Title: Bathymetry of the Ocean Floor
1Bathymetry of the Ocean Floor
- echo soundings (1920s)
- ocean was not deepest in the center
2Echo sounding- not always accurate
Fig. 4-2a, p. 79
3Figure 3.1- An Echo Sounding of US East Coast
4Figure 3.3- Side-scan SONAR (Sound Navigation and
Ranging)
5Figure 3.2- Multibeam SONAR (Sound Navigation And
Ranging)
6Satellites Can Be Used to Map Seabed Contours
With the use of satellite altimetry, sea surface
levels can be measured more accurately, showing
sea surface distortion. (left) Distortion of the
sea surface above a seabed feature occurs when
the extra gravitational attraction of the feature
pulls water toward it from the sides, forming a
mound of water over itself.
7Figure 3.B
8Figure 3.C
9Figure 3.5
10Figure 3.6
11Fig. 4-5, p. 82
12Figure 3.7
13Shape of the Ocean Floor
- shallow extensions of the continents extended
seaward underwater
14Figure 3.8
15Shape of the Ocean Floor
- Submerged outer edge of the continents are called
continental margins - Deep-sea floor beyond these is called the ocean
basin
16Fig. 4-7, p. 83
17Continental Margins
- Passive margins
- continental margins not located on plate
boundaries - Atlantic-type margins
18Continental Margins
- Active margins-
- continental margins on the edge of convergent or
transform plate boundaries - Pacific-type margins
19Fig. 4-8, p. 84
20Figure 3.7
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23Continental Margins
- Continental Shelves
- Shallow, submerged extension of a continent
- broad, gently sloping
24Figure 3.8
25Fig. 4-9, p. 85
26Continental Margins
- Width of Continental Shelf is determined by
- proximity to a plate boundary
- current speed in the region
- sea-level
27Fig. 4-8, p. 84
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29Continental Margins
- Shelf break
- transition between the continental shelf and the
continental slope - Occurs at about 140m (360 ft)
- Continental Slopes
- Steeper than the shelf
30Figure 3.8
31Continental Margins
- Continental rises
- base of continental slope covered by a blanket of
accumulated sediment - gradual slope
- on Passive margins only
32Fig. 4-9, p. 85
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34Fig. 4-7, p. 83
35Figure 3.6
36Continental Margins
- Submarine Canyons
- cut into the continental shelf and slope
- formed by turbidity currents (avalanche-like
sediment movements)
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38Figure 3.10a
39Submarine Canyon Off of The coast Of New Jersey
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41Figure 3.11
42Ocean Basin
- thick layer of sediment (up to 5 km or 3mi thick)
covering basaltic rocks - Make up more than ½ of the earths surface
43Ocean Basin
- Oceanic ridges
- Underwater mountain chain
- an active spreading center
- offset at regular intervals by transform faults
44Fig. 4-16a, p. 89
45Figure 3.15
46Figure 3.19
47Ocean Basin
- Hydrothermal vents
- 1977 Robert Ballard J F Grassle
- average temp is about 8-16oC (46-61oF) much
warmer than the typical 3-4oC (37-39oF) - support a unique community of organisms that
depend on chemosynthetic bacteria
48Figure 3.17
49Fig. 4-19, p. 91
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51Figure 2.26
52Ocean Basin
- Seamounts
- Inactive volcanoes that do not rise above the
surface of the ocean - They are tall with steep slopes
- Guyots or Tablemounts
- Flat-topped seamounts that were eroded by wave
action - Abyssal Hills
- abundant, small sediment-covered extinct volcanoes
53Ocean Basin
- Abyssal Plains
- Flat, featureless, sediment-covered ocean floor
54Figure 3.12
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56Ocean Basin
- Trenches
- Arc-shaped depression in the deep seafloor
- a converging oceanic plate is subducted
57Figure 3.13
58Figure 3.14
59Fig. 4-25, p. 96
60Ocean Basin
- Island Arcs
- Curving chains of volcanic islands and seamounts
found paralleling the edge of trenches
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62Figure 3.C