DEEP SEA - AN UNTAPPED ZONE

1. FEATURES OF SEAFLOORFEATURES OF SEAFLOOR
§§ The discovery of mid-oceanThe discovery of mid-ocean
ridge system and the idea ofridge system and the idea of
convection cells in theconvection cells in the
asthenosphere led toasthenosphere led to
seafloor spreadingseafloor spreading asas
the mechanism forthe mechanism for
continental drift. The conceptcontinental drift. The concept
ofof continental driftcontinental drift andand
the theory of seafloorthe theory of seafloor
spreading combined tospreading combined to
produce plate tectonics,produce plate tectonics,
which propose thatwhich propose that thethe
plates are made up ofplates are made up of
continental and oceaniccontinental and oceanic
lithosphere bounded bylithosphere bounded by
ridges, trenches and faults.ridges, trenches and faults.

2. MORPHOLOGY OF PLANETMORPHOLOGY OF PLANET
EARTHEARTH
Pangaea was the only super continent of 200 million years ago

3. MORPHOLOGY OF PLANETMORPHOLOGY OF PLANET
EARTHEARTH
Laurasia = The northern portion of Pangaea composed of North America and Eurasia

4. MORPHOLOGY OF PLANETMORPHOLOGY OF PLANET
EARTHEARTH
Gondwanaland = The southern portion of Pangaea consisting of Africa, South
America, India, Australia and Antarctica

5. MORPHOLOGY OF PLANETMORPHOLOGY OF PLANET
EARTHEARTH

6. MORPHOLOGY OF PLANETMORPHOLOGY OF PLANET
EARTHEARTH

7. REASON BEHING CHANGINGREASON BEHING CHANGING
MORPHOLOGY OF THEMORPHOLOGY OF THE
EARTHEARTH

8. GRADUAL CRACK INITIATED

9. Ocean basinOcean basin
Continental margin Continental rise Ocean basin floorContinental margin Continental rise Ocean basin floor
Continental ContinentalContinental Continental
shelf slopeshelf slope
Abyssal Oceanic Sea mounts TrenchesAbyssal Oceanic Sea mounts Trenches
plains risesplains rises

10. Continental margin (Shelf + Slope)Continental margin (Shelf + Slope)
§§ The continental margin includes the continental shelf andThe continental margin includes the continental shelf and
slope. Theslope. The continental shelvescontinental shelves fringe the continents andfringe the continents and
slope gently towards the ocean basins. They are relativelyslope gently towards the ocean basins. They are relatively
flat, generally less than 130 m deep. However, the rangeflat, generally less than 130 m deep. However, the range
of the depth for the continental shelf is 30 m to aboutof the depth for the continental shelf is 30 m to about
275 m. The criterion for defining the seaward edge of the275 m. The criterion for defining the seaward edge of the
continental shelf is a marked change in slope. Thecontinental shelf is a marked change in slope. The
continental shelf has a gradient of about 1:1000.continental shelf has a gradient of about 1:1000.
§§ Seaward from the continental shelf is theSeaward from the continental shelf is the continentalcontinental
slopeslope, which extends to a depth of 1.6 to 3.2 Km. The, which extends to a depth of 1.6 to 3.2 Km. The
continental slope, has a gradient between 1:2 and 1:40.continental slope, has a gradient between 1:2 and 1:40.
Many submarine canyons scar the slope, which may be asMany submarine canyons scar the slope, which may be as
deep as 1200 m. It is believed that these canyons havedeep as 1200 m. It is believed that these canyons have
been cut by turbidity current of dense sediment–ladenbeen cut by turbidity current of dense sediment–laden
waters flowing down the surface of the continental slope.waters flowing down the surface of the continental slope.

11. Continental riseContinental rise
§§ Sediments from the continental shelf areSediments from the continental shelf are
carried into the deep ocean through thecarried into the deep ocean through the
canyons present in the continental slope. Atcanyons present in the continental slope. At
the foot of the continental slope, thethe foot of the continental slope, the
suspended materials and sediments settlesuspended materials and sediments settle
out, that slope gently towards the oceanout, that slope gently towards the ocean
floor. This region is called thefloor. This region is called the continentalcontinental
rise and has a gradient between 1:50 torise and has a gradient between 1:50 to
1:8001:800. The continental rise is fairly well. The continental rise is fairly well
developed in the Atlantic and Indiandeveloped in the Atlantic and Indian
oceans, but is narrow or almost non-oceans, but is narrow or almost non-
existent in the Pacific Ocean.existent in the Pacific Ocean.

12. Ocean basin floorOcean basin floor
§§ The ocean basin floor extends seaward fromThe ocean basin floor extends seaward from
the continental rise or the continentalthe continental rise or the continental
margins and includes the abyssal plains,margins and includes the abyssal plains,
oceanic rises, seamounts and trenches.oceanic rises, seamounts and trenches.

13. Abyssal plainAbyssal plain
§§ Abyssal plainsAbyssal plains are found at the base ofare found at the base of
the continental rise and are relatively flatthe continental rise and are relatively flat
plains having a gradient less than 1:1000.plains having a gradient less than 1:1000.
They are formed due to even depositionThey are formed due to even deposition
of sediments from the continental riseof sediments from the continental rise
carried down by the turbidity currentscarried down by the turbidity currents..

14. Oceanic risesOceanic rises
§§ Oceanic rises refer to rather isolatedOceanic rises refer to rather isolated
areas, which are elevated above theareas, which are elevated above the
abyssal floor and are distributedabyssal floor and are distributed
sporadically on the ocean basin floor.sporadically on the ocean basin floor.
They may vary from low hills toThey may vary from low hills to
mountains as high as 1525 m. Themountains as high as 1525 m. The
example of Bermuda rise is veryexample of Bermuda rise is very
prominent in this context on which theprominent in this context on which the
Bermuda Islands are formed.Bermuda Islands are formed.

15. SeamountsSeamounts
§§ SeamountsSeamounts are isolated peaks thatare isolated peaks that
rise several thousand meters aboverise several thousand meters above
the sea floor. They are volcanic inthe sea floor. They are volcanic in
origin and are found principally in theorigin and are found principally in the
vicinity of the fault zones.vicinity of the fault zones.

16. TRENCHESTRENCHES
§§ TrenchesTrenches are long narrow depressions in theare long narrow depressions in the
ocean floor that are over 6100 m deep. Theocean floor that are over 6100 m deep. The
deepest known trench in the oceandeepest known trench in the ocean
compartment is thecompartment is the Mariana trenchMariana trench of theof the
western North Pacific that is about 11,000 mwestern North Pacific that is about 11,000 m
deep. Trenches are invariably associated withdeep. Trenches are invariably associated with
the systems of active volcanoes, and arethe systems of active volcanoes, and are
believed to be caused by down wrapping of thebelieved to be caused by down wrapping of the
oceanic crust beneath the continental crust.oceanic crust beneath the continental crust.

17. DO LIFE EXISTS IN DEEPDO LIFE EXISTS IN DEEP
OCEAN?OCEAN?
§§ Yes – peculiar hydrothermal vent basedYes – peculiar hydrothermal vent based
biotic communities exist in the deep sea,biotic communities exist in the deep sea,
but the species diversity is extremelybut the species diversity is extremely
poor and food chain members are low.poor and food chain members are low.

18. BIODIVERSITY OF DEEPBIODIVERSITY OF DEEP
OCEAN FLOOROCEAN FLOOR
§§ Despite the extremes of temperature and pressure, these self-containedDespite the extremes of temperature and pressure, these self-contained
communities are some of the most productive in the sea and stand as thecommunities are some of the most productive in the sea and stand as the
proof of dependence of biotic community on non-conventional energyproof of dependence of biotic community on non-conventional energy
source. Chemosynthesis forms the foundation of such community andsource. Chemosynthesis forms the foundation of such community and
chemosynthetic bacteria occupy the first tropic level. Few common fauna ofchemosynthetic bacteria occupy the first tropic level. Few common fauna of
the hydrothermal vent community are listed here:the hydrothermal vent community are listed here:
§§ Giant white clamsGiant white clams – Calyotogena magnifica– Calyotogena magnifica
§§ MusselsMussels - Bathymodiolus thermophilus- Bathymodiolus thermophilus
§§ Tube wormTube worm -- Riftia pachyptilaRiftia pachyptila
§§ Galatheid crabGalatheid crab -- MunidopsisMunidopsis sp.sp.
§§ Enteropneust wormEnteropneust worm - Saxipendium coronatum- Saxipendium coronatum
§§ Brachyuran crabBrachyuran crab - Bythograea thermydron- Bythograea thermydron
§§ Turrid gastropodTurrid gastropod -- PhymorphynchusPhymorphynchus sp.sp.

19. §§ New lithosphere is formed at the ridges, or spreading centres;New lithosphere is formed at the ridges, or spreading centres;
old lithospheric material descends into trenches at subductionold lithospheric material descends into trenches at subduction
zones.zones.
§§ Evidence for lithospheric motion includes the match of theEvidence for lithospheric motion includes the match of the
earthquake zones to spreading centres and subduction zones,earthquake zones to spreading centres and subduction zones,
greater crustal heat flow near ridges, age measurement ofgreater crustal heat flow near ridges, age measurement of
seafloor rocks, age and thickness measurements of sedimentseafloor rocks, age and thickness measurements of sediment
from deep sea cores and the magnetic stripes in the seafloorfrom deep sea cores and the magnetic stripes in the seafloor
basalt on either side of the ridge system.basalt on either side of the ridge system.

20. THANK YOU