Introduction To the Oceans
About
71% of the surface of the planet is covered in salt water.
Beneath
the depth averages 3,8 km giving it a volume of 1370 x
106 km3.
Since
life exists throughout this immense volume, the oceans constitute the single largest
repository of organisms on the planet.
Introduction To the Oceans
These
organisms include representatives of all phyla and
are tremendously varied but all are subject to the properties of the sea water
that surrounds them.
Many
features common to these plants and animals are the results of adaptations to
the watery medium and its movements.
Introduction To the Oceans
Its
necessary therefore, to examine the physical and chemical conditions of
seawater and aspects of its motion (oceanography) and look at the environment
where the organisms live.
Introduction To the Oceans
Hydrologic
(Water) Cycle
Introduction To the Oceans
Where is all
the Water?
Introduction To the Oceans
Ocean Basins
Introduction To the Oceans
Ocean Basins
Introduction To the Oceans
The
mean depth is 4km (2.5 miles)and its interconnected
from the Arctic to Antarctic.
Seawater
flows freely among the basins transporting dissolved materials, heat and marine
organisms.
Seawater
mixes from basin to basin/per 1000 years but regional characteristics of the
seawater do exist.
Introduction To the Oceans
The
major basins are the Pacific, Atlantic, Indian, Arctic, Southern ocean and the
boundaries are artificially defined.
Introduction To the Oceans
Seawater
mix
Movement
of water moderates world climate by distributing heat from equatorial water to
the poles.
Warm
currents flow toward the poles from the equator (Gulf Stream) heating northern
latitudes.
Cold
water from the Arctic and Antarctic basins flow beneath the oceans surface
toward the tropics...cooler water near the equator.
Introduction To the Oceans
SEA
LEVEL
The
sea level has undergone dramatic changes. 15000 years ago 120m below present
level.
As
it fell portions of the continental shelf were exposed changing position of
coastline.
Ice
age/Wisconsin glacial period, the ocean water froze into glaciers.
Introduction To the Oceans
SEA
LEVEL
Introduction To the Oceans
It
is still rising.
The
rise slowed 3000 years ago and has only risen 10m since.
CO2
is warming the
Earth and the ice could melt and flood low lying areas in the next 1000 years..
Green House effect.
Introduction To the Oceans
The
Ocean Floor
Prior
to the 1920's, they used weighted rope to probe depths.
1920's
the echo sounder (SONAR-(sound navigation and ranging) which analyzed sound
waves which bounced off the oceans bottom and returned to the ship.
The
Meteror (1925-7) did the 1st ocean survey with sonar.
Introduction To the Oceans
Common
topographical features of the oceans include: Continental margin and deep sea
as the major divisions. Continental Margin
Continental shelf-underwater extension of
the continental land mass.
8%
of the total surface area of the world ocean, yet its one of the most
productive parts of the ocean.
It
gradually drops down to the 100-200m depth.
Introduction To the Oceans
Formation
of Continental Shelf
Introduction To the Oceans
Continental
slope begins where continental shelf plunges down.
As
the steepness decreases, this zone is called the continental rise.
Introduction To the Oceans
Locations
of Continental Shelfs
Introduction To the Oceans
Soft
sediment of the shelf exposed to erosion from rivers and then the glaciers
started to melt, excess water cut canyons into the
shelf.
Ocean
refilled, flooding shelf and forming underwater canyons.
The
rise slowed 3000 years ago and has only risen 10m since.
Introduction To the Oceans
Underwater
canyons occur in the margins which resulted from when the ocean level was lower with rivers
flowing over them eroding the soft sediments making deep gouges.
Underwater
landslides along the sides of the canyons make the canyon bigger
Introduction To the Oceans
Introduction To the Oceans
Types
of Reefs
Fringing-along
the land
Barrier-a
lagoon between the land and reef
Atoll-a
reef around a lagoon (formally an island since eroded.
Introduction To the Oceans
Types
of Reefs
Introduction To the Oceans
Trench Formation
Converge:
one plate dives under another, crumples and forms trenches...
Introduction To the Oceans
Turbidity
Currents
Avalanche-like
sediment movements caused when turbulence mixes sediments into water above a
sloping bottom.
Since
this sediment-filled water is now denser than the surrounding water, thick,
muddy water can run down the slope at speeds up to 17mph.
These
currents may have been responsible for enlarging submarine canyons
Introduction To the Oceans
Turbidity
Currents
PLATE TECTONICS
There are 8 major plates, up to 100 miles
thick and move slowly.
They know the direction and speed so can
figure out what the continent was like before it moved.
The Atlantic has been growing for 150 mil
years.
The theory of continental drift or plate tectonics
was only established in the 1960's. 200
million years ago, Pangaea fractured and started moving apart
180 mil. yrs ago.
Plates
PLATE TECTONICS
ALFRED
WEGENER
(1880-1930) German climatologist and geophysicist who, in 1915, published as
expanded version of his 1912 book The Origin of Continents and Oceans.
This work was one of the first to suggest continental drift and plate
tectonics.
PLATE TECTONICS
He
suggested that a supercontinent he called Pangaea
had existed in the past, broke up starting 200 million years ago, and that the
pieces ``drifted'' to their present positions. He cited the fit of South
America and Africa, ancient climate similarities, fossil evidence (such as the
fern Glossopteris and mesosaurus), and
similarity of rock structures.
PLATE TECTONICS
The force that moves the plates over the
semi-solid layer of the upper mantle /asthenosphere
is the convection currents
(large temp. difference between the mantle and crust) and moves
plates either
1. apart,
2. together or
3. laterally.
Plate Boundaries
Surtsey,
Iceland;63.30 N 20.62 W;170 m elevation
This photo, taken on November 30, 1963, shows the sixteen-day-old cone which
became the Island of Surtsey, off the southern coast
of Iceland. Born from the sea, it has provided scientists a laboratory to
observe how plants and animals establish themselves in new territory. The
eruption began 130 m below sea level, where it proceeded quietly until the
height of the volcano approached the sea surface. Then the explosive activity
could no longer be quenched by the sea. A black column of volcanic ash
announced the island's birth on November 14, 1963. Jets of dense black ash shot
skyward and the towering eruption cloud rose to a height of 9 km. By April of
1965, ash had blocked sea water from the crater area. Lava flows became
prominent, forming a hard cap of solid rocks over the lower slopes of Surtsey. This prevented the waves from washing away the
island. The three and one-half year eruption was over in June 1967. Photo
credit: Howell Williams
PLATE TECTONICS
1. apart new material rise as magna /molten
rock filling spaces (rifts form mid ocean ridge.
evidence
1965 research vessel Eltanin did magnetic studies
1969 Glomar
Challenger did cores from Pacific-Antarctic ridge
1977 Project Famous used submersibles
PLATE TECTONICS
2.
Converge one
plate dives under another, crumples and forms trenches...usually but not always
(mountains)
the area
is called a subduction zone
Island arcs formed/volcanos/
from turbulence from the melting of the descending plate.
PLATE TECTONICS
3.
Lateral-sideswipe and cause earthquakes volcanoes and deformations
PLATE TECTONICS
Mineral deposits in trenches and ridge
areas related to tectonic movements.
Geo-sil theory concentration
of copper and other metals form as plates melt and separates from crust
material, rise in subduction zone near trenches and
continues rising until it cools and gets exposed by weathering rocks.
PLATE TECTONICS
Hydrothermal vents...water percolates
into fissures around the rift valley, sinks and heats to 320'C in fissures
(pressure).
The heated water dissolves metals and it
rises to the seafloor surface,openings flow through
the hydrothermal vents, mix with cold water, minerals settle to bottom forming
deposits.
Robert Ballard witnessed milky bluish
clouds spewing in a Pacific rift zone.
Global
Hotspots
Caribbean
Tectonics
Puerto Rican
Tectonics and Seismic Hazard
Puerto Rican
Tectonics and Seismic Hazard
\
Seawater
Chemistry
1.Q. Does the saltiness of seawater
vary?
Q. What makes
seawater salty?
2.Q.
Where does the salt come from?
Q. Is the
ocean getting saltier?
3.Q.
Do the components of seawater all behave similarly?
4.Q.
How variable is the composition of salts in seawater?
5.Q.
Which gases are dissolved in seawater?
6.Q.
What role do the gases play in sustaining life in the ocean?
7.Q.
Can the salt be removed from seawater?
Water Chemistry Information
n
Pressure
n
Air
is .1% as dense as water and the ocean pressure is directly proportional to its
depth and acts in all directions within the water
n
6/3/2002
Pressure
n
The
atmospheric pressure is 1kg/cm2 (14.7lbs/sq in)= 1
ATM. An increase of 1 atm for each 33' or 10m and at
30m (100') the pressure is 4atm (1atm/10m + 1atm for air). Mariana trench
11,034m (36192')= 1000atm.
Pressure
n
This
is known as hydrostatic pressure and because of it, many organisms restricted to
particular level or depth and those that can go to all areas have evolved
adaptations to compensate for the change.
Density
n
Salt
water is 800x greater in density than air (supports
big organisms).
n
The density is affected by temperature.
n
As water cools,
Density
n
1.
water molecules move closer, increasing
density..
n
2.
4'C max density (1g/cm3)
n
3. cooler
decreases density..ice=
.92g/cm3 and is less dense so it floats.
Temperature:
n
Water
has a high heat capacity...ability to resist rapid temperature changes and is
transferred by convection.
Temperature:
n
Temperature
is the most important physical factor in the marine environment limiting the
distribution of ocean life by effecting density, salinity, gas concentration in
oceans.
Temperature:
n
There
is minimum vertical mixing because warm water (on top) can't replace cold
water.
n
The
thermocline is a narrow zone between warm surface
water and cold bottom water. Temperature effects ectotherms and endotherms.
Temperature 2
n
It
also affects the density as does salinity so both
salinity and temperature must be considered to work out density, salinity and
oxygen level. Variation of -2 (28) to
+30 (86).
Temperature 2
n
Satellites
are now used to monitor water temperatures
Gases
n
Gases
enter the ocean by diffusion from the atmosphere until it reaches saturation
level...different for each gas.
Oxygen
n
O2
makes up 21% of the atmosphere but in the coldest oceans its
less than 1% to as much as 9%.
Oxygen
n
O2
comes from photosynthesis in the ocean and this diffuses into the air because
water can only hold small amounts of O2.
n
The
ocean provides 50% of atmosphere O2.
Gases
n
The
most important are O, CO2 and N.
n
Dissolved
O2 = aerobic (use O2) and
n
none= anaerobic...
n
used for
respiration and corrosion.
Oxygen
n
Turbulence
increases the amount of O2 that can dissolve in water.
n
Dissolved
O2 declines rapidly as depth increases...why??
Zones
n
At
the depth where photosynthesis=rate of respiration its
the compensation depth.
At
the surface as O2 is used, its replaced quickly by
photosynthesis and as it deepens, respiration becomes greater than
photosynthesis.
Light
n
Used
for photosynthesis by plants with chlorophyll.
n
Much
is reflected back to atmosphere and as wave action increases, more is
reflected.
Light
n
Lots
are absorbed by water but 65% of all light is absorbed within the 1st meter and
only 1% gets to 100m.
Light Absorption
Zones
n
The
sunlit area is the photic zone where 70% of worlds
photosynthesis.
n
Lower
area (not sunlit) is the aphotic zone =90% of the
ocean
n
Photic
zone ranges from 1m in estuaries to 100m in open ocean
and depends on turbidity.
n
Turbidity
increases along the coast as suspended solids increase.
n
This
causes a shift of balance because where blue is the predominant absorbed light
in crystal clear water, suspended solids enable wavelengths of green to penetrate
deeper than blue in coastal waters.
n
The
highly productive water of the coast is greenish and estuaries are brownish.
n
The
compensation depth is shallower in coastal waters and below this the autotrophs can't get enough light for photosynthesis to meet
the energy requirements.
Salinity
n
Salinity
is expressed as concentration of ions in a liter of water or # of grams of
dissolved solids in 1000g of seawater.
Solvent
n
Water
is a solvent for most substances especially salts.
n
The characteristics of seawater are due to the
nature of pure water and the materials dissolved in it.
Solvent
n
The
solids in seawater come from two sources, the chemical weathering of rocks
washed to the sea by the rivers and the earth's interior through hydrothermal
vents.
Seawater Composition
n
Water...the
wonderful stuff held together by hydrogen bonds which causes ice to melt at 0
instead of -90.
n
It
causes the absorption of lots of heat to melt ice and same to evaporate
water...cooling.
Seawater Composition
n
It
allows water to hold heat...heat capacity and the amount of heat needed to
change water temperatures help for cooling of the earth
Components of Sea Water
n
Major
components of seawater vary slightly.
n
Two
processes add salts to the ocean--river discharge and water circulations
through hydrothermal vents (hotsprings).
Components of Sea Water
n
All
ocean water cycles through these vents every 8-12 million years.
n
These
work together making seawater, with the springs adding and removing chemicals.
Salinity
n
Salinity
is expressed as concentration of ions in a liter of water or # of grams of
dissolved solids in 1000g of seawater.
Salinity
n
Seawater
1000g samples have 34.7g of dissolved matter so salinity is expressed as 34.7 ppt (0/000) or 3.47
% .
n
The remaining 96.5% is pure water.
Salinity
n
Today
they can measure electrical conductivity in conjunction with temperature of
water sample.. conductivity
is proportional to salinity
Salinity
n
Also even though organisms may be exposed to changes
in salinity...rivers rain etc, they don't have to deal with changes in ratios
of the various ions dissolved in the seawater..
Salinity
n
Although
constant, the concentration can change with addition or removal of water.
n
Different
in local areas depending on rate of evaporation/precipitation and volume of
fresh water dumped.
Salinity
n
[red sea=40, Mediterranean=38
lack of rain fall and high evaporation. Black Sea=18 Baltic
Sea=8..low evaporation and high runoff.]
More Terms
n
Euryhaline=organism
can tolerate large salinities and fluctuation.
n
Stenohaline
can't tolerate large salinity changes.
n
Vertical
change surface layer mixed..uniform
beneath the halocine layer
large salinity changes above..The salinity changes with depth.
#19
Temperature!
Because of the great strength and large
number of hydrogen bonds between water molecules, more heat energy must be
added to speed up molecular movement and raise the waters temperature than would be necessary in
a substance held together
21-22
Bicarbonates absorb acid build up in the
sea
Nitrogen is fixed by blue-green algae as
nitrates which then can be used by plants to make proteins!
Density
n
Some
organisms have glycoprotein in their blood lowering freezing point of their
internal fluid.
Seawater Composition
n
Water...the
wonderful stuff held together by hydrogen bonds which causes ice to melt at 0
instead of -90.
n
It
causes the absorption of lots of heat to melt ice and same to evaporate
water...cooling.
Review Even Answers
Mar
sci ocean floor/tect/chem.
Notes EVEN Ans.
2.
Remotely-Operated Vehicles (ROVs) used for deep-sea
work have the advantage of being _safer than are people-carrying vehicles.
4. A flat-topped seamount is called a: guyot
6If the ocean evaporated, Earth's most obvious feature would be:mid-ocean ridge
.8 The deepest places on Earth are: trench
10Transform faults are fractures along which lithospheric plates move: transverselyside to side
12Ice is_less--dense than water
14In addition to
mixing in from the air, oxygen enters seawater:
Photosynthesis
16The average
salinity of the world's oceans is about (%o = parts per thousand) 35ppt
18.
In iron deficient regions, adding iron to the oceans
might reduce global warming by: increasing photosynthesis and using up co2
20.
What is the use of RADAR. LORAN, and GPS?navigation
22.
What types of reefs form around islands?fringing,barrier, atolls
24.
How was the sea level different 15,000 years ago? Lower Why?Last ice age
26.
What evidence led to the acceptance of the theory of plate
tectonics/sea-floor spreading?magnetic/cores/sight
28.
What is a hydrothermal vent? Hot water returning to ocean floor Of what
importance are they?salts
30.
What is compensation depth?photo=resp
32.How does
hydrogen bonding increase waters ability to moderate ocean temperature?energy
must break bonds before temperature changes