Exploring Creation with Marine Biology
Module #1: The Oceans of Our Planet
I. The Geography of the Oceans
A. Coverage
1. 72% of the earth is covered by seawater.
2. 80% of the Southern Hemisphere is covered by H2O
3. There are 4 large ocean basins on earth.
a. Pacific-the largest ocean
b. Atlantic-the 2nd largest ocean
c. Indian-smaller than the Atlantic
d. Arctic-smallest and shallowest
4. Oceans are connected to many shallow seas.
a. Caribbean Sea
b. Arabian Sea
c. Mediterranean Sea
d. Gulf of Mexico
5. The interconnection of the seas and oceans allows for the movement of organisms from
one to the other
B. The Earth’s Structure
1. layers of the earth
a. crust- the thinnest layer-floats on the mantle
b. mantle-rock that is near its melting point-called plastic rock-sometimes solid,
sometimes liquid
c. outer core- slightly less pressure than inner core- motion of the outer core
produces the earth’s magnetic field.
d. inner core--made of solid iron under intense pressure.
2. Difference in types of crust--caused by chemical and physical differences, not just
whether or not it is covered by water
a. Oceanic Crust--more dense, floats lower on mantle and composed mostly of
basalt (solidified lava), dark in color and believed to be about 5km thick
b. Continental Crust--less dense, lighter in color, chemically different from basalt,
composed of granite, 20-50 km thick
C. Continental Drift and Plate Tectonics
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1. Continental drift-hypothesis by Alfred Wagner explaining how the continents appear to
once have fit together and how coal deposits on opposite shores of the Atlantic are similar
a. Pangea- super continent
b. Plate tectonics-the continents drifted apart and they are still drifting-the
movements of large plates on the earth’s mantle
c. Movement of plates caused by radioactive decay of elements producing heat,
causing plate movement
d. Some known plates: N. American, S. American, African, Arabian, IndoAustralian, Eurasian, Pacific plates and more
e. Where the plates meet there is either a ridge or a trench
1. mid-ocean ridge-continuous chain of volcanic underwater mountains-some rise high enough to form islands such as the Azores in the Atlantic
2. trench--deep depressions in the ocean floor
3. large amount of geologic activity around ridges and trenches
(earthquakes and volcanoes around trenches)
4. sediment-loose mud or sand that settles to the bottom-it is thicker away
from the ridge
5. magnetic anomalies--in molten rock there are tiny magnetic particles
that align with the earth’s magnetic field as the rock cools--scientists have
discovered a pattern of bands running parallel to the mid-ocean ridge
which have this anomaly (magnetic orientations of both north and south)
indicating to scientists that the layers of these rock were formed at different
times and that there was a time in the history of the earth when the
magnetic field was the opposite of today
a. layers formed at different times
b. sections of the earth’s crust near the mid-ocean ridge are moving
away from each other causing a crack or a rift between the plates
c. as the plates move a part, there is less pressure on the mantle
below, allowing the mantle material to melt enough to rise up
through the rift
d. upon reaching the surface, it cools and becomes new oceanic crust
e. as the mantle material rises, it also lifts up the crust around the
rift, forming the mid-ocean ridge
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f. This process is called sea floor spreading-- creation of new sea
floor
6. Catastrophic plate tectonics—very rapid plate movements during the worldwide
Flood that occurred in Noah’s day
D. Features of the Ocean Bottom—4 regions
1. Continental Shelf—shallow section of the edge of the continent extending from the
shore to the point where the slope gets steeper and makes up about 8% of the ocean’s
surface area but contains the richest part of the ocean where most of its life is found. This
region ends at the shelf break at a depth of 120-200meters
2. Continental Slope—steep slope extending from continental shelf to ocean
3. Continental Rise—gently sloping area (at the base of the rise) made of a buildup of
sediment
4. Abyssal plain—flat area 3,000-5,000 meters. The Mariana Trench reaches to a depth of
6.8 miles (11,020 meters)
II. Properties of Water
A. Excellent solvent—anything that has a charge will dissolve in water, i.e. polar molecules such
as salts
B. High boiling and freezing points (212 F/ 100C and 32 F/0 C)
C. Denser as liquid than as a solid which allows for the
floating of ice on top of lakes and
oceans--resulting in this unusual insulating characteristic
D. Polar—oxygen is slightly negative and hydrogen is slightly positive. This causes a separation of
charges
E. Hydrogen Bonds—water can form H Bonds because of the polarity of the water molecule— weak
attractive forces between H+ of one molecule and the O- of another water molecule
F. Cohesive—water molecules stick together and create surface tension -(greater attraction for
other
water molecules than for air molecules)
G. Specific Heat—(high for water)—the amount of heat energy needed to change the
temperature
of one gram of water (1 cubic cent.), 1 degree.
III. Salinity, Temperature and Density
A. Salinity—the total amount of salt dissolved in a solvent. Salt accounts for 85% of all dissolved
solids in the ocean
1. measured in ppt (parts per thousand)
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2. smallest changes in salinity can kill an organism
3. salts dissolved in water form ions—SEE Table 1.2, pg 16
4. Cycling of sea salts
a. rocks release ions into water
b. volcanic eruptions produce gases-dissolve in rain water and enter the ocean
c. river water carries large amounts of ions
d. 250 million dump trucks of salt are added to the ocean per year
e. salt is lost from water as sea spray when waves hit the beach
f. salt is cycled through organisms
g. salt sticks to particles suspended in the ocean and settles to the bottom
h. salt removed when organisms are caught and removed
B. Gases in Sea Water
1. The amount of gas that water can hold depends on the temperature, salinity and
pressure of water. Cold water holds more gas than warm water. More gas will
dissolve if salinity is low and gas pressure is high.
2. Gas In Atmosphere SEE TABLE IN BOOK
3. Ocean Heating and Cooling
1. Sun’s radiant energy warms the earth’s surface
2. Tropics receive the most radiant energy
3. When sun’s rays are at a right angle there is a greater amount of solar energy
received on Earth
4. Greater the angle, i.e. > 90 degrees there is less solar energy
D. Ocean layers and vertical mixing
1. Role of salinity and temperature in forming ocean layers.
a. Density—mass of a substance in a given volume seawater has a higher density than
pure water— controlled by variations in surface temperatures and salinity
b. Density increases w/ increase in salinity and decrease in temperature
c. Water reaches maximum density at 4 degrees Celcius
d. Density decreases w/ decrease in salinity and increase in temperature
e. Salinity increases when evaporation occurs or when some of the sea water comes out
to form ice
f. Salinity decreases with precipitation, river water entering the ocean, melting ice.
g. Pressure affects density of sea water but at the surface, minor effects
h. All of this creates regions of oceans with different densities
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i. Denser water sinks, less dense water rises and produces layering the oceans
2. Thermocline—A layer in a large body of water that
temperature, so that
sharply separates regions differing in
the temperature gradient across the layer is abrupt –this graph shows
the
presence of a thermocline between 100 and 200 meters. These occur 330feet-3300
3. Halocline—layer of ocean where salinity increases in a strong vertical gradient at
depths of 330-3300 feet
4. Pycnocline—layer where density increases rapidly
a. If density increases w/depth—it is a stable water column
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b. If density is higher at the surface—water column is unstable and the denser
water will sink and water column will become stable
5. Isopycnal—the surface of constant potential density of water
a. when the water column is stable it can be vertically mixed easily by wave, wind,
etc.
b. vertical mixing is important—as rich organic nutrients on bottom can be moved
up and oxygen rich water on surface can move down
c. Thermohaline circulation—this is when density is controlled by temperature
and salinity
d. Summer—stable water column in temperate latitudes
e. Fall—water cools, increase density, water column becomes unstable at the
surface and water sinks. Continues with winter storms
f. Downdwelling zones—area where surface water is sinking
g. Updwelling zones—bottom water rises to the surface
h. Organisms can live in areas where downdwellings occur-as oxygen is moved
down
i. Wind can cause downdwelling when wind drives masses of surface water
together, water is forced down
6. Tides—shifting pattern of water levels
a. Full tidal cycle is 24 hours and 50 min.—most areas on earth will experience two high
and two low tides each day
b. Tides are affected by the gravitational pull of the sun and moon
c. The moon exerts twice the pull as sun due to its proximity to earth
-This refers to tidal effects
d. Spring tides—highest and lowest tides—due to alignment of the sun and moon and
earth in a straight line and occurs during full and new moons and can occur every two
weeks not just in spring
e. Neap Tides—lower high tides and higher low tides—occurs when sun and moon are at
right angles to each other—partially cancelling out the gravitational pull of each other
f. Tides are diurnal—one low and one high tide two times each day
g. Flood tide—the period between low and high tide when the water is rising toward the
shore (rising tide)
h. Ebb tide—the period between high and low tide when the water is flowing away from
shore (falling tide)
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i. Slack water—when tidal currents slow down and reverse
j. Tides—occur when the gravitational force of the moon pulls ocean water toward it on
one side of the earth while on the opposite side of the earth the centrifugal force of the
earth causes the water to bulge. This causes the high tides, while the low tides develop due
to the equalizing of the gravitational and centrifugal forces
1. High tide-when the gravitational or centrifugal forces are unequal, one being
higher than the other
2. Low tide-when these forces are equal
E. Winds and Currents
1. Surface currents are driven by winds
2. Air heats and it rises, cools and it falls
3. Two sets of winds—surface winds and upper level winds (jet stream)
4. Wind Patterns
a. At equator, hot air and warm waters—less dense air rises
b. At the poles, air cools and because it is denser, sinks, increasing surface air
pressure- cool air is low in moisture
c. this denser air is drawn toward the equator to replace the air that has moved
away and risen into the atmosphere
5. Trade winds blow toward the equator, westerly and at a 45 degree angle, they are
considered the most consistent winds on earth
6. Westerlies are winds that come from the west, and move in the opposite direction of the
trade winds and are more variable due to land formations
7. Polar easterlies are the northernmost and southernmost winds and are the most
variable of all winds
8. Major winds push on ocean surface and create currents
9. The winds push the surface waters all around and create large surface currents
resulting in circular flows called gyre
F. Waves—result of forces acting on the water
1. waves move energy along the water but there is very little forward movement of actual
water molecules-- energy is transferred through waves
2. See Fig. 1.17, page 2
3. Capillary waves are small waves created when water is displaced and water is restored
through surface tension
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4. Gravity waves are larger waves in which a large amount of water is displaced and
restoration is through gravity
a. Wind blows across surface of water-creates friction that lifts water away from
surface
b. Waves in ocean do not represent a flow of water but a flow of energy or motion
c. Swells—uniform waves
d. Surf zones—area along coast where waves slow down
e. Tsunamis-a geologic wave caused by a large disturbance such as an earthquake,
a shift in ocean floor, hurricane, explosion- causing huge waves ( in Japanese
means Harbour wave)
G. Vertical Motion
1. The ocean has two main layers separated by a thermocline layer
2. surface layer is 100-200 meters(330-660 ft) thick
3. Thermocline is a transitional layer between the warmer top layer and the colder
bottom layer and is found away from continental shelf
4. Deep layer is found below 1500 meters and is uniformly cold and thicker than the other
two layers
5. The water column is the group of water layers
6. Deep water is cold and dense, surface water is warm and less dense.
7. A water column that varies a lot in densities is considered a highly stable water column
and does not mix much w/o a storm.
8. A water column that has consistent density throughout mixes easily.
a. surface water can become denser through evaporation or can cool from air
temperature/seasonal changes
b. surface water sinks causing the less dense water to be displaced in a
process called overturn mixing
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