Intro to Oceanography CH.2 and 3 Material

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Intro to Oceanography CH.2 and 3 Material
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  1. Bathymetry
    •Measures the vertical distance from the ocean surface to mountains, valleys, plains, and other sea floor features
  2. Measuring Bathymetry
    •Soundings–Poseidonus first sounding 85 B.C.–Line with heavy weight–Sounding lines used for 2000 years

    •Unit of measure is a fathom–1.8 meters (6 feet)

    •First systematic measurements – HMS Challenger 1872
  3. Measuring Bathymetry #2
    •Echo Soundings–Echo sounder or fathometer–Reflection of sound signals–German ship Meteor identified mid-Atlantic ridge in 1925

    •Lacks detail

    •May provide inaccurate view of sea floor
  4. Measuring Bathymetry
    •Precision Depth Recorder (PDR)

    –1950s

    –Focused high frequency sound beam

    –First reliable sea floor maps produced

    –Helped confirm sea floor spreading
  5. Measuring Bathymetry
    Modern Acoustic Instruments

    •Side scan sonar

    –GLORIA (Geological Long-range Inclined Acoustical instrument)

    –Sea MARC (Sea Mapping and Remote Characterization)

    •Can be towed behind ship to provide very detailed bathymetric strip map

    •Multi-beam echo sounder–Seabeam
  6. Sea Floor Mapping From Space
    •Uses satellite measurements.

    •Measures sea floor features based on gravitational bulges in sea surface.

    •Indirectly reveals bathymetry.
  7. Hypsographic Curve
    •Shows relationship between height of land and depth of ocean
  8. Ocean Provinces
    Three Major Provinces

    •Continental margins

    –Shallow-water areas close to shore

    •Deep-ocean basins

    –Deep-water areas farther from land

    •Mid-ocean ridge

    –Submarine mountain range
  9. Continental Margins
    •Passive or Active

    •Passive

    –Not close to any plate boundary

    –No major tectonic activity

    –Example: East coast of United States

    •Active

    –Associated with convergent or transform plate boundaries

    –A lot of tectonic activity
  10. Active Continental Margins
    Convergent or Transform

    •Convergent Active Margin

    –Oceanic-continent convergent plate boundaries

    –Active continental volcanoes

    –Narrow shelf

    –Offshore trench

    –Example: Western South America
  11. Active Continental Margins
    •Transform Continental Margin

    –Less common

    –Transform plate boundaries

    –Linear islands, banks, and deep basins close to shore

    –Example: Coastal California along San Andreas Fault
  12. Continental Margin Features
    •Continental shelf

    •Shelf break

    •Continental slope

    •Continental rise
  13. Continental Shelf
    •Flat zone from shore to shelf break

    –Shelf break is where marked increase in slope angle occurs

    •Geologically part of continent

    •Average width is 70 km (43 miles) but can extend to 1500 km (930 miles)

    •Average depth of shelf break is 135 meters (443 feet)
  14. Continental Shelf
    •The type of continental margin determines the shelf features.

    •Passive margins have wider shelves.

    •California’s transform active margin has a continental borderland.
  15. Continental Slope
    •Where deep ocean basins begin

    •Topography similar to land mountain ranges

    •Greater slope than continental shelf

    –Averages 4° but varies from 1–25° gradient

    •Marked by submarine canyons
  16. Submarine Canyons
    •Narrow, deep, v-shaped in profile.

    •Steep to overhanging walls.

    •Extend to base of continental slope, 3500 meters (11,500 feet) below sea level.

    •Carved by turbidity currents.
  17. Turbidity Currents
    •Underwater avalanches mixed with rocks and other debris.

    •Sediment from continental shelf.

    •Moves under influence of gravity.

    •Sediments deposited at slope base.
  18. Continental Rise
    •Transition between continental crust and oceanic crust

    •Marked by turbidite deposits from turbidity currents.

    •Graded bedding in turbidite deposits

    •Deposits generate deep

    -sea fans, or submarine fans.

    •Distal ends of submarine fans becomes flat abyssal plains.
  19. Abyssal Plains
    •Extend from base of continental rise.

    •Some of the deepest, flattest parts of Earth.

    •Suspension settling of very fine particles.

    •Sediments cover ocean crust irregularities.

    •Well-developed in Atlantic and Indian oceans.
  20. Abyssal Plain Volcanic Peaks
    •Poke through sediment cover

    •Below sea level:

    –Seamounts, tablemounts, or guyots at least 1 km (0.6 mile) above sea floor

    –Abyssal hills or seaknolls are less than 1 km (0.6 mile) above sea floor•Above sea level:

    –Volcanic islands
  21. Ocean Trenches and Volcanic Arcs
    •Convergent margins generate ocean trenches.–Deepest part of oceans.

    –Most in Pacific Ocean.–Deepest trench

    – Mariana Trench at 11,022 meters (36,161 feet).

    •Volcanic arc on nonsubducted ocean plate.–May produce island arc, e.g., Japan.

    •Continental arc on land.
  22. Pacific Ring of Fire
    •Margins of Pacific Ocean.

    •Majority of world’s active volcanoes and earthquakes.

    •Marked by convergent boundaries.
  23. Mid-Ocean Ridge
    •Longest mountain chain.

    •On average, 2.5 km (1.5 miles) above surrounding sea floor.

    •Wholly volcanic.

    •Basaltic lava.

    •Divergent plate boundary.
  24. 12Mid-Ocean Ridge Features
    •Central rift valley downdropped by seafloor spreading

    –Fissures and faults in rift valley

    •Seamounts

    – tall volcanoes

    •Pillow lava or pillow basalt

    – shapes formed when hot basaltic lava quickly cools.
  25. Mid-ocean Ridge Features
    Hydrothermal Vents

    •Sea floor hot springs.

    •Foster unusual deep

    -ocean ecosystems able to survive without sunlight.

    •Warm water vents

    – temperatures below 30°C (86°F).

    •White smokers

    – temperatures from 30

    –350°C (86–662°F).

    •Black smokers

    – temperatures above 350°C (662°F).
  26. Oceanic Divisions
    •Ocean can be divided in to two main environments:

    –Pelagic

    •The ocean water itself with plankton and nekton.

    –Benthic

    •The ocean bottom with epifauna and infauna.
  27. Pelagic Environment
    •Divided further into distinct life zones called biozones.

    –Each biozone possess unique physical characteristics.

    •Neritic province

    –Near shore (all water less than 200 m).

    •Oceanic province

    –The rest of the ocean.
  28. Biozones
    •Oceanic province divided into four biozones:

    –Epipelagic

    •Surface to 200 m

    –Mesopelagic

    •200

    – 1000 m

    –Bathypelagic

    •1000

    – 4000 m

    –Abyssopelagic

    •Greater than 4000 m
  29. Light
    •Most important factor determining distribution of life in the ocean.

    •Zonation based on light:

    –Euphotic zone

    •Enough light to support photosynthesis ~100m.

    –Disphotic zone

    •Small amount of light extends down to 1000 m.

    –Aphotic zone

    •No light reaches these areas below 1000 m.
  30. Epipelagic Zone
    •Only place where photosynthesis can occur in the ocean.

    •Dissolved oxygen begins to decrease significantly at the bottom of this zone.

    –Why?

    •Nutrients being increasing below 200 m.

    –Why?
  31. Mesopelagic Zone
    •Oxygen Minimum Layer occurs at ~ 700

    – 1000 m.

    •Most nutrient laden waters in the ocean occur at these depths.

    •Bioluminescent organisms prevalent in this zone.

    –Why?
  32. Aphotic Zones
    •Bathypelagic and abyssopelagic zones make up 75% of the oceanic province.

    •Small and large unusual looking orgnaisms live here.

    –Some completely blind.

    –Adapt to feeding habits

    •Oxygen increases at these depths?

    –Why?
  33. Benthic Environments
    •Supralittoral zone

    –Transitional region from land to seafloor.

    –“Spray Zone”

    •Subneritic Province

    –Benthic zone spreading to a depth of 200m.

    •Suboceanic Province

    –Benthic zone deeper than 200m
  34. Subneritic Province
    •Divided further based on tides.

    •Littoral zone

    –Intertidal zone

    –The zone between high and low tides.

    •Sublittoral zone

    –Extends from lowtide out to a depth of 200m

    •Inner sublittoral ~50 m

    •Outter sublittoral 50 – 200 m
  35. Suboceanic Province
    •Divided in to three zones

    –Bathyl zone

    –Abyssal zone

    –Hadal zone
  36. Bathyl Zone
    •Bathyl zone

    –Extends from 200 m

    – 4000m

    –Follows the continental slope.
  37. Abyssal zone
    •Abyssal zone

    –4000

    – 6000 m–80% of benthic environment–Soft oceanic sediment (clay)
  38. Hadal Zone
    •Hadal zone

    –Below 6000 m

    –Found in the Deep trenches

    –Communities are generally isolated from each other resulting in unique adaptations.
  39. Dirt and Goo?
    •What are sediments?

    –Eroded rock particles and fragments

    •Transported to ocean

    •Deposit by settling through water column

    •Oceanographers decipher Earth history through studying sediments.
  40. Marine Sediments
    •Over time sediments become lithified and form sedimentary rock.

    –More than half the rock exposed on continents are sedimentary rock.

    •Most tall mountains contain marine fossils.

    –Gives evidence of seafloor spreading.
  41. Paleoceanography
    •As sediment falls to the floor, it preserves what it covers.

    •Gives a look in to previous oceanographic condition.

    –SST–Nutrients

    –Marine Life

    –Currents, etc..
  42. Paleoceanography #2
    •Recent paleooeanography research has found linked changes in deep

    -ocean circulation and rapid climate change.

    •Have found evidence of abrupt changes in climate in N. Atlantic due to fluctuations of freshwater from melting glaciers.
  43. Sediment Collection
    •Can be extremely difficult.

    •Early expeditions used a dredge to scoop up sediment for analysis.

    –Only good for sediment on ocean floor.

    •Gravity Corer

    –Steel tube with heavy weight on top.

    •Rotary Drilling

    –Collects cores from deep ocean.
  44. Lithogenous Sediment
    •Lithogenous Sediment.

    –Sediment derived from pre-existing rock material.

    –Produced by weathering.

    •Breaking of rocks into smaller pieces.

    –Originates on the continents or islands from erosion, volcanic eruptions, or blown dust.
  45. Lithogenous Sediment
    •Small particles eroded and transported.

    •Carried to ocean.

    –Streams

    –Wind

    –Glaciers

    –Gravity

    •Greatest quantity around continental margins.
  46. Lithogenous Sediment
    •Composition

    –Reflect rock from which derived.

    –Coarser sediments closer to shore.

    –Finer sediments farther from shore.

    –Mainly mineral quartz (SiO2).
  47. Lithogenous Quartz
    •Large percentage of lithogenous quartz are transported from deserts by prevailing winds.
  48. Lithogenous Sediment Texture
    •Grain size is classified using Wentworth scale of grain size.

    •Sediment size is proportional to energy of transportation and deposition.
  49. Lithogenous Sediment Texture #2

    •Sorting plays role in the texture of lithogenous sediment.

    –Measure of the uniformity of grain sizes.

    –Indicates selectivity of transportation process.

    •Well sorted areas show same sized particles.

    –Sand dunes.

    •Poorly sorted particles show many different sizes.

    –Glacier picking up boulders and clay and moving them around.
  50. Lithogenous Sediment Texture
    •Textural maturity can be determined based on:

    –Clay content.

    •Decreases with maturity.

    –Sorting increases.

    –Non

    -quartz minerals decrease.

    –Grains are more rounded.
  51. Distribution
    •Marine sediment broken in to two catagories:

    •Neritic

    –Shallow water–Close to shore

    –Deposit quickly

    •Pelagic

    –Deeper water

    –Fine grained

    –Deposit slowly
  52. Neritic Deposits
    •Dominated by lithogenous sediment.

    –Derived from nearby landmasses.

    •Four types:

    –Beach deposits.

    •Wave controlled (quartz rich).

    –Continental shelf deposits.

    •Old river deposits (sea level fall).

    –Turbidite deposits.•Turbidity currents.–

    Glacial deposits.
  53. Pelagic Deposits
    •Turbidite deposits do spill over in to deep

    -ocean basin.

    –Not primary source of sediment.

    •Fine-grained material.

    •Accumulates slowly on deep ocean floor.

    •Pelagic lithogenous sediment from.

    –Volcanic ash (volcanic eruptions).

    –Wind

    -blown dust.

    –Fine-grained material transported by deep ocean currents.
  54. Pelagic Deposits
    •Abyssal Clay

    –70% clay sized particles derived from continents.

    –Transported by wind/currents.

    –Generally red in color•Fe–Abundant because of lack of other sediments.
  55. Biogenous Sediment
    •Hard remains of once

    -living organisms.

    –Diatoms, Cocolithophores, etc…

    •Two major types:

    –Macroscopic

    •Shells, Bones, Teeth.

    –Microscopic

    •Shells, tests.

    •Biogenic ooze.

    •Mostly algae and protozoans.
  56. Biogenous Sediment #2

    •Composed of two main chemical compounds.

    –Calcium Carbonate (CaCO3).

    –Silica (Si02).
  57. Silica Based Critters
    •Two primary groups of animals with silica tests.

    –Diatoms

    •Photosynthetic

    •Planktonic

    •Small holes to allow for nutrient passage.

    •Diatomaceous earth.
  58. Silica Based Critters
    •Two primary groups of animals with silica tests:

    –Radiolarians

    •Microscopic single

    -celled protozoans.

    •Most Planktonic

    •Heterotrophic

    •Well developed symmetry.
  59. Calcium Carbonate Critters
    •Two different groups:

    –Coccolithophores

    •Also called nannoplankton.

    •Photosynthetic algae.

    •Coccoliths

    – individual plates from dead organism.•Rock chalk

    •Lithified coccolith

    -rich ooze.
  60. Calcium Carbonate Critters
    •Two different groups:

    Foraminiferia

    •Protozoans

    •Heterotrophic

    •Planktonic

    •Make up calcareous ooze.
  61. Distribution of Biogenous Sediment
    •Most common form of pelagic deposit.

    •Distribution and abundance is dependent on three processes:

    –Productivity

    –Destruction

    –Dilution
  62. Distribution of Biogenous Sediments
    •Productivity

    –Varies globally

    –Based on the number of organisms present in the surface water.

    –High productivity = high biogenous sediment.

    –Low productivity = low biogenous sediment.
  63. Distribute of Biogenous Sediment
    •Destruction:

    –The dissolution of skeletal remains.

    –Can happen prior to ever reaching sea floor.

    –Can also occur prior to accumulation on sea floor.
  64. Distribution of Biogenous Sediments
    •Dilution:

    –Deposition of other sediments decreases percentage of biogenous sediments.

    –Increased occurance of lithogenous sediment.

    •Volcano

    •Hurricane
  65. Neritic Deposits
    •Dominated by lithogenous sediment, may contain biogenous sediment.

    •Carbonate Deposits.

    –Carbonate minerals containing CO3.

    –Marine carbonates primarily limestone

    – CaCO3 .

    –Most limestones contain fossil shells.

    •Suggests biogenous origin.

    –Ancient marine carbonates constitute 25% of all sedimentary rocks on Earth.
  66. Carbonate Deposits
    •Stromatolites

    –Fine layers of carbonate.

    –Warm, shallow-ocean, high salinity.

    –Cyanobacteria
  67. Pelagic Deposits
    •Bigenous sediment is most common due to distance from land.

    –Decreases likely-hood of particle transportation.

    •Siliceious Ooze–Contains at least 30% of hard remains.

    •Diatomacrous vs radiolarian.

    –Ocean lacking in silica

    •Leads to quick dissolution.
  68. Pelagic Deposits
    •Calcareous Ooze and the CCD

    –Calcareous Ooze: at least 30% calcareous organisms.

    –CCD: Calcite compensation depth

    •Depth where CaCO3 readily dissolves.
  69. Calcareous Ooze and the CCD
    •Warm, shallow ocean saturated with calcium carbonate.

    •Cool, deep ocean undersaturated with calcium carbonate.

    –Lysocline


    – depth at which a significant amount of CaCO3 begins to dissolve rapidly.

    •Scarce calcareous ooze below 5000 meters (16,400 feet) in modern ocean.

    •Ancient calcareous oozes at greater depths if moved by sea floor spreading.
  70. Hydrogenous Marine Sediments
    •Minerals precipitate directly from seawater.

    •Occurs when there is a change in conditions.

    –Temperature

    –Pressure

    –Added Chemicals
  71. Hydrogenous Marine Sediments
    •Four primary forms of hydrogenous marine sediment:

    –Manganese nodules

    –Phosphates

    –Carbonates

    –Metal sulfides

    •Small proportion of marine sediments.

    •Distributed in diverse environments.
  72. Manganese Nodules
    •Fist-sized lumps of manganese, iron, and other metals.

    •Very slow accumulation rates.

    •Many commercial uses.

    •Unsure why they are not buried by seafloor sediments.
  73. Phosphates and Carbonates
    •Phosphates

    –Phosphorus

    -bearing.

    –Occur beneath areas in surface ocean of very high biological productivity.

    –Economically useful as fertilizer.

    •Carbonates

    –Aragonite and calcite.

    –Oolites
  74. Metal Sulfides
    •Metal sulfides

    Contain:

    •Iron

    •Nickel

    •Copper

    •Zinc

    •Silver

    •Other metals

    –Associated with hydrothermal vents.
  75. Evaporates
    •Evaporates

    –Minerals that form when seawater evaporates.

    –Restricted to the open ocean or areas with high evaporation rates.

    –Halite (common table salt) and gypsum.
  76. Cosmogenous Marine Sediments
    •Macroscopic meteor debris.

    •Microscopic iron-nickel and silicate spherules (small globular masses).

    –Tektites

    –Space dust

    •Overall, insignificant proportion of marine sediments.
  77. Marine Sediment Mixing
    •Pure deposits of lithogenous and biogenous sediment are rare.

    –Usually mixture of different types.

    –Dominate different areas on the sea floor.
  78. Sediment Distribution
    •Neritic sediments cover about ¼ of the sea floor.

    •Pelagic sediments cover about ¾ of the sea floor.
  79. Sediment Distribution
    •Distribution controlled by

    –Proximity to sources of lithogenous sediments.

    –Productivity of microscopic marine organisms.

    –Depth of water.

    –Sea floor features.
  80. Sea Floor Sediments Represent Surface Ocean Conditions
    •Microscopic tests sink slowly from surface ocean to sea floor (10-50 years).

    •Tests could be moved horizontally.

    •Most biogenous tests clump together in fecal pellets.

    –Fecal pellets large enough to sink quickly (10-15 days).
  81. Resources from Marine Sediments
    •Filters

    •Mild Abrasives

    –Toothpaste /Facial Scrubs

    •Absorbents

    –Chemical Spills/Pest Control

    •Chemical Carriers–Pharmaceuticals, Paint, and Dynamite
  82. Resources from Marine Sediments
    •Optical quality glass

    •Space shuttle tiles

    •Concrete additives

    •Filler in tires

    •Stone for houses
  83. Fossil Fuels
    •Three major types:

    –Coal

    –Natural Gas

    –Oil

    •Formed primarily by plant based life several hundred million years ago.

    •Diatoms greatest portion of fossil fuels.

    –How do we know?
  84. Fossil Fuel Formation
    •Organisms (plant and animal) eventually die and fall to the sea floor.

    •Low oxygen environment

    –Keeps organic material from breaking down.
  85. Fossil Fuel Formation
    •This dead organic matter is covered with silt and mud.

    •Silt/mud compresses down and becomes rock.

    •The rock leaves the organic matter trapped between two layers of rock.
  86. Fossil Fuel Formation
    •Over millions of years more silt and mud is laid down, adding additional layers of rock.

    •The weight of the rock and heat from the earth removes water out of the organic material.
  87. Fossil Fuel Formation
    •The organic matter is now liquid oil or gas.

    –Why large amounts in small areas?

    •Porous vs Non-porous rocks.

    –Liquid oil and gas seeps through porous rocks because of surrounding pressure.

    –Moves until it reaches a non

    -porous layer where it remains.
  88. Fossil Fuel Locations
    • Why here?

    – 250

    -35 MYA

    – GOM was a giant tidal flat

    – Swampy wetlands created algalmats

    • Nutrient rich areas

    – Over 8000 oil and gas seepsin GOM
  89. Resources from Marine Sediments
    • Sand and gravel (includingtin, gold, and so on)

    • Evaporative salts

    • Phosphorite

    • Manganese nodules andcrusts

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