1. Alvin, the most famous and accomplished of the small research submarines, is reaching the end of its operational life.
Fig. 4-CO, p. 97

2. Figure 4. 1: Seamen handling the steam winch aboard HMS Challenger
Figure 4.1: Seamen handling the steam winch aboard HMS Challenger. The winch was used to lower a weight on the end of a line to the seabed to find the ocean depth. This illustration is from the Challenger Report (1880).
Fig. 4-1, p. 99

3. Fig. 4-2a, p. 100 Figure 4.2: How an echo sounder operates.
(a) Echo sounders sense the contour of the seafloor by beaming sound waves to the bottom and measuring the time required for the sound waves to bounce back to the ship. If the round-trip travel time and wave velocity are known, distance to the bottom can be calculated. The depth is equal to the velocity of sound waves in seawater (V) times one-half the time (T) required for sound to travel from the source to the bottom and back to the receiver.
Fig. 4-2a, p. 100

4. Beam of sound waves travels to bottom and is reflected back
to ship
Depth = V (T/2)
Figure 4.2: How an echo sounder operates.
(a) Echo sounders sense the contour of the seafloor by beaming sound waves to the bottom and measuring the time required for the sound waves to bounce back to the ship. If the round-trip travel time and wave velocity are known, distance to the bottom can be calculated. The depth is equal to the velocity of sound waves in seawater (V) times one-half the time (T) required for sound to travel from the source to the bottom and back to the receiver.
Fig. 4-2a, p. 100

5. Fig. 4-2b, p. 100 Figure 4.2: How an echo sounder operates.
(b) The accuracy of an echo sounder can be affected by water conditions and bottom contours. The pulses of sound energy, or “pings,” from the sounder spread out in a narrow cone as they travel from the ship. When depth is great, the sounds reflect from a large area of seabed. Because the first sound of the returning echo is used to sense depth, measurements over deep depressions are often inaccurate.
Fig. 4-2b, p. 100

6. echo sounder (beam angle is exaggerated) Measured depth
is less than
actual depth
Sound beam emitted by
echo sounder (beam angle is exaggerated)
Measured depth
equals true depth
beneath vessel
True depth immediately
Seafloor
Figure 4.2: How an echo sounder operates.
(b) The accuracy of an echo sounder can be affected by water conditions and bottom contours. The pulses of sound energy, or “pings,” from the sounder spread out in a narrow cone as they travel from the ship. When depth is great, the sounds reflect from a large area of seabed. Because the first sound of the returning echo is used to sense depth, measurements over deep depressions are often inaccurate.
Fig. 4-2b, p. 100

7. Fig. 4-2c, p. 100 Figure 4.2: How an echo sounder operates.
(c) An echo sounder trace. A sound pulse from a ship is reflected off the seabed and returns to the ship. Transit time provides a measure of depth. For example, it takes about 2 seconds for a sound pulse to strike the bottom and return to the ship when the water depth is 1,500 meters (4,900 feet). Bottom contours are revealed as the ship sails a steady course. In this trace, the horizontal axis represents the course of the ship; the vertical axis represents the water depth. The ship has sailed over a small submarine canyon.
Fig. 4-2c, p. 100

8. Figure 4.3: Marie Tharp and geologist Bruce Heezen study the final version of Heinrich Berann’s World Ocean Floor Panorama in Berann’s studio, Austria, Berann was engaged by the U.S. Navy and the National Geographic Society to incorporate Tharp’s work and data from other sources in a unified form. One of Berann’s beautiful maps is included as Figure 4.22.
Fig. 4-3, p. 101

9. Fig. 4-4a, p. 101 Figure 4.4: How a multibeam system collects data.
(a) A multibeam echo sounder uses as many as 121 beams radiating from a ship’s hull. Fanning out at right angles to the direction of travel, these beams can cover a 120 arc and measure a swath of bottom about 3.4 times as wide as the water is deep. Typically, a “ping” is sent toward the seabed every 10 seconds. Listening devices record sounds reflected from the bottom, but only from the narrow corridors corresponding to the outgoing pulse. Thus, a multibeam system is much less susceptible to contour error than the single-beam device shown in Figure 4.2.
Fig. 4-4a, p. 101

10. Fig. 4-4b, p. 101 Figure 4.4: How a multibeam system collects data.
(b) A multibeam record of a fragment of seafloor near the East Pacific Rise south of the tip of Baja California, Mexico. The uneven coverage reflects the path of the ship across the surface. Detailed analysis requires sailing a careful back-and-forth pattern. Computer processing provides extraordinarily detailed images, such as those in Figures 4.12, 4.13, and 4.14.
Fig. 4-4b, p. 101

11. (a) ABE being launched from a Woods Hole ship.
Box 4-1a, p. 102

12. (b) A typical mission profile for ABE
(b) A typical mission profile for ABE. After checking its onboard systems, the autonomous explorer spirals to its working depth with the aid of a heavy weight. It jettisons the weight, becomes neutrally buoyant, and begins to “mow the lawn” with its multibeam sensors. It then moves to another area and descends closer to the seabed to take photographs or use its magnetic sensors. When the mission is complete and the batteries depleted, ABE will jettison a second set of weights and rise to the surface (not shown).
Box 4-1b, p. 103

13. 500
1,000
1,500
Depth (m)
2,000
−200
(b) A typical mission profile for ABE. After checking its onboard systems, the autonomous explorer spirals to its working depth with the aid of a heavy weight. It jettisons the weight, becomes neutrally buoyant, and begins to “mow the lawn” with its multibeam sensors. It then moves to another area and descends closer to the seabed to take photographs or use its magnetic sensors. When the mission is complete and the batteries depleted, ABE will jettison a second set of weights and rise to the surface (not shown).
−400
X (m)
2,500
−600
−800
3,000
−5,000
−5,500
−6,000
Y (m)
Box 4-1b, p. 103

14. (c) A multibeam bathymetric map made from the dive in Figure b.
Box 4-1c, p. 103

15.
Latitude
(c) A multibeam bathymetric map made from the dive in Figure b.
−130
−130
−130
−130
−16.5
−16.0
−15.5
−15.0
Longitude
Box 4-1c, p. 103

16. Fig. 4-5a, p. 104 Figure 4.5: Satellite altimetry.
(a) Geosat, a U.S. Navy satellite that operated from 1985 through 1990, provided measurements of sea-surface height from orbit. Moving above the ocean surface at 7 kilometers (4 miles) a second, Geosat bounced a thousand pulses of radar energy off the ocean every second; its measurements were accurate to within 0.03 meter (1 inch).
Fig. 4-5a, p. 104

17. Figure 4.5: Satellite altimetry.
(b) Differences in sea-surface height above a seabed feature are caused by the extra gravitational attraction of the feature, which “pulls” water toward it from the sides and forms a mound of water over itself.

18. Geosat Orbit h Sea Surface Ocean Seafloor Crust Fig. 4-5b, p. 104
Figure 4.5: Satellite altimetry.
(b) Differences in sea-surface height above a seabed feature are caused by the extra gravitational attraction of the feature, which “pulls” water toward it from the sides and forms a mound of water over itself.
Sea Surface
Ocean
Seafloor
Crust
Fig. 4-5b, p. 104

19. Fig. 4-5c, p. 104 Figure 4.5: Satellite altimetry.
(c) This view of the complex system of ridges, trenches, and fracture zones on the south Atlantic seafloor east of the tips of South America and Antarctica’s Palmer Peninsula was derived in large part from Geosat data declassified by the U.S. Navy in 1995.
Fig. 4-5c, p. 104

20. Figure 4.6: Cross sections of the Atlantic Ocean basin and the continental United States, showing the range of elevations. The vertical exaggeration is 100:1. Although ocean depth is clearly greater than the average height of the continent, the general range of contours is similar.
Fig. 4-6, p. 105

21. Figure 4.6: Cross sections of the Atlantic Ocean basin and the continental United States, showing the range of elevations. The vertical exaggeration is 100:1. Although ocean depth is clearly greater than the average height of the continent, the general range of contours is similar.
Fig. 4-6a, p. 105

22. Figure 4.6: Cross sections of the Atlantic Ocean basin and the continental United States, showing the range of elevations. The vertical exaggeration is 100:1. Although ocean depth is clearly greater than the average height of the continent, the general range of contours is similar.
Fig. 4-6b, p. 105

23. Appalachian Mountains
Height in meters
Height in feet
Sierra Nevada
Rocky Mountains
4,572
15,000
3,048
Appalachian Mountains
10,000
1,524
5,000
–1,524
–5,000
–3,048
–10,000
–4,572
–15,000
–6,096
South America
Atlantic Ridge
Africa
–20,000
100
200
300
400
500
Horizontal scale in nautical miles
Figure 4.6: Cross sections of the Atlantic Ocean basin and the continental United States, showing the range of elevations. The vertical exaggeration is 100:1. Although ocean depth is clearly greater than the average height of the continent, the general range of contours is similar.
Depth in feet
200
400
600
Depth in meters
Horizontal scale in kilometers
Vertical x 100
Fig. 4-6b, p. 105

24. Figure 4.7: A graph showing the distribution of elevations and depths on Earth. There are two dominant levels on our planet, one exposed and the other submerged. This curve is not a land-to-sea profile of Earth, but rather a plot of the area of Earth’s surface above any given elevation or depth below sea level. Note that more than half of Earth’s solid surface is at least 3,000 meters (10,000 feet) below sea level. The average depth of the world ocean (3,796 meters, or 12,451 feet) is much greater than the average height of the continents (840 meters, or 2,760 feet).
Fig. 4-7, p. 105

25. Earth’s area (hundreds of millions of square kilometers)
Mount Everest 8.85 km (5.5 mi)
Elevation (kilometers)
Elevation (miles)
Mean land elevation 840 m (2,760 ft)
Sea level
Mean depth of sea 3,796 m (12,451 ft)
Depth (miles)
Figure 4.7: A graph showing the distribution of elevations and depths on Earth. There are two dominant levels on our planet, one exposed and the other submerged. This curve is not a land-to-sea profile of Earth, but rather a plot of the area of Earth’s surface above any given elevation or depth below sea level. Note that more than half of Earth’s solid surface is at least 3,000 meters (10,000 feet) below sea level. The average depth of the world ocean (3,796 meters, or 12,451 feet) is much greater than the average height of the continents (840 meters, or 2,760 feet).
Depth (kilometers)
Mariana Trench ~11 km
% Earth’s area at this elevation or higher
Fig. 4-7, p. 105

26. Figure 4.8: A cross section of a typical ocean basin flanked by passive continental margins. The vertical scale has been greatly exaggerated to emphasize the basin contours.
Fig. 4-8, p. 106

27. Submarine canyon profile (cut through continental shelf) Sediment
Continental margin
Deep-ocean basin
Continental margin
Submarine canyon profile (cut through continental shelf)
Sediment
Continental shelf
Continental slope
Oceanic ridge
Sediment
Continental rise
Continental
crust (granitic)
Continental
crust (granitic)
Figure 4.8: A cross section of a typical ocean basin flanked by passive continental margins. The vertical scale has been greatly exaggerated to emphasize the basin contours.
Oceanic
crust (basaltic)
Oceanic
crust (basaltic)
Asthenosphere
Fig. 4-8, p. 106

28. Figure 4.9: Features of Earth’s solid surface shown as percentages of the planet’s total surface.
Fig. 4-9, p. 106

29. Continental shelves and slopes
Continental mountains 10.3%
Ocean 70.8%
Land 29.2%
Oceanic ridges 22.1%
Continental lowlands 18.9%
Continental shelves and slopes
11.4%
Ocean basin floors 29.8%
Figure 4.9: Features of Earth’s solid surface shown as percentages of the planet’s total surface.
Volcanic island arcs, trenches, submarine volcanoes, and hills 3.7%
Continental rise 3.8%
Oceanic crust
Continental crust
Fig. 4-9, p. 106

30. Figure 4.10: Typical continental margins bordering the tectonically active (Pacific-type) and tectonically passive (Atlantic-type) edges of a moving continent. The vertical scale has been exaggerated.
Fig. 4-10, p. 107

31. An active margin A passive margin
Narrow continental shelf
A passive margin
Peru–Chile Trench
Plate boundary
Andes Mountains
Plate boundary
Broad
continental shelf
South America
Atlantic Ocean
Pacific Ocean
South American Plate
Deep basin
Nazca Plate
African Plate
Plate movement
Plate movement
Plate movement
Subduction zone (deep and shallow earthquakes)
Mid-Atlantic Ridge (spreading centers, shallow earthquakes)
Figure 4.10: Typical continental margins bordering the tectonically active (Pacific-type) and tectonically passive (Atlantic-type) edges of a moving continent. The vertical scale has been exaggerated.
Fig. 4-10, p. 107

32. Figure 4.11: The features of a passive continental margin.
Fig. 4-11, p. 108

33. Continental margin Continental shelf
Distance from shore (miles)
100
200
300
400
500
600
700
Continental margin
Continental shelf
Sea level
Shelf break (~140 m, 460 ft) 1
Continental rise
Depth (km) 1
(sediment thickness varies) 2
Depth (miles) 3
Continental slope 2 4
Deep-ocean floor 3 5
Figure 4.11: The features of a passive continental margin.
100
200
300
400
500
600
700
800
900
1,000 1,100 1,200
Vertical exaggeration 50:1.
Distance from shore (km)
Sea level
Depth (km) 4
100
200
300
400
500
600
700
800
900
1,000 1,100 1,200
No vertical exaggeration.
Fig. 4-11, p. 108

34. Figure 4. 12: A cliff more than 1
Figure 4.12: A cliff more than 1.6 kilometers (1 mile) high marks the edge of the continental shelf west of central Florida. The very steep continental slope seen here is unusual. Perhaps fresh water seeping from the adjacent land undermined the slope and caused it to collapse. Currents have removed much of the material that would otherwise be found at the base of the slope. Vertical exaggeration is about 50:1. Multibeam systems were used to obtain data for this image (and for Figures 4.13 and 4.14).
Fig. 4-12, p. 108

35. Figure 4.13: The broad continental shelf along the edge of the Gulf of Mexico south of Texas and Louisiana (looking east). Sediments carried by the Mississippi River have overlain ancient salt deposits. The weight of the sediments causes salt domes to form and dissolve, leaving pockmarks in the continental shelf.
Fig. 4-13, p. 109

36. Figure 4.14: The complex continental shelf off central California, typical of an active margin. Compare to Figure 4.12.
Fig. 4-14, p. 109

37. Figure 4.15: Changes in sea level over the last 250,000 years, as traced by data taken from ocean-floor cores. The rise and fall of sea level is due largely to the coming and going of ice ages—periods of increased and decreased glaciation, respectively. Because water that formed the ice-age glaciers came from the ocean, sea level dropped. Point a indicates a low stand of 125 meters (410 feet) at the climax of the last ice age some 18,000 years ago. Point b indicates a high stand of 6 meters (19.7 feet) during the last interglacial period about 120,000 years ago. Point c shows the present sea level. Sea level continues to rise as we emerge from the last ice age and enter an accelerating period of global warming.
Fig. 4-15, p. 110

38. Height above or below present sea level (ft)
Today’s sea level
Height above or below present sea level (m)
Height above or below present sea level (ft)
–130
–426
Figure 4.15: Changes in sea level over the last 250,000 years, as traced by data taken from ocean-floor cores. The rise and fall of sea level is due largely to the coming and going of ice ages—periods of increased and decreased glaciation, respectively. Because water that formed the ice-age glaciers came from the ocean, sea level dropped. Point a indicates a low stand of 125 meters (410 feet) at the climax of the last ice age some 18,000 years ago. Point b indicates a high stand of 6 meters (19.7 feet) during the last interglacial period about 120,000 years ago. Point c shows the present sea level. Sea level continues to rise as we emerge from the last ice age and enter an accelerating period of global warming.
50,000
100,000
150,000
200,000
250,000
Years before present
Fig. 4-15, p. 110

39. Figure 4.16: A submarine canyon.
Fig. 4-16, p. 111

40. Canyon heads Shelf break Continental shelf Deep-sea fan
Continental slope
Distribution channel
Figure 4.16: A submarine canyon.
Fig. 4-16, p. 111

41. Figure 4.17: A multibeam sonar image of Hudson Canyon east of New Jersey. The shelf in this area is broad. The canyon can be seen nicking the shelf–slope junction and then continuing toward the abyssal plain to the southwest. The underwater topography has been exaggerated by a factor of 5 relative to the land topography. The fine black line marks sea level.
Fig. 4-17, p. 111

42. Figure 4.18: A turbidity current flowing down a submerged slope off the island of Jamaica. A turbidity current is not propelled by the water within it but by gravity. The propeller of a submarine caused the turbidity current by disturbing sediment along the slope.
Fig. 4-18, p. 112

43. Figure 4.19: A continuous cascade of sediment at the head of San Lucas submarine canyon (off the coast of Baja California, Mexico), which assists in eroding the narrow gorge in conjunction with occasional turbidity currents. About 200,000 cubic meters (260,000 cubic yards) of sediment flows annually into the head of Scripps Canyon, a slightly larger submarine canyon north of San Diego, California.
Fig. 4-19, p. 112

44. Figure 4.20: Large stationary waves of sediment deposited at the base of the continental rise in the western North Atlantic. Deep boundary currents pick up sediments and sweep them across the ocean floor. As the currents are forced around bends and across depressions, they slow and deposit the suspended material at the base of the rises in the form of ridges or mud waves.
Fig. 4-20, p. 112

45. Feet
Meters
4,390
14,400
15,000
4,570
Figure 4.20: Large stationary waves of sediment deposited at the base of the continental rise in the western North Atlantic. Deep boundary currents pick up sediments and sweep them across the ocean floor. As the currents are forced around bends and across depressions, they slow and deposit the suspended material at the base of the rises in the form of ridges or mud waves. 1 2 3 4 5
Miles
15,600
4,760 1 2 3 4 5 6
Kilometers
Depth
Fig. 4-20, p. 112

46. Figure 4.21a: The oceanic ridge system (in colors) stretches some 65,000 kilometers (40,000 miles) around Earth. If the ocean evaporated, the ridge system would surely be Earth’s most remarkable and obvious feature. The thickness of the red lines indicates the rate of spreading for some of the most rapidly spreading sections, and the numbers give spreading rates in centimeters per year. The East Pacific Rise typically spreads about 6 times as fast as the Mid-Atlantic Ridge.
Fig. 4-21a, p. 114

47. Mid-Atlantic Ridge Juan de Fuca Ridge Indian Ridge
2.6
East Pacific
Rise (Ridge)
3.8
5.5
15.7
2.8
10.7
9.5
9.5
Indian Ridge
Figure 4.21a: The oceanic ridge system (in colors) stretches some 65,000 kilometers (40,000 miles) around Earth. If the ocean evaporated, the ridge system would surely be Earth’s most remarkable and obvious feature. The thickness of the red lines indicates the rate of spreading for some of the most rapidly spreading sections, and the numbers give spreading rates in centimeters per year. The East Pacific Rise typically spreads about 6 times as fast as the Mid-Atlantic Ridge.
6.4
6.4
Pacific–Antarctic Ridge
1.5
Fig. 4-21a, p. 114

48. Figure 4.21b: Rapid spreading at the East Pacifi c Rise (lower image) spreads ridge features over a greater area. The slower spreading along the Mid-Atlantic Ridge concentrates the features in a smaller area with more pronounced contours. The relatively slow-spreading ridge is shown in more detail in Figure 4.23a. From J. A. Goff, W. H. F. Smith, K. M. Marks “The Contributions of Abyssal Hill Morphology and Noise to Altimetric Gravity Fabric” Oceanography Magazine Vol. 17, No. 1, page 36. Reprinted by permission of Oceanography Magazine/The Oceanography Society.
Fig. 4-21b, p. 114

49. Figure 4.22: Heinrich Berann’s hand-drawn map of a portion of the Atlantic Ocean floor showing some major oceanic features: oceanic ridge, transform faults, fracture zones, submarine canyons, seamounts, continental rises, trenches, and abyssal plains. Depths are in feet. The map is vertically exaggerated.
Fig. 4-22, p. 115

50. Figure 4.23a: The fine structure of the central portion of the Mid-Atlantic Ridge between Florida and western Africa. The depressed central valley (the spreading center, shown in blue) is clearly visible in this computer-generated multibeam image.
Fig. 4-23a, p. 116

51. Figure 4.23b: As this seismic profile shows, the rugged relief of the North Atlantic’s oceanic ridge is gradually being buried by slowly accumulating sediments.
Fig. 4-23b, p. 116

52. 3,940 meters; 12,000 feet 4,400 meters; 14,400 feet 28°N 50°W
Figure 4.23b: As this seismic profile shows, the rugged relief of the North Atlantic’s oceanic ridge is gradually being buried by slowly accumulating sediments.
10 miles
16 kilometers
Fig. 4-23b, p. 116

53. Figure 4.24: The Mid-Atlantic Ridge comes ashore in southwestern Iceland. The central rift (similar to that seen as the blue-colored contour in Figure 4.23a) is the valley in the middle distance. Notice the linear hills paralleling the rift and the steam issuing from thermal vents. If this part of the rift were submerged, these fumaroles would be hydrothermal vents similar to the one seen in Figure Reykjavik, Iceland’s largest city, is supplied with domestic hot water, hot water for space heating, and geothermally generated electricity from this valley.
Fig. 4-24, pp

54. Figure 4.25: Transform faults and fracture zones along an oceanic ridge. Transform faults are fractures along which lithospheric plates slide horizontally past one another. Transform faults are the active part of fracture zones. (For a larger-scale look at this process, please review Figure 3.25.)
Fig. 4-25, p. 118

55. Fracture zone (inactive) Fracture zone (inactive)
Plate boundary
Oceanic ridge
Adjacent sections here move in
same direction
Sections here move in opposite directions
Adjacent sections here move in same direction
Fracture zone (inactive)
Transform fault (active part of fracture zone)
Fracture zone (inactive)
Figure 4.25: Transform faults and fracture zones along an oceanic ridge. Transform faults are fractures along which lithospheric plates slide horizontally past one another. Transform faults are the active part of fracture zones. (For a larger-scale look at this process, please review Figure 3.25.)
Lithosphere
Asthenosphere
Fig. 4-25, p. 118

56. Figure 4.26: A black smoker discovered at a depth of about 2,800 meters (9,200 feet) along the East Pacific Rise.
Fig. 4-26, p. 119

57. Figure 4.27: A cross section of the central part of an oceanic ridge—similar to that shown in Figure 4.23a—showing the origin of hydrothermal vents. Cool water (blue arrows) is heated as it descends toward the hot magma chamber, leaching sulfur, iron, copper, zinc, and other materials from the surrounding rocks. The heated water (red arrows) returning to the surface carries these elements upward, discharging them at hydrothermal springs on the seafloor (or, rarely, as in the case in Iceland and Figure 4.24, to land). The areas around the vents support unique communities of organisms (see Chapter 16).
Fig. 4-27, p. 119

58. Hydrothermal vents and black smokers
Distance (km) 3 2 1 1 2 3 2 1 1 2
Distance (mi)
Spreading axis
Hydrothermal vents and black smokers
Figure 4.27: A cross section of the central part of an oceanic ridge—similar to that shown in Figure 4.23a—showing the origin of hydrothermal vents. Cool water (blue arrows) is heated as it descends toward the hot magma chamber, leaching sulfur, iron, copper, zinc, and other materials from the surrounding rocks. The heated water (red arrows) returning to the surface carries these elements upward, discharging them at hydrothermal springs on the seafloor (or, rarely, as in the case in Iceland and Figure 4.24, to land). The areas around the vents support unique communities of organisms (see Chapter 16).
Zone of leaching
Depth (km) 1
Depth (mi)
Ascending superheated seawater
Descending seawater 1 2
Magma chamber
Fig. 4-27, p. 119

59. Figure 4.28: The deep, smooth sediments of the Atlantic’s Northern Madeira Abyssal Plain bury 100-million-year-old mountains. The image was generated by a powerful echo sounder.
Fig. 4-28, p. 120

60. Figure 4. 29a: The process by which guyots (G) and seamounts (S) form
Figure 4.29a: The process by which guyots (G) and seamounts (S) form. Guyots have flat tops because they were once tall enough to be eroded by waves at the ocean’s surface. Seamounts have a similar origin but retain their more pointed volcano shape because they never reached the surface.
Fig. 4-29a, p. 120

61. Older, extinct volcanoes Older, extinct volcanoes
Inactive sinking volcano being "shaved" at ocean surface
Active volcanoes
Older, extinct volcanoes
Older, extinct volcanoes
Spreading center
Sea level G S G G G G S G
Magma chambers
Lithosphere
Figure 4.29a: The process by which guyots (G) and seamounts (S) form. Guyots have flat tops because they were once tall enough to be eroded by waves at the ocean’s surface. Seamounts have a similar origin but retain their more pointed volcano shape because they never reached the surface.
Asthenosphere
G = guyot S = seamount 50 40 30 20 10 10 20 30 40 50
Age of ocean floor (millions of years)
Fig. 4-29a, p. 120

62. Figure 4.29b: An undersea volcano east of the easternmost island of the Samoan chain in the Pacific. Vailulu’u, as it has been named, rises from an ocean depth of 4,800 meters (15,700 feet) to within 590 meters (1,900 feet) of the ocean surface.
Fig. 4-29b, p. 121

63. 169°08'W
168°04'W
14°12'S
169°00'W
Figure 4.29b: An undersea volcano east of the easternmost island of the Samoan chain in the Pacific. Vailulu’u, as it has been named, rises from an ocean depth of 4,800 meters (15,700 feet) to within 590 meters (1,900 feet) of the ocean surface.
14°16'S
168°56'W
14°20'S
168°52'W
14°24'S
Depth (m)
−5,000 −4,000 −3,000 −2,000 −1,000
−16,404 −13,123 −9,843 −6,562
−3,281
Depth (ft)
Fig. 4-29b, p. 121

64. Figure 4.29c: A new volcano grew inside Vailulu’u between 1999 and 2005.
Fig. 4-29c, p. 121

65. Figure 4. 30: Oceanic trenches of the world
Figure 4.30: Oceanic trenches of the world. Note their prevalence in the active Pacific.
Fig. 4-30, p. 122

66. Kermadec–Tonga Trench
Kuril Trench
Aleutian Trench
Philippine Trench
Japan Trench
Puerto Rico Trench
Mariana Trench
Challenger Deep
Middle America Trench
Kermadec–Tonga Trench
Java Trench
New Hebrides Trench
Peru–Chile Trench
Figure 4.30: Oceanic trenches of the world. Note their prevalence in the active Pacific.
South Sandwich Trench
Fig. 4-30, p. 122

67. Figure 4. 31: The Mariana Trench
Figure 4.31: The Mariana Trench. (a) Comparing the Challenger Deep and Mount Everest at the same scale shows that the deepest part of the Mariana Trench is about 20% as deep as the mountain is high. (b) The Mariana Trench shown without vertical exaggeration.
Fig. 4-31, p. 123

68. Mount Everest (...same scale) Challenger Deep
Guam
Mariana Trench
Pacific Ocean
Depth (km)
Depth (mi)
Mount Everest (...same scale)
Challenger Deep
Figure 4.31: The Mariana Trench. (a) Comparing the Challenger Deep and Mount Everest at the same scale shows that the deepest part of the Mariana Trench is about 20% as deep as the mountain is high. (b) The Mariana Trench shown without vertical exaggeration.
Guam
Mariana Trench
Fig. 4-31, p. 123

69. Figure 4.32: A technological tour de force: a map that shows all the features discussed in this chapter, derived from data provided to the National Geophysical Data Center from satellites and shipborne sensors. These features—and a basic understanding of the geological reasons for their existence—will help you recall the dramatic nature and history of the seafloor that we have discussed in the past two chapters.
Fig. 4-32, pp