key points 1. the ocean floor is mapped by bathymetry. 2. ocean-floor topography varies with...
TRANSCRIPT
![Page 1: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/1.jpg)
Key Points
1. The ocean floor is mapped by bathymetry.
2. Ocean-floor topography varies with location.
3. Continental margins are “active” or “passive”.
4. The topography of deep-ocean basins differs from that of the continental margin.
![Page 2: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/2.jpg)
Posidonius • conducted the first bathymetric studies• 85 B.C.
http://www-groups.mcs.st-and.ac.uk/history/BigPictures/Posidonius.jpeg
2 km
Bathymetry = study of ocean floor contours
The early, simplest methods involved lowering a weight on a line.
![Page 3: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/3.jpg)
HMS Challenger
(1872-1876)• made the first
systematic attempt to chart the basins of the world ocean
• made 492 bottom
soundings confirmed the discovery of the Mid-Atlantic Ridge
![Page 4: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/4.jpg)
http://en.wikipedia.org/wiki/Reginald_Fessenden
Reginald Fessenden (1866-1932)• Canadian inventor• in 1914, developed a
type of sonar system for locating icebergs
“Iceberg Detector and Echo Depth Sounder”
![Page 5: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/5.jpg)
http://en.wikipedia.org/wiki/Reginald_Fessenden
Reginald Fessenden (1866-1932)• Canadian inventor• in 1914, developed a
type of sonar system for locating icebergs
“Iceberg Detector and Echo Depth Sounder”
![Page 6: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/6.jpg)
V = speed of sound in water(about 1.5 km/sec)T = time
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.
![Page 7: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/7.jpg)
During World War I (1914-1918)• used to detect enemy
submarines
http://www.eastlanddisaster.org/uc97.jpg
Meteor expedition (1925-1927)• used to study the seabed
http://oceanworld.tamu.edu/resources/ocng_textbook/chapter02/Images/Fig2-2s.jpg
![Page 8: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/8.jpg)
World Ocean Floor
![Page 9: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/9.jpg)
http://www.panorama-map.com/Europeans/Berann/berannpacificocean500.html
Pacific Ocean
![Page 10: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/10.jpg)
Two new techniques improved studies of the seafloor:
1) multibeam echo sounders
2) satellite altimetry
![Page 11: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/11.jpg)
Multibeam systems combine many echo sounders.
• up to 121 beams• signal sent every 10 secs <200 research vessels are
equipped with multibeam systems
![Page 12: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/12.jpg)
Seabed contours can be mapped using satellites.
Satellites cannot measure ocean depths directly• but, they can measure sea surface height
![Page 13: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/13.jpg)
Sea surface
Seafloor
![Page 14: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/14.jpg)
?Sea surface
Seafloor
![Page 15: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/15.jpg)
Gravitational attraction “pulls” water
Over a 2000 m seamount, water rises about 2 m
Seafloor
Sea surface
![Page 16: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/16.jpg)
http://www.ngdc.noaa.gov/mgg/image/global_grav_large.gif
Mapped by: Geosat, TOPEX/Poseidon, and Jason-1
Seafloor topography inferred from sea surface height measurements
![Page 17: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/17.jpg)
Oceans can be divided into two major provinces: 1) continental margin2) ocean basin (deep ocean floor – Basalt)
![Page 18: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/18.jpg)
• earthquakes• volcanic activity
Continental margins are “active” or “passive”.
Pacific-Type Atlantic-type
• no earthquakes• no volcanic activity
![Page 19: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/19.jpg)
Three main parts of the continental margin:1. Shelf 2. Slope 3. Rise
![Page 20: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/20.jpg)
Continental shelf: shallow submerged extension of a continent
• Average width: 1280 km (800 miles)
• Granitic rock covered by sediments
• Methane compounds
![Page 21: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/21.jpg)
http://media.allrefer.com/s1/l/c0601400-continental-shelf.jpg
• up to 350 km
• most material comes from erosion of continent
![Page 22: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/22.jpg)
http://www.cryingvoice.com/Evolution/gifs/hydroNA.jpg
Atlantic
![Page 23: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/23.jpg)
active margin – often very narrow
passive margin – broad
The shelf width is usually determined by its proximity to a plate boundary.
![Page 24: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/24.jpg)
Continental shelves are greatly influenced by changes in sea level (Ice Ages)
Sea level rise
![Page 25: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/25.jpg)
http://whyfiles.org/shorties/202mass_extinct/images/land_bridge.gifBering Strait
![Page 26: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/26.jpg)
http://whyfiles.org/shorties/202mass_extinct/images/land_bridge.gifBering Strait
![Page 27: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/27.jpg)
http://whyfiles.org/shorties/202mass_extinct/images/land_bridge.gif
Allowed human migration 12,000 years ago
Bering Strait
![Page 28: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/28.jpg)
Continental slopes connect continental shelves to the deep-ocean floor
shelf break
![Page 29: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/29.jpg)
Submarine canyons form at the junction between continental shelf and continental slope. (Edge of ocean basins)
![Page 30: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/30.jpg)
http://www.tahoemaps.com/files/Monterey_large.jpg
Monterey Bay canyon
![Page 31: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/31.jpg)
http://www.marine-geo.org/gallery/images/MontereyBay3D.jpg
2000 m
Monterey Bay canyon
![Page 32: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/32.jpg)
How do submarine canyons form?
Submarine canyons cut into the continental shelf and slope, often terminating on the deep-sea floor in a fan-shaped wedge of sediment.
![Page 33: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/33.jpg)
![Page 34: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/34.jpg)
turbidity current
an underwater “avalanche” of sediment
http://unit.aist.go.jp/igg/rg/igi-rg/beta/sl-support/R-formation/TurbidityCurrent.jpg
Most geologists believe that submarine canyons have been formed by abrasive turbidity currents plunging down the canyons.
![Page 35: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/35.jpg)
Continental rises form as sediments accumulate at the base of the
continental slope
continental rise
• much sediment
• usually along passive margins
![Page 36: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/36.jpg)
The topology of deep-ocean basins differs from that of the continental margin
Deep-ocean basins comprise mainly:
1) oceanic ridge systems
2) sediment-covered plains
![Page 37: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/37.jpg)
Oceanic ridges circle the world
• underwater mountain ranges• stretch 65,000 km• often covered with little
sediment
![Page 38: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/38.jpg)
http://www.berann.com/panorama/archive/image/PN_W_10.jpg
Mid-Atlantic Ridge
![Page 39: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/39.jpg)
http://www.berann.com/panorama/archive/image/PN_W_10.jpg
Mid-Atlantic Ridge
transform faultsfracture zones
![Page 40: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/40.jpg)
Hydrothermal vents are hot springs on active oceanic ridges•350 degrees Celsius• discovered in 1977 by Robert Ballard and J. F. Grassle
Alvin
http://www.mbari.org/molecular/images/EPR%20mussel-map.jpg
![Page 41: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/41.jpg)
Alvin• can carry 3 people• can dive to 4000 m• 1964 – 2007• >4000 dives
manned submersible• 6,500 m
unmanned submersible• 11,000 m
![Page 42: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/42.jpg)
![Page 43: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/43.jpg)
http://www.csa.com/discoveryguides/vent/images/smoker.jpghttp://whyfiles.org/coolimages/images/csi/nur04506.jpg
“black smokers”
20 m
350oC
2,800 m depth
solutions exiting vents are acidic (pH = ~3.5) and contain up to 300 ppm hydrogen sulfide (H2S)
• a highly reduced molecule, so much energy can be obtained when it is oxidized
![Page 44: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/44.jpg)
hydrothermal vent community
http://www.sciencedaily.com/images/2005/02/050223124700.jpg
• includes snails, shrimps, crabs, tube worms, fishes
• depends on chemosynthetic bacteria for food
chemosynthesis Tube worms
deep-sea vent mussels
![Page 45: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/45.jpg)
Abyssal plains and abyssal hills cover most of Earth’s surface.
Abyssal hills• small sediment-covered
extinct volcanoes or rock
• > 200 m (650 ft)
Abyssal plains• 40% of the ocean floor• common in the Atlantic• rare in the Pacific• covered by sediment• cold
Flat
![Page 46: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/46.jpg)
Volcanic seamounts and guyots project above the seabed
• about 30,000• about 10,000 in the Pacific
http://upload.wikimedia.org/wikipedia/en/thumb/2/25/Seamount_Locations.png/350px-Seamount_Locations.png
• >1 km in height• important
fishing areas
Emperor Seamounts
seamount
![Page 47: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/47.jpg)
Guyot: flat-topped seamount that once reached the surface
http://en.wikipedia.org/wiki/Image:Guyot.jpg
![Page 48: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/48.jpg)
Trench: arc-shaped depression on the deep-ocean floor
• occur near subduction zones
• deepest places in the ocean
• most in the Pacifichttp://geology.com/records/ocean-trench.gif
![Page 49: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/49.jpg)
Peru-Chile trench
http://en.wikipedia.org/wiki/Image:Peru-Chile_trench.jpg
Puerto Rico trench
![Page 50: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/50.jpg)
Japan Trench10,595 m
Mariana Trench11,022 m
![Page 51: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/51.jpg)
Trieste
• reached the bottom of the Mariana Trench in 1960 – Challenger Deep
![Page 52: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/52.jpg)
Kaiko
• Japanese deep-sea submarine
• sampled bacteria from the bottom (10,897 m) of the Mariana Trench in 1996
![Page 53: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/53.jpg)
Sampling of the world's deepest sea sediment by "Kaiko" at the Mariana Trench, Challenger Deep
Bacteria collected from the Mariana Trench
![Page 54: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/54.jpg)
Nereus
![Page 55: Key Points 1. The ocean floor is mapped by bathymetry. 2. Ocean-floor topography varies with location. 3. Continental margins are “active” or “passive”](https://reader038.vdocument.in/reader038/viewer/2022110320/56649cb75503460f9497cda7/html5/thumbnails/55.jpg)
Key Points
1. The ocean floor is mapped by bathymetry.
2. Ocean-floor topography varies with location.
3. Continental margins are “active” or “passive”.
4. The topography of deep-ocean basins differs from that of the continental margin.