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Marine Provinces. Bathymetry. Bathymetry is the measurement of ocean depths and the charting of the shape or topography of the ocean floor The ocean floor is a highly varied terrain that contains many interesting features Early methods used a long weighted line (called a sounding line). - PowerPoint PPT Presentation

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Page 1: Marine Provinces
Page 2: Marine Provinces

Bathymetry

• Bathymetry is the measurement of ocean depths and the charting of the shape or topography of the ocean floor

• The ocean floor is a highly varied terrain that contains many interesting features

• Early methods used a long weighted line (called a sounding line)

Page 3: Marine Provinces

Bathymetric techniques

• Echosounders send sound through water to determine water depth and sea floor features

Page 4: Marine Provinces

Bathymetric techniques

• Side-scan sonar uses a “fish” towed behind a ship to give a more detailed picture of the sea floor

Page 5: Marine Provinces

Bathymetric techniques

• Low frequency sound is used to determine structure beneath the sea floor

Page 6: Marine Provinces

Bathymetric techniques• Satellites measure sea

surface elevation, which mimics sea floor bathymetry

Page 7: Marine Provinces

Continental Margin- submerged outer edge of the continent. Includes the continental shelf and slope.

Page 8: Marine Provinces

Features of the Underwater World

Continental shelf

Continental slope

Continental rise

Abyssal plain

Abyssal hills

Submarine canyon

Seamount

Guyot

Ridge

Trench

Page 9: Marine Provinces

continental shelfslope

rise

abyssal plain

abyssal hills

ridge

transform fault

Page 10: Marine Provinces

Continental Shelf:• shallow submerged extension of the

continent• more like the continent than the ocean

basin• important for mineral and oil deposits• 7.4% of Earth’s ocean area

Page 11: Marine Provinces

Continental slope:

• the transition between the gently descending cont. shelf and deep-ocean basin

• generally, 4 - 25o slope, 12 miles wide, 12,000ft deep

Continental Rise:

• accumulation of sediment from turbidity currents

• like an avalanche

Page 12: Marine Provinces

Shelf width depends on:

1. proximity to plate boundary (passive vs active margin)

2. sea level

3. fast moving ocean currents

Page 13: Marine Provinces

Proximity to Plate Boundary

Page 14: Marine Provinces

Passive versus active continental margins

Passive margin

– No plate boundary

Shelf

Slope

Rise

– E.g., eastern coasts of N. and S. America

– No volcanism

Page 15: Marine Provinces

Passive versus active continental margins

Active margin

Plate boundary

Convergence zone

volcanism, many earthquakes, and active mountain building

E.g., California, Chilean (e.g., Peru, Chile), Marianas (e.g., Japan, Marianas)

Page 16: Marine Provinces

Sea Level Change

Page 17: Marine Provinces

Fast Moving Ocean Currents

Page 18: Marine Provinces

Abyssal plain:

flat featureless expanses of sediment formed by suspension settling

common in Atlantic

Abyssal hills:

small sediment covered extinct volcanoes

< 650 ft high

Page 19: Marine Provinces

Sea mount: volcanic projections that don’t rise above the surface of the sea

circular or elliptically shaped

many form at hot spots

Page 20: Marine Provinces

Guyot: flat topped sea mounts

Page 21: Marine Provinces

Submarine canyons:

Canyons that cut into continental shelf

Turbidity currents carve submarine canyons into the slope and shelf

Page 22: Marine Provinces

Submarine canyons and deep-sea fans

• Moves sediment movement from the continents into the deep-sea via turbidity currents

• Debris from turbidity currents creates graded bedding deposits and deep-sea fans

Page 23: Marine Provinces

Diver in the La Jolla Submarine Canyon

Page 24: Marine Provinces

Ridges: mountainous chain of young basaltic rock at the active spreading center of the ocean

Page 25: Marine Provinces

The Mid-Atlantic Ridge

• Traverses the center of the Atlantic Ocean

• Contains a central down-dropped rift valley

• Surfaces in Iceland

Page 26: Marine Provinces

Features of the mid-ocean ridge

• Rift valleys– Form when

plates split apart

– Down-dropped areas associated with faults and earthquakes

Page 27: Marine Provinces

Trenches: arc-shaped depression in the deep ocean floor

• Formed by plate convergence• Associated with volcanic arcs

– Island arc– Continental arc

• Most active geologic feature on earth

Page 28: Marine Provinces

Ocean trenches

• Most trenches are in the Pacific Ocean

Page 29: Marine Provinces

Location of Marianas Trench

Page 30: Marine Provinces

Location of Mariana Trench

Page 31: Marine Provinces
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Ocean sediment

• Particles of organic or inorganic matter that settle through the water column and accumulate in a loose, unconsolidated form on the ocean floor

• Layers represent a record of Earth history, including:– Movement of tectonic plates– Past changes in climate– Ancient ocean circulation patterns– Cataclysmic events

Page 34: Marine Provinces

Collecting ocean sediment

• Specially designed ships collect cores by rotary drilling

• Cores allow scientists to analyze ocean sediment

Page 35: Marine Provinces

Sediment origin & compositionSediment origin & composition

Origin:1. Weathering and erosion2. Activity of living organisms3. Accumulation of dead organisms- oozes4. Volcanic eruptions5. Chemical processes within the water itself6. Space debris

Composition:Boulder >256mm Sand 0.062-2mmCobble 64-256mm Silt 0.004-

0.062mmPebble 4-64mm Clay <0.004Granule 2-4mm

Page 36: Marine Provinces

Sources of SedimentSources of SedimentTerrigenous:

1. Continental runoff- desert sand blows off continent to ocean

2. Volcanic eruptions- dust and magma3. Rivers- washout of sediment

Mt. St. Helens

Page 37: Marine Provinces

Biogenous:• Mostly calcareous and siliceous

• Abundant where ample nutrients encourage high biological productivity

• Parrotfish

• Oozes: pelagic sediment

containing >30% by volume

microorganism shells

Page 38: Marine Provinces

Biogenous sediment composition

• Microscopic biogenous tests are composed of 2 main chemical compounds:

1. Silica (SiO2) including opal (SiO2 · nH2O)

Diatoms (algae)

Radiolarians (protozoan)

2. Calcium carbonate or calcite (CaCO3)

Coccolithophores (algae)

Foraminifers (protozoan)

Page 39: Marine Provinces

Calcareous Oozes

pteropod

CoccolithophoresForaminifers

Page 40: Marine Provinces

Siliceous Oozes

radiolarian diatom

Page 41: Marine Provinces

Biogenous ooze turns to rock

• When biogenous ooze hardens and lithifies, can form:– Diatomaceous

earth (if composed of diatom-rich ooze)

– Chalk (if composed of coccolith-rich ooze)

Chalk cliffs of southern England

Page 42: Marine Provinces

Distribution of biogenous ooze

• Most biogenous ooze found as pelagic deposits

• Factors affecting the distribution of biogenous ooze:– Productivity (amount of organisms in

surface waters)– Destruction (dissolving at depth)– Dilution (mixing with lithogenous clays)

Page 43: Marine Provinces

Hydrogenous sediment

• Hydrogenous sediment forms when dissolved materials come out of solution (precipitate)

• Precipitation is caused by a change in conditions including:– Changes in temperature– Changes in pressure– Addition of chemically active fluids

Page 44: Marine Provinces

Types of hydrogenous sediment

Manganese nodules

Phosphates

Carbonates

Metal sulfides

Evaporite salts

Page 45: Marine Provinces

Magnesium nodules:• 1st discovered by Challenger expedition (1873-76)• 16 million tons accumulate each year• Growth rate: 1-10 mm/million years• Need nuclei to form

Mining has not developed because:1. Low international market price for metals2. Unresolved legal ownership problems3. Technical costs and development4. Effect on hydrothermal vent communities unknown

Mining manganese

nodules

Page 46: Marine Provinces

Cosmogenous sediments:

• Extraterrestrial in origin

• Two main types:

Microscopic space dust

Macroscopic meteor debris Diatoms (algae)

• Forms an insignificant proportion of ocean sediment

tektites

Page 47: Marine Provinces

Studying sediments

• Learn about past climates• Ocean circulation• Plate tectonics

O2 isotope stratigraphy:O2

16 (most abundant): O218 (next abundant)

O216 has higher vapor pressure

At a given time when a shell forms in cold water, more O2

18 goes in relative to O216

Page 48: Marine Provinces

Map of the World Ocean showing generalized distribution of the principal kinds of sediment on the ocean floor

Page 49: Marine Provinces

Deep Ocean Characteristics

• Cold• Still• Stable• Dark• Essentially no productivity• Sparse Life• Extremely high pressure• Little food

Page 50: Marine Provinces

Deep sea orgs are dependant upon surface production from:

Dead phytoplankton, zooplankton, fish, mammals

Fecal pellets and crustacean molts

Macrophyte detritus

Animal migrations

Page 51: Marine Provinces

Potential food source for deep sea organisms

Page 52: Marine Provinces

Scavengers can feed on carcass in less than 6 months

Whale Fall; i.e., marine snow

Page 53: Marine Provinces

Factors affecting organic material reaching the sea floor:

Storms

Seasonal variation

Page 54: Marine Provinces
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100m

dysphotic

aphotic

photic

Page 56: Marine Provinces
Page 57: Marine Provinces

• Ballard & Grassle (1977)- Alvin to Galapagos • Sulfur-rich vents 660 oF, but quickly cool to 73 oF• Thermophilic bacteria associated with vent

communities

Page 58: Marine Provinces

Hydrothermal vents found at mid-ocean ridge spreading centers.

Page 59: Marine Provinces

Active hydrothermal vents were first discovered at Loihi in the late 1980's

Page 60: Marine Provinces

Loihi

• 15 mi S.E. of Kilauea

• 3,178 ft below sea level

• Will reach sea level in ~10,000 yrs

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Loihi

Page 63: Marine Provinces

1. Cold seawater sinks into cracks deep into ocean floor

2. Water heated by magma rises and leaches out minerals from surrounding rocks

3. The water emerges from vents and precipitates out minerals

Page 64: Marine Provinces

magma

Bottom current

Seawater seepage

basalt

660oF

FeS, FeS2, CuFeS2

H2SFe, Mg

magma

Bottom current

Seawater seepage

basalt

660oF

FeS, FeS2, CuFeS2

H2SFe, Mg

Page 65: Marine Provinces
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Tube worms- pogonophoransOther orgs: • Calyptogena- large white clam• Large crabs• Sea anemones• Shrimp

Page 68: Marine Provinces

Support communities with high biomass, but low diversity

Primary producers are chemosynthetic bacteria

90% endemism

Communities are small (25-60m in diameter)

Page 69: Marine Provinces

Chemosynthesis:Oxygen + hydrogen sulfide + water + carbon dioxidesugar + sulfuric acid

602 + 6H2S + 6H20 + 6C02 C6H12O6 + 6H2S04

                                                 

             

Page 70: Marine Provinces

Photosynthesis:6H2O + 6CO2 + nutrients + light energy C6H12O6 + 6O2

Chemosynthesis:

602 + 6H2S + 6H20 + 6C02 C6H12O6 + 6H2S04

Page 71: Marine Provinces

Inquiry

1. What 3 factors effect shelf width?

2. Where are maganese nodules

located?

3. Radiolarians found in sediment form

______ ooze?

4. What does endemism mean?

5. How does the tubeworm get its

energy?

6. How does a hydrothermal vent form?