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Ocean Bottom
The Water Planet
Global ocean is consists of all the oceans
on the Earth
A sea is a smaller body of ocean water
that may be surrounded by land
Oceanography
Oceanography began when Matthew Maury
aboard the HMS Challenger explored the
oceans with limited technology from 18721876.
Today with modern technology ships like the
JOIDES Resolution and the CHIKYU, both drill
the ocean bottom finding out more about the
workings of plate tectonics and
sediment of the ocean.
Sonar
Sound Navigation and Ranging is a system
that uses sound to determine the depth and
features of the ocean bottom. Side scan
radar is used to map the bottom of the ocean
Under water Submersibles are used to
explore the depth, some with robots to collect
samples.
Continental slope is at the edge of
the continental shelf where the
sea floor may plunge steeply 4-5
kilometers
Marks the boundary between the
continental crust and the oceanic
crust
Continental rise is the area between the
continental slope and the ocean floor
It is made of sediments that wash down
from the continental shelf
Turbidity current carry large amounts of
these sediments in masses of moving
water, it is like an underwater avalanche
Submarine canyons are deep
V shaped valleys cut through
the continental shelf and
slope
Features of the Ocean Floor
Abyssal Plain
Large flat areas on the bottom of the ocean
Atlantic and Indian oceans have largest
abyssal plains because almost all the worlds
major rivers flow into them producing a large
amount of sediment deposits in the plains
Seamounts and Guyots
Seamounts are underwater volcanic mountains
They have steep sides and narrow summits
and rise more than 1000 meters above the sea
floor
When seamounts rise above the surface of the
ocean they become islands
Guyots are seamounts that do not rise to a
peak or have eroded tops
Mid-ocean Ridges
Largest mountain ranges on the
Earth
These are formed where the plates
are pulling apart
Rift valleys run along the middle of
the mid-ocean ridges
Trenches
The deepest part of the ocean found
along edges of sea floor
Long narrow crevices that can be 11,000
meters deep
Deepest trench is the Mariana Trench in
the Pacific Ocean that is more than
11,000 meters deep
Hydrothermal Vents
Openings into the mantle of the Earth
where sea water seeps down and
returns to the ocean
Reefs
Reefs are large masses and ridges of
limestone rocks produced by the shells
of animals
There are three types of coral reefs:
fringing reefs touch the shoreline of a
volcanic island
Coral Reefs (cont)
Barrier reefs that are separated from
the shore by an area of shallow water
called a lagoon
Coral Reefs (cont)
And an atoll that is a ring of coral reef
that surrounded an island that has been
worn away or sunk
Properties of Ocean Water
Ocean water is a
mixture of gases
and solids dissolved
in pure water
Oceanographers
believe that ocean
water contains all of
the natural elements
found on Earth
All but 5 have
been found
Gases in Ocean Water
Nitrogen, carbon dioxide
(60 times more than in
atmosphere), and oxygen
are the most abundant
gasses found in ocean
water cold water has more
dissolved gases in it
Oxygen and carbon
dioxide are essential for
plant growth
There is more gas found at
the surface of the water
where plant growth occurs
Gases and Ocean Facts
Colder temperatures hold more gas.
The ocean contains 60 times more
carbon that the atmosphere does.
The oceans are the most important
factor in regulating climate.
Salts in Ocean Water
Salinity is the amount of
dissolved salts in ocean
water
Sodium Chloride is the
most common salt
Average salinity of the
ocean is 35 o/oo
Salt comes from volcanic
activity, erosion of the land,
and wave erosion of
beaches
Sea salts
Parts per
Thousand
chloride
19.3 o/oo
sodium
10.7 o/oo
sulfate
2.7 o/oo
magnesium
1.3 o/oo
calcium
0.4 o/oo
potassium
0.4 o/oo
bicarbonate
0.15 o/oo
bromide
0.07 o/oo
other
0.06 o/oo
Total
Salinity
35.08 o/oo
Salinity
Salinity can be greater or
less than the average of
35 o/oo
Lower salinity where
freshwater rivers enter the
ocean
Salinity is higher where
there is greater
evaporation and in polar
regions where only fresh
water freezes
Animals using certain
salts to build their shells
can lower salinity
Deep Cold Water
Cold water holds more gas
than warm water
When the colder denser
water sinks to the bottom it
carries oxygen rich water
that aids in the survival of
deep water species
Temperature of Ocean Water
The sun is the major source
of heat for the ocean
Surface zone -100-300
meters deep, temperature
fairly constant, waves and
surface winds mix the water
and transfer the heat
downward
Temperatures (cont)
Thermocline- found
directly under the
surface zone,
temperature drops
rapidly, less dense
warm water floats on
top of the more dense
cold water
Temperature (cont)
Deep zone- has extremely
cold water, extends from the
thermocline to depths of
4000 meters or more,
temperature decreases only
slightly
Temperature below 1500
meters is only 4°
Temperature
The three ocean zones are not
found in the Arctic or Antarctic
The surface temperatures are
always very cold
Density and Color
The density of the
water gets greater
the deeper and
colder the water is.
Blue wavelengths of
light are reflected
Phytoplankton can
affect the color of the
ocean can show the
health of the ocean
Upwelling
The movement of deep, cold, and nutrient
rich water to the surface to support life.
Ocean Life Zones
Plant and animal life in the ocean
is affect by three factors: amount of
sunlight, temperature, and pressure
Plants and animals can be
classified into three major groups
according to their habitats of the
water in which they live
Plankton
Largest group of animals and
plants that float at or near the
surface
These get the most sunlight
Found at depths of 1 to 200 meters
deep
Very small organisms (plankton
that whales eat)
Nekton
Contains all forms of organisms
that swim around
They can actively search for food,
prey or predators
These are found in all areas of the
ocean
Benthos
Organisms that live on
the ocean floor
Benthic plants live in
shallow water so they
can get the necessary
sunlight
Oysters, crabs,
starfish are all benthic
Some even live in the
deepest parts of the
ocean
Ocean Environments (Zones)
The
classification of
the ocean into life
zones is based
on the conditions
of the oceanconditions that
vary widely
Intertidal Zone (Benthic Zone)
The region that lies between low
and high tide
Organisms must be able to live
without water some of the time
They must find someway to attach
so they are not washed out when
tide goes out
Includes anemones, crabs,
mussels, and plants
Neritic Zone (Pelagic Zone)
Extends from the low tide line to the edge of the
continental shelf
Depth of about 200 meters
Receives plenty of sunshine
Pressure is low and temperature is constant
Plankton, nekton, and benthos plants and
animals are found here
Riches part of the sea: contains fish, clams,
snails, some smaller whales, and lobsters
Much of the seafood we eat is found here!
Open-Ocean Zones
Bathyal zone begins at the continental
slope and ends about 2000 meters
Sunlight cannot penetrate to the bottom
Squid, octopus, and large whales are
found here
Abyssal zone extends to over 6000 meters
No sunlight can penetrate, high pressure
and low temperatures
Most animals are small and strange!