Submarine canyons

Topic of the lesson
Giant Submarine Canyons
Submarine CanyonsSubmarine Canyons
By
Prof.A. Balasubramanian
Centre for Advanced Studies in Earth Science
University of Mysore, India

 After attending this lesson, the user would be able to
understand the basic characteristics of the submarine
canyons, their origin, and their distribution in various
major oceans of the world.
 Detailed information about the morphological
conditions, sedimentology and marine life of the
submarine canyons will also be understood.
Objectives

 The surface beneath the oceanic waters is characterized
by a lot of relief features.
 On the basis of bathymetric surveys and detailed
oceanographic explorations, the morphology of ocean
floors was studied by several workers.
 The morphology of the ocean floor is highly uneven and
unique. The structure and distribution of relief features
of the ocean floors vary from place to place.
Introduction
(…Contd)

 Seas and oceans border the continents with two distinct
regions. One is the Continental margin and the other
one is the Deep Ocean basin.
 The Continental margin includes the gently sloping
Continental shelf & the rapid sloping, Continental slope.
 The sediments transported by the major rivers of
continents are deposited inside the seas, by forming
underwater channels and canyons.
Introduction
(…Contd)

 They are called as the submarine canyons.
 Submarine canyons are identified based on their
properties and their proximities to the coastal
environments, including the deep sea deposits.
 This lesson highlights about all these typical
underwater features.
Introduction

 The term canyon refers to a long, narrow and deep
valley of a major river.
 As the name implies, submarine canyons are deep
valleys extending inside the oceans.
 They intrude through both continental shelf and
continental slope and deposit their sediment loads
ultimately in the continental rises.
Submarine Canyons
(…Contd)

 The mouths of the canyons are normally open onto
features called as depositional fans.
 There are hundreds of submarine canyons
distributed in all the oceans and major seas of the
globe.
Submarine Canyons

Work of Shepard
 The characteristics of submarine canyons were
presented by Shepard in 1963.
 After a thorough analysis of global submarine
canyons, he distinguished the submarine canyons
from the channels that are formed through their
seaward extension.
(…Contd)

 Canyons that are cut into shelf and slope bedrock
and sediment, typically have a V-shaped profile, and
have a steeper gradient than the channels formed in
the depositional areas associated with the canyons.
 The Canyons lack levee morphology.
 Shepard, in 1973, distinguished the delta-front
troughs, which are “closely related to submarine
canyons”.
Work of Shepard

 Every submarine canyon has a canyon head, slopping
canyon walls, canyon width and length, observable
flow channels, canyon floor and a plain containing
sediments.
 The mouth of a canyon normally opens onto a
depositional fan.
 Every fan has an apex and a crest.
Parts of a Submarine Canyon
(…Contd)

 The canyon head occurs at the shelf break regions, in
approximately about 170 m water depth.
 All submarine canyons possess their own rims and
tributary valleys.
 They also differ in their dimensions.
 In comparison to modern canyons, dimensions of
ancient canyons are considerably smaller.
Parts of a Submarine Canyon

 Submarine canyons vary considerably in their
dimensions.
 Their length, valley walls and cross sectional profiles
are highly heterogeneous.
 The Bering Canyon is more than 1100 kilometersm
long and is the world's longest submarine canyon.
 The shortest canyons are those off the Hawaiian
Islands.
Physical Dimensions
(…Contd)

 The average length here is about 10 km.
 The average length of all the canyons has been
estimated to be around 55 km.
 The deepest canyon cuts nearly 5 km into the
continental slope regions as seen in the Grand
Bahama Canyon.
Physical Dimensions

Profile of the Canyons
 Submarine canyons are characterized by relatively
steep gradients.
 The average slope of canyon walls is 58 m/km.
 In general, shorter canyons tend to have higher
gradients.
 For example, shorter canyons of the Hawaiian group
have an average gradient of 144 m/km, whereas the
Bering Canyon has a slope of only 7.9 m/km.
(…Contd)

 The longitudinal and transverse sections vary from
canyon to canyon as well.
 Modern canyons are relatively narrow, deeply incised,
steeply walled, often sinuous valleys with
predominantly V-shaped cross sections.
Profile of the Canyons

 Many submarine canyons are found to be the
extensions of large rivers inside the sea.
 Some submarine canyons do not have any such
association with the rivers but they are associated
with some faults.
Extension of River channels
(…Contd)

 Canyons cutting across the continental slopes are
found at depths greater than 2 km below the sea level.
 Many submarine canyons continue to be the
underwater channels across the continental rise and
may extend for several hundred kilometers, inside the
slope.
Extension of River channels

 Submarine canyons are sites of considerable
geological complexity and biological diversity.
 They are developed due to various tectonic phases
including subsidence and rapid seafloor spreading.
Geomorphic setting
(…Contd)

 The geomorphology and extent of the canyons are
normally studied and mapped with high resolution‐
bathymetric data.
 Most of them are structurally controlled, with their
orientation mainly influenced by original rift
structures.
Geomorphic setting

Formation of Submarine Canyons
 Several theories have been proposed for the origin of
submarine canyons.
 The first theory is related to the down cutting action of
major rivers beyond shelf and slope regions of the oceans.
 Submarine canyons are valleys eroded by rivers, when full
glacial accumulation on land happened with lowering of
sea levels.
 This theory failed to say, why they are in further down the
slopes, deep inside the oceans.
(…Contd)

 Geologists believed that the submarine canyons are
formed due to turbidity currents.
 The role played by turbidity currents in creating the
deep valleys has been explained with evidences.
(…Contd)

 Turbidity currents are created when loose, wet
sediment tumbles down the slope like a submarine
landslide.
 Sliding might have been triggered due to
earthquakes or due to gravity on slopes when
there is overload of sediments.

 The major mechanism of canyon erosion is now
thought to be of turbidity currents and the
underwater landslides.
 A turbidity current is a current of rapidly moving,
sediment-laden water moving down a slope.
 A turbidity current can reach a speed of more than
100 km per hour and a distance of about 700 km.
Role of Turbidity Currents
(…Contd)

 A Turbidity current has tremendous erosive power
due to the mixture of water and sediments.
 It can create cracks, deepen them and form canyons.
 It will slow down when it reaches the sea floor.
 All the sediments brought by the submarine canyons
are deposited on the deep-ocean floors.
Role of Turbidity Currents

 The first global review on canyon distribution, origin,
geology and sedimentation patterns dates from 1966
made by Shepard and Dill who mapped 96 major
canyons around the world.
 High-resolution bathymetric data indicate that there
are well over 660 submarine canyons distributed
globally.
Global distribution
(…Contd)

 The very recent tabulation, based on satellite altimetry,
suggests that the number of submarine canyons could
exceed 5800.
 The patterns of benthic community structure and
productivity have been studied only in a small number
of submarine canyons.
 It is less than 45. It is less than 0.7%.
Global distribution

 Whenever, any attempt is made to investigate the
submarine canyons, an integrated approach is adopted
to explore the underwater features and processes.
 This requires a thorough analysis of various
oceanographic aspects.
 The regional geology of the oceans is to be studied first.
 Then, the ocean geomorphology is to be explored
through bathymetric surveys.
Integrated analysis
(…Contd)

 Monitoring of bathymetric, hydrological,
climatological and biological parameters are done
during deep water explorations.
 The underwater sediments and life are to be analyzed
after understanding the ocean dynamics, including the
nature of water circulation.
Integrated analysis

 Oceanographic Surveys are conducted with very clear
objectives.
 It requires sophisticated equipment & experienced
scientific personnel, including the crew of the vessels.
 For understanding the nature of geomorphology and
sedimentology, various geophysical methods are to be
adopted.
Oceanographic Surveys
(…Contd)

 Real-time data acquisition and processing are done in
many cases.
 Side Scan Sonar soundings, Multi-beam Sonar
soundings (Swath) and Shallow Seismic Reflection
surveys are conducted over the continental shelf,
slope and rise regions.
 The data of wind induced waves, tides and ocean
currents are also analysed simultaneously.
Oceanographic Surveys

 The basin geology is to be studied with all the data and
samples collected from the oceans as water, sediment,
and biota.
 It is necessary to collect samples of planktons, nektons
and benthos.
 Bathymetric charts, seismic profiles, sediment
traverses and biotic zonation mapping are done, in
order to understand the physical, biological, chemical
and geological oceanography of submarine canyons.
Basin geology

Sedimentology
 For understanding the sedimentology of underwater
features, collection and analysis of sediment samples
are done with Sediment Sampling tools.
 Water samples are also collected at regular intervals of
space and depth, to determine the temperature,
density, salinity and other properties.
 Still Camera photography is made to record all
features.

 Submarine canyons serve as major conduits for
transporting sediment from land, then from land to
the shelf and from the shelf to the slopes.
 Underwater canyons are the prominent erosional
features found both in the U.S. Pacific and Atlantic
continental margins.
Erosional features
(…Contd)

 There also exists a distinction between the
submarine canyons and the submarine erosional
channels.
 The channels have no connection with the shelf or
land based rivers.
Erosional features

 Canyons and channels are associated with gullies, troughs,
fault valleys, and sea valleys.
 River sediment, nutrients and organic matter are directly
moved down through the submarine canyons.
 They are also subjected to more regular and vigorous
sedimentary processes involving not only terrigenous
sediment, but also nutrients and organic matter.
As Conduits for sediment transport
(…Contd)

 Submarine canyons are the most important conduits
for funneling sediment from continents to oceans.
 They are the zones of sediment bypassing.
 Very little sediment accumulates within the canyon,
until it ceases to be an active conduit.
As Conduits for sediment transport

 There are two main types of submarine canyons
observed over the globe.
 The first types of canyons extend from the
continental shelf to the slope.
 Often these canyons are located in close proximity
to the present-day river systems.
 River sediment, nutrients and organic matter are
directly deposited into this type of submarine
canyons.
Classification

Blind Canyons
 The second and most common type of submarine
canyon is the one which is separated from the
continental shelf.
 The canyon head is located on the upper continental
slope regions, in water depths of a few hundred to
few thousand metres.
(…Contd)

 These canyons are known as ‘blind canyons’.
 They do not necessarily occur adjacent to any major
rivers.
 They are less likely to intercept the continental shelf
zones and do not posses any river derived sediments‐
or nutrients or organic matter.
Blind Canyons

 On the basis of morphogenetic processes, submarine
canyons are classified into two different types as
Glacially eroded Canyons and Non-glacial Canyons.
 The non-glacial submarine canyons are more in
number than the glacial types in the oceans.
 These are also widely spread over in all the oceans.
Types of Canyons
(…Contd)

 Most of them are located in front of the mouths of the
major rivers.
 The longitudinal course of Submarine Canyons is usually
sinuous.
 The gradient of submarine canyons are steeper than the
continental canyons.
 Most of them are several Km wide at their heads and
their average length may be about 10 to 16 Km.
Types of Canyons

 The term Mass wasting is used to denote the slow
movement of earth’s surface masses, under the action
of gravity.
 It happens to all the underwater masses.
 It would also include the effects of bioerosion and
sand migration.
Role of mass movements
(…Contd)

 Submarine canyons are expected to experience
both slope failures and wall collapses.
 The processes like mass wasting, slumping, and
submarine landslides are the causative factors for
slope failures in the submarine canyons.
Role of mass movements

Why to study these features?
 The major significance of studying the submarine
canyons is to understand the deep-sea habitats.
 Submarine canyons are known for their support to a
diverse range of biological communities surviving
within its nutrient-rich water masses.
(…Contd)

Why to study these features?
 The steep sides of exposed lithified strata provide the
hard surface for the sessile organisms to survive and
the flat, sediment-laden floors support the burrowing
organisms to survive.
 In addition, the submarine canyons are potential
zones for a lot of physical and biological processes
inside the oceanic water masses.

 Canyons can be complex topographic features often
characterized by complicated patterns of hydrography, flow, and
sediment transport and accumulation.
 The unusual physical oceanographic conditions, inside canyons,
can be caused by topographic effects such as accelerated
currents and dense-water cascades, which increase suspended
particulate concentrations and transport organic matter from
coastal zones to deeper regions of the margin.
 These phenomena can be responsible for enhancing both pelagic
and benthic productivity inside canyon habitats as well as the
biodiversity of many benthic faunal groups.
Complex processes

 Because of the physical complexity of canyon habitats,
predictions concerning the effects of canyons on local
and regional diversity are not straightforward.
 Since a variety environmental and physical characteristics
like topography, current regime, sediment availability,
and quantity and quality of organic matter supply are
involved, it would be very difficult to predict the nature
of canyon habitats.
Unpredictable zones

 The foremost important driver, that is affecting the
biodiversity and biomass-abundance -patterns in
canyons, is the organic matter input with reference
to the sources, quantity and quality.
 This is also related to the coastal detrital inputs like
kelp and other macrophytic debris.
Drivers of biological productivity
(…Contd)

 Finally, it is related to the pelagic productivity regimes
like upwelling, meso-scale eddies, and zooplankton
aggregations.
 Seafloor terrain and substrate heterogeneity
altogether account for the second most important
driver of benthic biodiversity in submarine canyons.
Drivers of biological productivity

Super parameters
 The physical canyon structure such as bottom types
and sedimentary structure, presence of hard
substrates, grain size distributions, shape and relief of
the canyon are the geological factors of canyons.
 One of these factors, sediment grain size, can be
considered as a ‘super-parameter’ since it directly or
indirectly reflects local physical energy and
sedimentation patterns.

 Continental margins are considered major reservoirs
of marine biodiversity when compared to the most
diverse terrestrial and shallow water marine habitats.
 Submarine canyons are an important source of
nutrients and sediments for the deep ocean marine
life.
Hot spots for biological production
(…Contd)

 Submarine canyons are also major hotspots of
biological production and fish catch.
 Scientists found abundant life, in many of these
channels, from their rims down to the bottoms of
their steep cliffs.
 The biological abundance may be due to the inflow
of nutrients from the rivers that feed these canyons.
Hot spots for biological production

 The majority of findings suggest that enhanced habitat
heterogeneity and organic matter deposition in canyons
are responsible for enhancing benthic biodiversity and
creating biomass hotspots.
 Enhanced local fishery production in canyons, when
contrasted to regular slope environments, has also been
reported and attributed to a ‘canyon effect’.
Canyon effects
(…Contd)

 The channelling and concentrating of detrital organic
matter and pelagic animal populations in canyons are very
interesting subjects of study.
 Many other unusual ecological characteristics have been
attributed to canyons such as
a) concentrating on vertical migrators,
b) displacing deepwater species to coastal zones,
c) Promoting topographically induced upwelling and
enhancing diapycnal mixing via internal wave generation.
Canyon effects

 A 'v' shaped canyon is usually associated with high-
energy currents, sediment slumps that can exposure
hard substrates enhancing habitat heterogeneity and
favouring mobile and sessile mega-fauna suspension
feeders.
 On the other hand, it can promote sediment
scouring by disturbing the macro-fauna.
Valley Shape and substrate
(…Contd)

 The u-shaped canyons affect the sediment deposition and
can potentially be a proxy of organic enrichment. For
example, fine organics can deposit in 'u' shaped wider and
with gentle sloping walls and flat thalweg enhancing food
availability.
 Homogeneous conditions prevent 3-dimensional habitat
structuring but allows organic matter retention.
 The mosaic type habitats (soft mixed with hard substrates)
favors niche partitioning and increased.
Valley Shape and substrate

Habitats
 The enormous reservoir of biodiversity on continental
margins promote many margin habitat types. The typical
types are cold seeps, coral mounds, foraminifera beds,
oxygen minimum zones and open slopes.
 A recent study estimates that the total marine eukaryotic
biodiversity is around 2.2 million species.
 A decadal effort made by the international project
Census of Marine Life (CMOL) collected 6,000 potential
new species, and completed new descriptions of 1,200
species.

 Sediment type, substrate inclination, water-mass
properties like temperature and dissolved oxygen, and
organic matter input, all control the biomass in canyons.
 While organic detrital input and habitat heterogeneity
can lead to differences in benthic communities between
canyons and slopes, a variety of other environmental
factors can also influence these patterns.
Environmental factors
(…Contd)

They are
1. the frequency and intensity of disturbance such as flushing events
2. sediment slumps at the base of canyon walls
3. water mass properties such as temperature variability and
oxygen concentrations and
4. the vertical flux of particulate organic carbon (POC).
 All these factors can differ between canyons and open slopes.
 A number of environmental variables, including temperature,
dissolved oxygen, organic detritus occurrence, and the estimated
POC flux, all vary with depth.
Environmental factors

While analysing the biodiversity of submarine canyons, the
following data are needed.
A.Water mass variability characteristics including
Temperature, dissolved oxygen and Salinity.
B.Organic matter input including Particulate organic carbon
(POC) flux at the seafloor, Percent occurrence of
terrestrial plant and macroalgae detritus on the seafloor,
plant detritus like leaves, trunks& seeds.
Research data requirements
(…Contd)

C. Sediment particle characteristics.
D. Seafloor terrain characteristics including bathymetry and
backscatter reflectivity to decipher the Basins, Watershed,
and Flow Direction- finding the network of streams and
rivers, canyon transverse-profile, sloping along the profile
and
E. Abundance patterns and organic matter input, Community
structure patterns and environmental drivers.
Research data requirements

 High sediment loading is observed in shelf-incising
canyons providing large and steady supplies of
sediments that reach the canyon heads and are
transported down the canyon.
 High sedimentation is often associated with high
organic content.
Sediments of Canyons
(…Contd)

 Submarine fans and related turbidite systems comprise
deposits of mass movements, including slides, slumps,
turbidity currents, and debris flows.
 Canyons can be sites of enhanced organic-matter flux
and sediment deposition.
Sediments of Canyons

 Submarine fans are accumulations of sediment
deposited at the terminal end of land-to-deep-sea
sediment-routing systems.
 At a given moment in time, sediment-routing systems
comprise sediment source areas dominated by
denudation, a zone of sediment transfer, and a terminal
region of deposition, such as a submarine fan.
Deep sea fans
(…Contd)

 These are shallow marine sediments.
 They are fan- or cone-shaped systems.
 They are located off the seaward opening of large
rivers and submarine canyons.
Deep sea fans

 Submarine Canyons exist in almost all the three major
oceans.
 The largest submarine canyons are located in the Pacific
Ocean and Atlantic Oceans.
 The undersea canyons and seamounts of the major
oceans are home to an extraordinary universe of life,
from rare coldwater corals, anemones and sponges, to
an array of fish and marine mammal species, including the
endangered sperm whale.
Canyons in world’s major oceans
(…Contd)

 The continental slope of New England and the Mid-
Atlantic holds approximately 70 canyons of varying
shapes and sizes.
 Many submarine canyons have yet to be fully
explored.
Canyons in world’s major oceans

Canyons of the Pacific Ocean
 The following are the submarine canyons of the Pacific
Ocean:
 Bering Canyon
 Monterey Canyon
 Navarin Canyon
 Pribilof Canyon
 Scripps Canyon
 Zhemchug Canyon

 Three of the largest submarine canyons in the world
are incised into the Beringian (North American)
margin of the Bering Sea.
 The Bering Canyon, which is farther south in the
Bering Sea, is first in length and total area.
 In contrast, the largest submarine fans—e.g., Bengal,
Indus, and Amazon—have substantially smaller, delta-
front submarine canyons that feed them.
The Bering Canyon
(…Contd)

 The Bering Canyon is the longest of the Bering Sea
canyons.
 It extends to about 400 km across the Bering shelf and
slope.
 It is confined at its eastern edge by the Aleutian Islands.
 The width of the canyon at the shelf break is about
65 km.
The Bering Canyon
(…Contd)

 It is about two-third in dimension than that of the
Zhemchug Canyon and Navarin Canyons.
 Due to its great length, the Bering Canyon has the
largest area.
 At a depth of 3200 m, the Bering Canyon reaches
the Aleutian Basin.
The Bering Canyon

 The Monterey Canyon is the largest and deepest
submarine canyon off the Pacific Coast of North
America. The canyon has three tributaries at its upper
reaches in Monterey Bay, near California. They are:
 Minor Soquel canyon to the north
 Main Monterey Canyon, with its head aligned east-west
off Moss Landing
 Carmel Canyon to the south.
Monterey CanyonMonterey Canyon
(…Contd)

 Carmel canyon is the main tributary.
 It joins with the main canyon at an axial depth of
1800m.
 The sinuous courses of Monterey canyon goes upto
2900m.
Monterey CanyonMonterey Canyon

 The Navarin Canyon is a submarine canyon in the
Bering Sea.
 It is just as wide but less than half as deep as the
Zhemchug Canyon, which is the largest canyon in the
world.
 The Navarin Canyon is the third-largest to cut
through the Beringian margin.
The Navarin Canyon
(…Contd)

 It is the second-largest in area.
 Though these canyons were not directly formed by
rivers, it is postulated that when the sea level was low
during the Ice Ages, rivers such as the Yukon and the
Kuskokwim may have shaped in part the heads of these
canyons.
 At the shelf break, it is approximately 100 kilometres
(62 mi) wide.
The Navarin Canyon

 Pribilof is a long submarine canyon rising from the Bering
Abyssal plain on the floor of the Bering Sea.
 It is located southeast of the Pribilof Islands, near Alaska.
 It runs across the edge of continental slope and is 426 km
long with walls 1800 m high.
 It is believed to have been formed when large masses of
sediments supplied by Alaskan and Siberian rivers slumped
down the slope of the shelf region.
Pribilof Canyon

 Scripps Canyon is a shallow marine canyon in the
Pacific off La Jolla, in California.
 The valleys are 12m deep.
 The maximum depth goes upto 300m.
 Due to its shallowness and closer to the Scripps
Institution of Oceanography, it has been thoroughly
studied.
Scripps Canyon

 Zhemchug Canyon is a giant underwater canyon located
in the middle of the Bering Sea.
 This submarine canyon is the largest canyon in the
ocean.
 The canyon has a vertical relief of 2600 meters dropping
from the shallow shelf the Bering Sea to the depths of
the Aleutian Basin.
 Zhemchug Canyon is deeper than the Grand Canyon.
Zhemchug Canyon
(…Contd)

 Zhemchug Canyon has two main branches, each larger than
typical continental margin canyons such as the Monterey
Canyon.
 Zhemchug Canyon is the largest submarine canyon in the
world, based on drainage area (11,350 km2
) and volume
(5800 km3
).
 Zhemchug Canyon is important habitat for many species of
ocean wildlife. What makes the Zhemchug Canyon the
largest canyon in the world is, not only its great depth, but
its large cross-sectional area.
Zhemchug Canyon
(…Contd)

The Atlantic Ocean has the following major submarine
canyons:
Amazon canyon
Hudson canyon
Veracruz Canyon.
Congo Canyon
Great Bahama Canyon.
Canyons of the Atlantic Ocean
(…Contd)

 More than 200 species of invertebrates have been
identified in the Atlantic submarine canyons and
seamounts, including dozens of species of stony
corals, black corals, soft corals, sea pens, anemones,
and sponges.
Canyons of the Atlantic Ocean

 The Amazon Canyon is a submarine canyon within the
Amazon Fan in the Atlantic Ocean.
 It is located approximately 322 km from the mouth of
the Amazon River, near South America.
 It covers an area of 2,250 square km.
 It was formed in the mid to late Miocene period.
The Amazon Canyon
(…Contd)

 The canyon is believed to have formed through mass
failures, and subsequently evolved through
underwater erosion.
 Because of its relatively small size, the canyon has
been extensively mapped.
The Amazon Canyon

 The Hudson canyon is another large submarine
canyon incised into the Atlantic Continental slope
and outer shelf off New York Harbour, U.S.A.
 It is extended from the Hudson River.
 The canyon is about 80 km long with its fan goes to a
depth of 3000 m.
The Hudson Canyon
(…Contd)

 It’s a conduit for moving sediments, nutrients, and
pollution from the land to the deep ocean.
 Hudson Canyon is a pathway from land to sea,
extending over 400 nautical miles seaward from the
New York/New Jersey harbor, across the continental
margin, and out to the deep ocean basin extending 300
miles beneath the sea.
The Hudson Canyon
(…Contd)

 The canyon was formed during the last Ice Age, over
10,000 years ago, when the sea level was about 121. 9 m
lower and the mouth of the Hudson River was near the
edge of the continental shelf, about 160.9 km east of its
present site.
 The river discharged sediment that helped carve the
canyon aided by underwater avalanches of mud and sand.
The Hudson Canyon

 The Veracruz Canyon is an underwater canyon
located off the eastern coast of Mexico in the Gulf
of Mexico not far from the port city of Veracruz.
 It is considered for drilling to obtain oil in and
around Veracruz Canyon.
The Veracruz Canyon

 Congo Canyon, a large submarine canyon incised into the
South Atlantic continental shelf and slope of equatorial
Africa.
 The head of the canyon lies 28km inland, up the Congo
Estuary.
 It has a depth of 21m.
 The canyon crosses the entire shelf for 85 km offshore.
 It cuts across the continental slope and goes upto a depth
of 2650 m.
Congo Canyon

 Great Bahama Canyon is located off the Bahamas, in
the Atlantic Ocean.
 It lies northeast of the Great Bahama between Great
Abaco and Eleuthera Islands.
 Two main branches merge to form the submarine
canyon.
 The vertical wall of the canyon goes upto 4285 m
from the canyon bed to the surrounding sea bed. It is
225 km in length.
Great Bahama Canyon
(…Contd)

 Submarine canyons resemble river canyons on land,
usually having steep, rocky walls.
 They are found along most continental slopes.
 Those of the Grand Bahama Canyon, which are thought
to be the deepest, cut nearly 5 km deep into the
continental slope.
 Most submarine canyons extend only about 50 km or
less, but a few are more than 300 km long.
Great Bahama Canyon

Canyons of the Indian Ocean
Indian Ocean has a few notable submarine canyons.
They include:
 The Perth Canyon and
 Swatch-of-No-Ground (SoNG).

 The Perth Canyon is a submarine canyon located on
the edge of the continental shelf off the coast of
Fremantle, Western Australia.
 It is located at approximately 22 kilometres west of
Rottnest Island.
The Perth CanyonThe Perth Canyon
(…Contd)

 It was carved by the Swan River, probably before the
Tertiary, when this part of the continental shelf was
above sea level.
 It is an average of 1.5 kilometres deep and
15 kilometres across, making it similar in dimension
to the Grand Canyon.
(…Contd)

 The Perth Canyon occupies an area of 2,900 square
kilometres and ranges in depth from 700 to 4,000
metres.
 Within a few kilometers, its depth drops from
200 metres down to 1,000 metres, and then it continues
as a deep gully all the way out to the 4,000-metre depth.
 It contains the world’s largest plunge pool – a depression
in the canyon which is 2 kilometres long, 6 kilometres
across, and 300 metres deep.

 The Swatch-of-No-Ground (SoNG) is a submarine
canyon in the northern Indian Ocean.
 It supports a fairly well described group of fauna that
includes one of the world’s largest known
populations of Indo-Pacific bottlenose dolphins, a
possibly resident population of Bryde’s whales, and
large groups of spinner and pantropical spotted
dolphins.
The Swatch-of-No-Ground (SoNG)
(…Contd)

 The distribution of these species is stratified according
to environmental characteristics, with Bryde’s whales
and bottlenose dolphins concentrated in relatively
shallow waters close to the canyon head where
upwelling is maximized.
The Swatch-of-No-Ground (SoNG)

Methane gas
 Submarine canyons are believed to contain vast
reserves of methane hydrates, a promising clean-
burning natural energy source believed to reside in
near freezing temperatures under high pressures
within sea floor sediments, although no technology
yet exists to extract the methane.
(…Contd)

 These methane deposits are dispersed under the
ocean floor over millions of square miles in this
and other areas of the world.
 Some scientists speculate that the methane gas
pockets in the underwater shelves could cause
undersea landslides that might produce tsunamis.
Methane gas

Marine life in Canyons
 The interplay of physical and biological processes is
common in submarine canyons.
 The very dominant ones are mass wasting, turbidity
currents, bottom currents, and bioerosion.
 Submarine Canyons support a fairly well described
group of fauna that includes one of the world’s
largest known populations.
(…Contd)

Marine life in Canyons
 The distribution of these species is stratified
according to environmental characteristics.
 Submarine canyons are geologically significant,
oceanographically important underwater features.

 Continental margin is facing increasing threats from
human activities such as bottom fishing, oil and gas
extraction, and sewage dumping.
 Many of them are anthropogenic influences penetrating
into the deep sea.
 They’re also a major sources of pollution.
Coastal hazards
(…Contd)

 Marine pollution occurs when harmful, or potentially
harmful, effects result from the entry into the ocean
in the form of chemicals, particles, industrial
effluents, agricultural chemicals and residential
wastes, or the spread of invasive organisms.
Coastal hazards

 Submarine canyons are dramatic and widespread
topographic features crossing continental and island
margins in all oceans.
 Submarine canyons have long been a subject of great
interest to marine geologists and oceanographers.
 Seafloor terrain and substrate heterogeneity
altogether account for the second most important
driver of benthic biodiversity in submarine canyons.
(…Contd)
Conclusion

Conclusion
 The physical canyon structure such as bottom types and
sedimentary structure, presence of hard substrates, grain
size distributions, shape and relief of the canyon, has a
great influence on marine life.
 Despite their unusual ecological characteristics and
global distribution along oceanic continental margins,
only scattered information is available about the
influence of submarine canyons on deep-sea ecosystem,
its structure and productivity. Submarine canyons are
very typical features in the ocean floors.

Submarine canyons

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