  crystallize directly from the ocean water through
  various chemical reactions. There are many kinds
  with different combinations. Manganese nodules,
  calcium carbonate and evaporates such as halite.

29

• Energy Resources
• Oil and natural gas are the ancient remains of
  microscopic organisms. They were buried with
  marine sediments before they could decompose.
• Gas hydrated compact chemical structures made
  of water and natural gas.

30

• They occur beneath permafrost areas on land and
  under the ocean floor ad depths blow 525 m.
• Created when bacteria break down organic matter
  trapped in ocean-floor sediments.
• They are able to burn like fuel.
• They are present in quantities that are more than
  the worlds coal, oil and natural gas combined.

31

• Sand and Gravel are used for landfill
• Some gem quality diamonds have been found
  offshore of South Africa and Australia.
• Manganese nodules contain high concentrations of
  manganese, iron and smaller concentrations of
  copper, nickel and cobalt.
• Evaporative salts in areas where seawater
  evaprorates, salt can be harvested.