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Sea Floor & Sediments Measuring the Depths Soundings Echo Sounder.

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Presentation on theme: "Sea Floor & Sediments Measuring the Depths Soundings Echo Sounder."— Presentation transcript:

1 Sea Floor & Sediments Measuring the Depths Soundings Echo Sounder

2 Measuring the Depths Modern Tools ROV’s LADS Side-scan Sonar Satellites

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4 Sea Floor Bathymetry

5 Continental Margin Active margin Leading margin Pacific-type Convergent boundary Continental shelf is narrow and irregular

6 Continental Margin Passive margin Trailing margin Atlantic-type Divergent boundary Sediment build-up on shelf

7 Continental Shelf

8 Formation

9 Shelf Break & Slope

10 Submarine Canyons

11 Turbidity Currents Turbidites

12 Continental Rise Atlantic, Indian, and Antarctic Oceans Not usually found at active margins

13 Ocean Basin Floor

14 Abyssal Hills & Seamounts Abyssal hills Most common topographic feature < 1000m Seamounts Steep-sided volcanoes > 1000m

15 Abyssal Hills & Seamounts Guyots (gee-ohs) Flat-topped seamounts

16 Coral Reefs

17 Trenches

18 Sediments Rate of accumulation Distribution Source & abundance Chemical composition History

19 Particle Size

20 Size & shape Influences sinking rate and travel time

21 Particle Size Particle aggregation Electrical attraction Fecal pellets 2200x

22 Location Neritic Continental margins & islands Pelagic Found on the deep sea floor

23 Location

24 Rates of Deposits Neritic Sediments Highly variable River estuaries Quiet bays Relict Sediments

25 Rates of Deposit Pelagic Sediments Slower than neritic m

26 Source & Chemistry 4 sources: 1. Preexisting rocks 2. Marine organisms 3. Seawater 4. Space

27 Lithogenous Sediments Terrigenous sediments Fine to coarse Most common Weathering of rocks Transport by rivers, winds, volcanoes and glaciers

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29 Lithogenous Sediments Terrigenous sediments Dominant neritic sediment Clear size distribution

30 Lithogenous Sediments Pelagic lithogenous sediments Abyssal clay 70% clay-size particles 0.1 cm per 1000 years! Red clay Due to oxidation of iron

31 Lithogenous Sediments 4 types of clay minerals: 1. Chlorite

32 Lithogenous Sediments 4 types of clay minerals: 2. Kaolinite

33 Lithogenous Sediments 4 types of clay minerals: 3. Illite

34 Lithogenous Sediments 4 types of clay minerals: 4. Montmorillonite

35 Biogenous Sediments Fine to coarse 2 nd most common Shells & skeletons CaCO 3 [calcareous] SiO 3 [siliceous] Oozes

36 Biogenous Sediments Coccolithophorids Pteropods Foraminfera Lysocline

37 Carbonate Compensation Depth The depth at which the amount of calcareous material preserved falls below 20% of the total sediment

38 Biogenous Sediments Diatoms Radiolarians

39 Hydrogenous Sediments Derived from chemical reactions in the water

40 Hydrogenous Sediments Carbonates Limestone-type deposits Shallow, warm water Ooliths

41 Hydrogenous Sediments Phosphorites Phosphorus in the form of phosphate Continental shelf & slope

42 Hydrogenous Sediments Salts High rate of evaporation in shallow areas Carbonate salts, sulfate salts, then chlorides

43 Hydrogenous Sediments Manganese nodules Manganese, iron, nickel, cobalt & copper

44 Cosmogenous Sediments Sediments derived from space

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46 Lithification Formation of sedimentary rock Temps <200ºC

47 Diagenesis Chemical changes of sediments when they react with seawater

48 Sampling Methods Dredges Large bulk samples Benthic organisms

49 Sampling Methods Grab samplers Mud & sand Quantitative sampling

50 Sampling Methods Corers Gravity corer 1-2 m cores

51 Sampling Methods Corers Piston corer Up to 20 m cores

52 Sampling Methods Corers Box corer Large, undisturbed samples Door

53 Sampling Methods Platform drilling JOIDES Resolution 1100 m cores

54 Sampling Methods Acoustic profiling

55 Sediments as Historical Records Paleoceanography Chemistry of biogenous sediments Ratio of 18 O: 16 O Proportion of these in skeletons reflects abundance of isotopes in water

56 Seabed Resources Sand & Gravel Annual world production = 1.2 billion metric tons Only significant seabed mining done in the US

57 Seabed Resources Phosphorite Mined to produce phosphate fertilizers Substantial source in Onslow Bay, NC

58 Seabed Resources Sulfur Used for production of sulfuric acid

59 Seabed Resources Coal Produced by burial of plant material in areas of low oxygen Peat

60 Seabed Resources Oil & Gas Represent >95% of the value of all resources extracted from the sea floor Sedimentary rocks million years old

61 Seabed Resources Gas Hydrates Combo of natural gas (CH 4 ) and water Ice-like structure

62 Seabed Resources Manganese Nodules Manganese, copper, nickel & cobalt Cobalt is of particular interest


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