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OUR OCEAN PLANET
OUR OCEAN PLANET
SECTION 1 – OUR OCEAN PLANET
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1. OUR OCEAN PLANET
1. OUR OCEAN PLANET
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1.1 THE OCEAN
1.1 THE OCEAN
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1.1 THE OCEAN
1.1 THE OCEAN
Although we refer to our planet as Earth, the most dominant physical
feature of our planet is the ocean which covers more than 70% of
the planet’s surface. The total area covered by ocean is about 362
million sq km (140 million sq miles) with an average depth of 3,720
m (12,200 ft). The ocean so dominates the planet and is so
important to us that Earth should perhaps be thought of as the
“ocean planet”.
Our planet’s ocean is connected by currents and can thus be
considered to be one continuous ocean. However, it is customary to
divide it into 5 individual oceans, namely, the Pacific, Atlantic, Indian,
Antarctic (or Southern) and Arctic Oceans. We can also further
divide the Pacific and Atlantic Oceans into the North and South
Pacific, and the North and South Atlantic Oceans.
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1.1 THE OCEAN
Ocean
Area (million sq km)
Area (million sq miles)
Pacific
153
59
Atlantic
82
32
Indian
67
26
Antarctic
21
8
9
3
Arctic
Ocean Literacy Principle 1(a)
The ocean is the dominant
physical feature on Earth –
covering approximately 70% of
the planet’s surface. There is
one ocean with many ocean
basins, such as the North
Pacific, South Pacific, North
Atlantic, South Atlantic, Indian
and Arctic.
1.1 THE OCEAN
An “ocean” is a very large body of saltwater while a “sea” is a much
smaller body of saltwater that is considered part of its closest ocean.
Thus, the Coral Sea is considered part of the Pacific Ocean while
the Caribbean Sea is considered part of the Atlantic Ocean. The
term "sea" is often given to a saltwater area on the margins of an
ocean (e.g. the Mediterranean Sea is beside the Atlantic). A sea is
also often enclosed or partially enclosed by land while an ocean is
on the margin of land. The difference is not entirely precise and
there are exceptions to the general definition.
The ocean generally looks blue because seawater does not absorb
blue light from sunlight. When sunlight hits the water, the blue light
is scattered in all directions making the ocean look blue. In seas or
oceans that appear to be green, the colour is generally due to plants
in the water. The northern Atlantic and Pacific Oceans, for example,
are green near the coast because of a rich abundance of plants in
the water. In contrast, the clear blue waters of the Caribbean Sea
indicate the absence or reduced number of plants.
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The ocean covers a number of ocean basins including the North
Pacific, South Pacific, North Atlantic, South Atlantic, Indian and
Arctic basins. An ocean basin at the bottom of the sea is composed
of numerous underwater islands, trenches, mid-ocean ridges, rift
valleys and sea mounts.
The sea bed may move as a result of lithospheric plate activity.
Volcanic activity also occurs underwater which can cause violent
land-forming activity. Earth’s highest peaks, deepest valleys, and
flattest, largest plains are all in the ocean. We will explore some of
the ocean’s features in the rest of this section.
The ocean is not a just a large static volume of water but a highly
dynamic system. Each ocean has large surface circulating currents
that transport warm surface water from the equator towards the
poles, and cool polar water towards the equator. These currents are
called “gyres” and they travel clockwise around ocean basins in the
northern hemisphere, and anti-clockwise in the southern
hemisphere.
Ocean Literacy Principle 1(b)
An ocean basin’s size, shape
and features (islands, trenches,
mid-ocean ridges, rift valleys)
vary due to the movement of
Earth’s lithospheric plates.
Earth’s highest peaks, deepest
valleys and flattest vast plains
are all in the ocean.
Ocean Literacy Principle 1(c)
Throughout the ocean there is
one interconnected circulation
system powered by wind, tides,
the force of the Earth’s rotation
(Coriolis effect), the Sun, and
water density differences. The
shape of ocean basins and
adjacent land masses influence
the path of circulation.
1.1 THE OCEAN
Interconnected circulation systems powered by the force of the
Earth’s rotation (Coriolis effect) and the Sun’s heat transports water
from the surface of the ocean to the bottom of the ocean and back
again. The driving force in this vertical mixing process is differences
in water density – cooler deep water is denser than warmer surface
water resulting in vertical mixing.
The shape of ocean basins and adjacent land masses also influence
the path of both surface circulation and deep mixing.
At sea level, a variety of forces, such as the Sun and Moon, act on
the ocean to stir and move the water. This movement can be gentle
as the lapping of water at the ocean’s edge, or extremely violent with
huge waves that can destroy whole swathes of coastline.
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1.1 THE OCEAN
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1.1.1 Plate Tectonics
The Earth can be divided into three basic layers, namely, the core,
mantle and crust. Plate tectonics explains the movement of the
continental crust in the upper layer of the Earth. Heat and magma
from the interior of the Earth rises and cools as it reaches the upper
mantle. This causes movements of the Earth’s crust and shifting of
large sections of the crust known as “tectonic plates”. Plate
tectonics cause ocean basins, earthquakes, mountains, volcanoes
and faults to form. This dynamic process, driven by the heat deep
inside the Earth, is what sets the Earth apart from any other planet.
It is now recognized that the surface of the Earth has at least 7
major plates and a large number of smaller ones, all floating on the
partly molten layer of the mantle beneath. Some of these plates
carry continents while others are purely oceanic.
The areas where these plates meet are called “plate boundaries”.
Different types of powerful natural phenomena occur at these
boundaries depending on the type of boundary.
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1. DIVERGENT BOUNDARY
At a divergent boundary, plates are moving apart as hot magma
rises and moves upwards to the surface of the earth. When the
magma reaches the surface, it cools and solidifies to form a new
crust. Imagine two giant conveyor belts, facing each other but
slowly moving in opposite directions as they transport newly formed
oceanic crust away from the ridge crest. This process continues
over many millions of years and eventually results in the formation of
an ocean basin. Examples include the Mid-Atlantic Ridge which
spread apart to form the Atlantic Ocean and the Red Sea. Divergent
boundaries may give rise to volcanoes and earthquakes.
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1.1 THE OCEAN
2. CONVERGENT BOUNDARY
At a convergent boundary, the plates move toward each other. If an
oceanic plate and continental plate collide, the denser oceanic plate
is forced underneath the continental plate, forming a subduction
zone. As the oceanic plate is forced below the continental plate, it
melts and becomes magma. The magma collects to form a magma
chamber and may rise up through cracks in the continental crust. As
pressure builds, a volcanic eruption may occur.
When two
continental plates push towards one another, the continental crust is
squashed together and forced upwards to form mountain belts. This
is how the Himalayas were formed. Convergent boundaries may
give rise to mountains, volcanoes, faults, and earthquakes.
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3. TRANSFORM BOUNDARY
At a transform boundary plates slide horizontally past each other.
Transform boundaries do not create or destroy land and often give
rise to earthquakes and major faults but not volcanoes. A wellknown example is the San Andreas Fault, which runs through the
state of California in the USA.
Volcanic and earthquake activity is frequent at active plate
boundaries and can be extremely violent. For example, in the
Pacific Ocean, the "ring of fire" is a rough ring or circle stretching
from New Zealand, along the eastern edge of Asia, north across the
Aleutian Islands of Alaska, and south along the coast of North and
South America. It is where the Pacific Plate interacts with other
plates such as the Indo-Australian and North American plates. Over
75% of the world's active and dormant volcanoes are found along
the ring of fire.
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1.1 THE OCEAN
In the Caribbean, the island of Monserrat has an active volcano that
began erupting in 1995 and it is still continuing to so today. The
North American tectonic plate is subducting beneath the Caribbean
plate and forming the entire Lesser Antillean Island Arc system. The
island arc is a series of volcanic islands that are formed as a result
of this convergent tectonic activity.
In the figure below, some of the Earth's major plates are shown with
dotted lines indicating the plate boundaries. An arrow indicates the
direction in which the plate is moving. The “ring of fire” is also
outlined with a solid line.
Note that the figure is only an
approximation and is not intended to be definitive.
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REFERENCES & FURTHER READING
http://www.mvo.ms/
http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_plate_tectonics_world.html
http://www.bbc.co.uk/schools/gcsebitesize/geography/platetectonics/index.shtml
http://pubs.usgs.gov/gip/dynamic/understanding.html
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1.1.2 Sea Level
Sea level is the average height of the ocean relative to the land
taking into account the differences caused by tides. The sea level is
not constant but changes over time.
1. SHORT TERM
Some short-term causes of sea level changes include:
(a) Tides
The tides, which are caused by the gravitational pull of the Moon
and the Sun on the Earth, regularly change the sea level so that it
oscillates between high tide (the highest sea level) and low tide (the
lowest sea level).
(b) Storm Surges
Storm surge is caused primarily by high winds pushing water toward
the shore causing the sea surface to rise. The wind causes the
water to pile up higher than the ordinary sea level.
(c) Seawater Expanding/Contracting
Sea levels also change as sea water expands and contracts when
ocean water warms and cools.
(d) Flooding
River runoff levels or flooding due to seasonal differences in the
amount of rainfall can also cause changes to sea level.
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Ocean Literacy Principle 1(d)
Sea level is the average height of
the ocean relative to the land,
taking into account the differences
caused by tides. Sea level
changes as plate tectonics cause
the volume of ocean basins and
the height of the land to change. It
changes as ice caps on land melt
or grow. It also changes as sea
water expands and contracts
when ocean water warms and
cools.
1.1 THE OCEAN
(e) Earthquakes/Landslides
Undersea earthquakes can generate huge waves called tsunamis
that can temporarily change sea level. Abrupt landslides in the sea
can also change sea levels.
2. LONG TERM
Some long-term causes of sea level changes include:
(a) Plate Movement
Sea levels can change as shifting plates cause the volume of ocean
basins and the height of the land to change.
(b) Glaciers Melting
Sea levels can rise as mountain glaciers melt and the water enters
the ocean.
(c) Icecaps Melting
Sea levels can rise as icecaps break off and enter the ocean. Note
that the sea level rises when the ice first enters the ocean not when
the sea ice melts because the ice is already displacing an equivalent
volume of water.
REFERENCES & FURTHER READING
http://www.weatherincayman.com/tideprediction.html
http://www.tide-forecast.com/locations/GrandCayman-CaymanIslands/tides/latest
http://tidesandcurrents.noaa.gov/sltrends/sltrends.html
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1.1.3 Sea Floor
The sea floor is divided into a number of geographically distinct
areas depending on depth, plate tectonic zone, and distance from
the coast:
1. CONTINENTAL SHELF
The Continental Shelf lies between the coast and the 200 m (660 ft)
depth contour. The Continental Shelf surrounds the continents on
earth but occupies only 7.5% of the sea floor.
The shelf
corresponds to the submerged portion of the continental crust.
2. CONTINENTAL SLOPE
The downward slope of the Continental Shelf increases abruptly at
the seaward edge to form the Continental Slope, which occupies
8.5% of the sea floor. At a depth of about 3,000 m (9,842 ft), the
slope flattens out to a gradient of 1:100 and the beginning of the
Continental Rise.
3. CONTINENTAL RISE
The Continental Rise is typically a thick flattish wedge of sediment
that runs from about 3,000 m (9842 ft) to 4,000 m (13,123 ft). At
around 4,000m (13,123 ft) the Continental Rise levels out again to
an almost imperceptible gradient (1:1000 or less) to meet the
Abyssal Plain.
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4. ABYSSAL PLAIN
The Abyssal Plain extends from about 4,000 m (13,123 ft) to 6,000
m (19,686 ft). It is a huge flat floor of an ocean basin that is covered
with a layer of sediment. It covers over 50% of the ocean area and
is the single largest environment on Earth.
5. OCEAN TRENCH
The deepest places on the earth's surface are known as Ocean
Trenches. These trenches are like deep wounds in the ocean floor.
They form when two tectonic plates collide and one subducts
beneath the other, forming a depression. The deepest trench, the
Mariana Trench, extends to a depth of 11,033m (36,198 ft).
6. SUBMARINE RIDGES
In some oceans, narrow, elongated ridges, resembling mountain
ranges on the land, rise from the sea floor as a result of plate
tectonic collisions. These are called “Submarine Ridges”. Peaks of
these ridges may rise above sea level to form islands.
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Some of the features of the sea floor are as amazing as those we
see on land. For example:
DEEPEST TRENCH
The Mariana Trench, which is located in the western Pacific Ocean
southeast of the Mariana Islands, is the deepest point on Earth. At
11,033 m (36,198 ft), the Mariana Trench is farther below sea level
than Mount Everest is above it.
The Cayman Trench (also known as the Bartlett Deep or Bartlett
Trough) lies on the floor of the Caribbean Sea between Jamaica and
the Cayman Islands. This relatively narrow trough has a maximum
depth of 7,686 m (25,216 ft) and is the deepest point in the
Caribbean Sea.
TALLEST MOUNTAIN
Mountains are generally measured from sea level, in which case
Mount Everest (8,848 m; 29,028 ft) is the tallest. However, Mauna
Kea on Hawaii’s Big Island rises 10,203 m (33,476 ft) from the depth
of the Pacific Ocean floor. Measured from base to peak, Mauna Kea
is the tallest mountain on earth.
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GLOBAL MID-OCEAN RIDGE
The ocean ridges form a great mountain range wound around the
Earth like the seam on a baseball. The global mid ocean ridge is
about 64,000 km (40,000 miles) long and is the single largest
topographic feature on Earth. Several smaller mid-ocean ridges
make up the global mid-ocean ridge, one of the best-known being
the Mid-Atlantic Ridge which runs down the centre of the Atlantic
Ocean.
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REFERENCES & FURTHER READING
http://hypertextbook.com/facts/2001/BeataUnke.shtml
http://www.redcomet.org/Preview/Ces5xPrv.html
http://smithsonianeducation.org/educators/lesson_plans/science_technology.html
http://www.msstate.edu/dept/geosciences/CT/TIG/WEBSITES/RESEARCH/Christine_Oxenford/index.html
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1.1.4 Depth Zones
Scientists have divided the ocean into layers or "zones" based on the penetration of light and depths
which extend from the surface to the bottom of the ocean as follows:
1. EPIPELAGIC ZONE (PHOTIC ZONE)
The Epipelagic zone extends from the surface to a depth of 200 m (656 ft). The water in this zone is
fairly well mixed and, under ideal conditions, sunlight can penetrate the entire zone. Temperatures in the
Epipelagic zone vary with climate and season but the worldwide average temperature of the surface
zone is 22°C.
2. MESOPELAGIC ZONE (TWILIGHT ZONE)
The Mesopelagic Zone extends from a depth of 200 m (656 ft) to 1,000m (3281 ft). This zone is also
called the twilight zone and the mid-water zone. The sunlight in this zone is extremely faint. It is in this
zone that we begin to see the twinkling lights of bioluminescent creatures. A great variety of strange and
bizarre fish are also found here.
3. BATHYPELAGIC ZONE (DARK ZONE)
The Bathypelagic Zone extends from a depth of 1,000 m (3,281 ft) down to 4,000 m (13,123 ft). The only
visible light in this region is the light produced by bioluminescent life forms. The water pressure at this
depth is crushing but a surprisingly large number of creatures can be found. Sperm whales can dive
down to this level in search of food. Most of the animals that live at these great depths are black or red
in colour due to the lack of visible light.
1.1 THE OCEAN
4. ABYSSOPELAGIC ZONE (“ABYSS”)
The Abyssopelagic Zone extends from a depth of 4,000 m (13,123
ft) to 6,000 m (19,686 ft). Its name comes from a Greek word
meaning "bottomless". The water temperature of this zone is near
freezing and there is no light at all. Very few creatures can be
found at these depths because of enormous pressure. Most
organisms found at these depths are invertebrates and include
basket stars and tiny squids.
5. HADALPELAGIC ZONE (“TRENCHES”)
The Hadalpelagic Zone extends from a depth of 6,000 m (19,686 ft)
to 10,000 m (32,810 ft). This zone is mostly found in deep water
trenches and canyons.
In spite of the pressure and cold
temperature, life can still be found in this zone, particularly
invertebrates, such as sea stars and tubeworms, which thrive at
these depths.
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1.1.5 Oceans Past/Oceans Present
The ocean and continents didn’t always look the same as they do
today. In the past, one huge ocean called Panthalassa surrounded
the supercontinent of Pangaea because of plate (tectonic)
movements.
Pangaea was a C-shaped landmass that was spread across the
equator. The body of water that was enclosed within the resulting
crescent has been named the Tethys Sea.
The break-up of Pangaea took place about 180 million years ago,
first into the two supercontinents Gondwanaland (to the south) and
Laurasia (to the north), and thereafter into the continents we have
today.
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The sequence of maps to the right (adapted from the USGS) shows
how Pangaea continued fragmenting to form today’s ocean basins.
As the plates moved apart along divergent boundaries to create new
ocean basins, convergent boundaries resulted in subduction and
recycling of crustal material into the mantle.
The Earth's current continental landmasses formed and eventually
moved to their current positions.
REFERENCES & FURTHER READING
http://pubs.usgs.gov/gip/dynamic/dynamic.html
http://mineralsciences.si.edu/tdpmap/
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1.2 WATER
1.2 WATER
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1.2 WATER
1.2 WATER
1.2.1 What is Water?
Water is the most abundant resource on our planet. One molecule
of water is made up of one atom of oxygen and two atoms of
hydrogen, which is written as the chemical formula H2O. The two
hydrogen atoms lie at 105° to each other. This arrangement results
in the hydrogen end having a slightly positive charge and the oxygen
end a slightly negative charge. Since opposite charges attract,
individual water molecules come together through a weak attraction
called a “hydrogen bond”. Hydrogen bonds allow water to exist in
different states:
1. Ice (Solid)
When water is frozen, the molecules are held by hydrogen bonds in
a hexagonal structure.
2. Water (Liquid)
As the temperature rises, ice turns into water, the molecules move
freely, forming and breaking hydrogen bonds.
3. Water Vapour/Steam (Gas)
As the temperatures rises even further and the molecules vibrate
faster, the hydrogen bonds break, the molecules are set free, and
the liquid becomes water vapour. At high temperatures, water
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1.2 WATER
Water is able to change between these states by the addition or
removal of heat/energy. These transitions occur naturally between
the ocean, clouds and land, as we will see later.
1. Melting
Melting is the process by which ice (solid) warms up and becomes
water (liquid).
2. Sublimation
Sublimation is the process by which water changes from a solid (ice
or snow) to a gas bypassing the liquid phase. This happens in
places such as the Rocky Mountains as dry and warm Chinook
winds blow in from the Pacific in late winter and early spring. When a
Chinook arrives, local temperatures rise dramatically. When dry air
hits the snow, the snow becomes water vapour bypassing the liquid
phase. Sublimation is a common way for snow to disappear quickly
in arid climates.
3. Evaporation
Evaporation is the process by which water changes from a liquid to a
gas or vapour when heat is added to water.
4. Condensation
Condensation is the process by which warm water vapour in the air
cools and changes into liquid water as water droplets.
5. Freezing
As liquid water cools further, it becomes a solid (ice).
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1.2.2 What is Sea Water?
Water is a remarkable substance as it has many unusual properties
and can behave in unexpected ways. For example, it is a very good
solvent and is able to dissolve many elements.
Seawater is a complex solution and is composed of the following:
• 96% pure water
• 3% sodium chloride (common salt or halite)
• 1% other elements (e.g. magnesium, calcium, potassium)
Sodium and chlorine are the most abundant elements dissolved in
seawater. However, it is the combination of all of the different
elements and compounds dissolved in the ocean that make the
ocean “salty”.
Seawater has unique properties:
• it is saline
• its freezing point is slightly lower than freshwater
• its density is slightly higher that freshwater
• its electrical conductivity is much higher than fresh
• it is slightly basic (or alkaline)
Ocean Literacy Principle 1(e)
Most of Earth’s water (97%) is in
the ocean. Seawater has unique
properties: it is saline, its
freezing point is slightly lower
than fresh water, its density is
slightly higher, its electrical
conductivity is much higher, and
it is slightly basic. The salt in
seawater comes from eroding
land, volcanic emissions,
reactions at the seafloor, and
atmospheric deposition.
Interesting!
Ordinary seawater contains
about 35 parts per thousand of
salt (3.5%). In other words, 1 kg
of sea water contains 35 g of
salt. The density of sea water is
about 1.025 g/ml at the surface
of the ocean.
1.2 WATER
The salt in seawater comes from eroding land, volcanic emissions,
reactions at the sea floor, and atmospheric deposition.
The amount of dissolved salts in the oceans does not vary greatly
from place to place or from time to time throughout the ocean.
However, slight differences in salinity along with larger differences in
water temperature results in water masses with different densities.
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1.2.3 Where Does Earth’s Water Originate?
1. Magma
Primordial Earth was an incandescent globe made of magma. All
magmas contain water. Water set free by magma began to cool
down the Earth’s atmosphere until eventually it became cool enough
for the water to stay on the surface as a liquid.
2. Volcanoes
Volcanic activity kept (and still keeps) introducing water in the
atmosphere thus increasing the surface and ground water volume of
the Earth.
3. Comets
Scientists suspect that comets made of ice may have collided with
the Earth in the past, releasing their water into the oceans.
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1.2.4 Where Is All The Water?
All the water we will ever have is already here on Earth in one form
or another (except possibly for ice-laden comets striking the Earth).
Ocean Literacy Principle 1(h)
Although the ocean is large, it is
finite and resources are limited.
Of the total supply of about 1386 million cubic km of water in the
world, almost 97% of the total is saline. Of the 3% freshwater, ~69%
is locked up in ice and glaciers while ~30% of freshwater is in the
ground. Only 1% is readily available for drinking. Fresh surfacewater sources, such as rivers and lakes, only constitute about
93,100 cubic kilometers (22,300 cubic miles), which is only 1/700th
of 1% of the total water. Yet, rivers and lakes are the sources of
water most people use.
Interesting!
Largest freshwater area – Antarctica
(frozen) or Lake Baikal in Russia.
Antarctica is a continent covered
with ice but because the water is
frozen it is not easily potable.
Antarctica is also the driest
continent on Earth with very low
rainfall and with all moisture and
water locked up in the ice.
Saltiest sea is the Dead Sea
Certain bacteria and other
organisms can tolerate extremely
high salinity conditions (over 5 times
that of the ocean). These
organisms are called “halophiles”
(salt-lovers).
In considering how precious fresh water is, it is helpful to remind
oneself of the following quote:
"Water, water, everywhere,
And all the boards did shrink;
Water, water, everywhere,
Nor any drop to drink."
The Rime of the Ancient Mariner – Samuel Coleridge
1.2 WATER
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1.2 WATER
1.2.5 Water Cycle
Earth's water is constantly changing states from liquid to vapour to
ice to liquid again in a cycle that has operated for billions of years
and upon which all life on Earth depends.
The “Water Cycle” is driven by the sun which heats water in the
ocean. Some of it evaporates into the air as water vapour. Ice and
snow can also sublimate directly into water vapour. Rising air
currents take the vapour into the atmosphere along with water from
evapotranspiration (water transpired from plants and evaporated
from soil). Cooler temperatures here cause the vapour to condense
into clouds. As air currents move clouds around the globe, cloud
particles collide, grow, and fall from the sky as precipitation. Some
precipitation falls as snow and accumulates as ice caps and glaciers
which can store frozen water for thousands of years. Snow in
warmer climates thaws in spring and it flows overland as snowmelt.
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Ocean Literacy Principle 1(f)
The ocean is an integral part of the
water cycle and is connected to all
of the earth’s water reservoirs via
evaporation and precipitation
processes.
Ocean Literacy Principle 1(g)
The ocean is connected to major
lakes, watersheds and waterways
because all major watersheds on
Earth drain to the ocean. Rivers and
streams transport nutrients, salts,
sediments and pollutants from
watersheds to estuaries and to the
ocean.
1.2 WATER
Most precipitation falls as rain back into the oceans or onto land,
where the precipitation flows over the ground as surface runoff. A
portion of runoff enters rivers which transports the water towards the
oceans. Runoff and ground-water seepage accumulate and are
stored as freshwater in lakes. However, not all runoff flows into
rivers. Much of it soaks into the ground as infiltration. Some water
infiltrates deep into the ground and forms groundwater which can
flow or be stored in the rocks for long periods of time. Some
infiltration is close to the land surface and can seep back into lakes
and the ocean as groundwater discharge, while some groundwater
finds openings in the land surface and emerges as freshwater
springs. Over time, all water keeps moving, some of which reenters
the ocean to start the cycle again.
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1.2 WATER
REFERENCES & FURTHER READING
http://ga.water.usgs.gov/edu/watercyclehi.html
http://www.kidzone.ws/water/
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1.3 ACTIVITIES
1.3 ACTIVITIES
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1.3 ACTIVITIES
1.3 ACTIVITIES
1.3.1 Ocean
CORE ACTIVITY
(a) Find and label the world’s oceans:
 Pacific Ocean
 Atlantic Ocean
 Indian Ocean
 Arctic Ocean
 Antarctic (or Southern) Ocean
(b) How many oceans are there?
(c) What is the difference between an ocean and a sea?
(d) Why is the ocean blue?
(e) Why is the ocean sometimes green?
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1.3 ACTIVITIES
ANSWERS
(a) Find and label the world’s oceans:
 Pacific Ocean
 Atlantic Ocean
 Indian Ocean
 Arctic Ocean
 Antarctic (or Southern) Ocean
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1.3 ACTIVITIES
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1.3 ACTIVITIES
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(b) How many oceans are there?
There is just one ocean on Earth but there are many ways to divide it. Many scientists think there are 5
oceans (Pacific, Atlantic, Indian, Arctic and Antarctic (or Southern) Oceans) while others further divide
the Pacific and Atlantic Oceans into North and South Pacific and North and South Atlantic. Thus,
depending on your view, there may be 1, 5, or 7 oceans!
(c) What is the difference between an ocean and a sea?
An “ocean” is a very large body of saltwater while a “sea” is a much smaller body of saltwater that is
considered part of its closest ocean. Thus, the Coral Sea is considered part of the Pacific Ocean while
the Caribbean Sea is considered part of the Atlantic Ocean. The term "sea" is often given to a saltwater
area on the margins of an ocean (e.g. the Mediterranean Sea is beside the Atlantic). A sea is also often
enclosed or partially enclosed by land while an ocean is on the margin of land. The difference is not
precise and there are exceptions to the general definition.
(d) Why is the ocean blue?
The ocean generally looks blue because seawater does not absorb blue light from sunlight. When
sunlight hits the water, the blue light is scattered in all directions making it look blue.
(e) Why is the ocean sometimes green?
In seas or oceans that appear to be green, the colour is generally due to plants in the water. The
northern Atlantic and Pacific Oceans, for example, are green near the coast because of a rich
abundance of plants in the water. In contrast, the clear blue waters of the Caribbean Sea indicate the
absence or reduced number of plants.
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1.3.2 Plate Tectonics
EXTENDED ACTIVITY
(a) Find and label the following major plates in the figure below:
 North American plate
 South American plate
 Caribbean plate
 Indo-Australian plate
 African plate
 Antarctic plate
 Eurasian plate
 Arabian plate
 Iranian plate
 Pacific plate
 Nazca plate
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(b) On which plate do the Cayman Islands reside?
(c) What is the “Ring of Fire”?
(d) The spreading rate of the sea floor along the Mid-Atlantic Ridge
averages about 2.5 cm per yr (or 25 km in a million years). If the
distance between the U.S. and North Africa is currently 4,830 km,
how many years ago were they joined assuming a constant rate of
movement?
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ANSWERS
(a) Find and label the following major plates in the figure below:
 North American plate
 South American plate
 Caribbean plate
 Indo-Australian plate
 African plate
 Antarctic plate
 Eurasian plate
 Arabian plate
 Iranian plate
 Pacific plate
 Nazca plate
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(b) On which plate do the Cayman Islands reside?
Caribbean plate
(c) What is the “Ring of Fire”?
The point where two plates meet is called a “plate boundary”. Earthquakes and volcanoes are most
likely to occur either on or near plate boundaries. The "ring of fire" is a rough ring or circle stretching
from New Zealand, along the eastern edge of Asia, north across the Aleutian Islands of Alaska, and
south along the coast of North and South America. It is where the Pacific Plate interacts with other
plates such as the Indo-Australian and North American plates. Over 75% of the world's active and
dormant volcanoes are found along the ring of fire.
(d) The spreading rate of the sea floor along the Mid-Atlantic Ridge averages about 2.5 cm per yr (or 25
km in a million years). If the distance between the U.S. and North Africa is currently 4,830 km, how many
years ago were they joined assuming a constant rate of movement?
25 km = 1 million years
4,830 km = x million years
Cross-multiplying: (25 * x) = (4,830 * 1)
Therefore: x = (4,830 / 25) or 193 million years
Over the past 200 million years the Atlantic Ocean has grown from a tiny inlet of water between the
continents of Europe, Africa, and the Americas, into the vast ocean that exists today.
1.3 ACTIVITIES
1.3.3 Sea Level
CORE ACTIVITY
(a) Rising Sea Levels
Materials:
• One glass half filled with water
• One ice cube
• One marker
• Plastic cling film (to cover glass)
Method:
• Take a glass of water and use a marker to mark off the water level
• Place an ice cube in it and mark off the new water level
• Cover the glass with plastic cling film
• Allow the ice cube to melt and observe the level of the water
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(b) What happens to the water level when you add ice?
(c) What happens to the water level when the ice melts?
(d) What is “sea level”?
(e) If an iceberg is floating in the ocean and it melts as it floats
towards the tropics, will the sea
(f) What are some events that can cause sea level changes?
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ANSWERS
(a) Rising Sea Levels
Materials:
• One glass half filled with water
• One ice cube
• One marker
• Plastic cling film (to cover glass)
Method:
• Take a glass of water and use a marker to mark off the water level
• Place an ice cube in it and mark off the new water level
• Cover the glass with plastic cling film
• Allow the ice cube to melt and observe the level of the water
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(b) What happens to the water level when you add ice?
The water level rises
(c) What happens to the water level when the ice melts?
There is no change in the water level
(d) What is “sea level”?
Sea level is the average height of the ocean relative to the land
taking into account the differences caused by tides.
(e) If an iceberg is floating in the ocean and it melts as it floats
towards the tropics, will the sea level rise? Why or why not?
The sea level will not rise as the iceberg melts. The sea level will
have already risen slightly when the icecap first broke off from land
and crashed into the water (think about the experiment!)
(f) What are some events that can cause sea level changes?
• Earthquakes/Landslides
• Plate Movement
• Glaciers Melting/Freezing
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1.3.4 Sea Floor
EXTENDED ACTIVITY
(a) Find and label the following ocean floor features:
• Continental Shelf
• Ocean Trench
• Submarine Ridges / Island
• Continental Slope
• Abyssal Plain
• Continental Rise
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(b) Where is the world’s deepest trench?
(c) Where is the world’s highest mountain?
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ANSWERS
(a) Find and label the following ocean floor features:
• Continental Shelf
• Ocean Trench
• Submarine Ridges / Island
• Continental Slope
• Abyssal Plain
• Continental Rise
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(b) Where is the world’s deepest trench?
The Mariana Trench, which is located in the western Pacific Ocean
southeast of the Mariana Islands, is the deepest point on Earth. At
11,033 m (36,198 ft), the Mariana Trench is farther below sea level
than Mount Everest is above it.
(c) Where is the world’s highest mountain?
Mountains are generally measured from sea level, in which case
Mount Everest (8,848 m; 29,028 ft) is the tallest. However, Mauna
Kea on Hawaii’s Big Island rises 10,203 m (33,476 ft) from the
depths of the Pacific Ocean floor. Measuring from base to peak,
Mauna Kea is the tallest mountain on earth.
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1.3 ACTIVITIES
1.3.5 Ocean Trenches
EXTENDED ACTIVITY
(a) Find and label the following in the figure below:
• Mariana Trench (11,033 m below sea level)
• Cayman Trench (7,686 m below sea level)
• Mount Everest (8,848 m above sea level)
• Mauna Kea (4,200 m above sea level but 10,203 m tall)
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(b) Which is taller – Mount Everest or Mauna Kea? Why?
(c) True or False: If the tallest mountain on land, Mount Everest
(8,848 m; 29,028 ft), was sunk in the deepest part of the ocean – the
Mariana Trench (11,033 m; 36,198 ft) – its peak would stick out of
the water.
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1.3 ACTIVITIES
ANSWERS
(a) Find and label the following in the figure below:
• Mariana Trench (11,033 m below sea level)
• Cayman Trench (7,686 m below sea level)
• Mount Everest (8,848 m above sea level)
• Mauna Kea (4,200 m above sea level but 10,203 m tall)
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(b) Which is taller – Mount Everest or Mauna Kea? Why?
Mountains are generally measured from sea level, in which case
Mount Everest (8,848m; 29,028 ft) is the tallest. However, Mauna
Kea on Hawaii’s Big Island rises 10,203m (33,476 ft) from the
depths of the Pacific Ocean floor. Measuring from base to peak,
Mauna Kea is the tallest mountain on earth.
(c) True or False: If the tallest mountain on land, Mount Everest
(8,848 m; 29,028 ft), was sunk in the deepest part of the ocean – the
Mariana Trench (11,033 m; 36,198 ft) – its peak would stick out of
the water.
False – The peak would be covered by more than 2,000 m (7,000 ft)
of water!
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1.3 ACTIVITIES
1.3.6 Water State Transitions
CORE ACTIVITY
(a) Water can exist is several 3 forms or states. What are these states?
(b) How does water change from solid state (ice) to liquid state? What is this process called?
(c) What is Sublimation?
(d) What is Evaporation? At what temperature does freshwater boil?
(e) What is Condensation?
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(f) What is Freezing? At what temperature does freshwater freeze?
(g) Label the following figure with the following terms:
• Condensation
• Melting
• Sublimation
• Evaporation
• Freezing
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ANSWERS
(a) Water can exist is several 3 forms or states. What are these states?
• Solid – Ice
• Liquid – Water
• Gas – Water Vapour or Steam
Water is able to change between these states by the addition or removal of heat/energy.
(b) How does water change from solid state (ice) to liquid state? What is this process called?
When ice is warmed up, it changes from solid to liquid state. This process is called “melting”.
(c) What is Sublimation?
Sublimation is the process by which water changes from a solid (ice or snow) to a gas, bypassing the
liquid phase.
(d) What is Evaporation? At what temperature does freshwater boil?
Evaporation is the process by which water changes from a liquid to a gas or vapour. Evaporation occurs
when heat is added to water. Freshwater boils at 100°C (212°F)
(e) What is Condensation?
As warm water vapour cools, it forms water droplets. Condensation is the process by which water
vapour in the air is changed into liquid water.
1.3 ACTIVITIES
(f) What is Freezing? At what temperature does freshwater freeze?
As liquid water cools further, it becomes a solid (ice). Freshwater freezes at 0°C (32°F).
(g) Label the following figure with the following terms:
• Condensation
• Melting
• Sublimation
• Evaporation
• Freezing
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1.3.7 Water Cycle
EXTENDED ACTIVITY
(a) Label the Water Cycle with the following terms:
• Evaporation
• Condensation
• Precipitation
• Sublimation
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(b) Find as many water storage areas as you can
(c) What is evaporation?
(d) What is condensation?
(e) What is precipitation?
(f) What is sublimation?
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ANSWERS
(a) Label the Water Cycle with the following terms:
• Evaporation
• Condensation
• Precipitation
• Sublimation
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(b) Find as many water storage areas as you can
• Atmospheric storage
• Ice & snow storage
• Groundwater storage
• Freshwater storage (in lakes and springs)
• Saltwater storage (in oceans)
(c) What is evaporation?
Evaporation is the process by which water changes from a liquid to a gas or vapour. Evaporation occurs
when heat is added to water.
(d) What is condensation?
As warm water vapour cools, it forms water droplets. Condensation is the process by which water
vapour in the air is changed into liquid water.
(e) What is precipitation?
Precipitation occurs when so much water has condensed that the air cannot hold it anymore. The clouds
get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.
(f) What is sublimation?
Sublimation is the process by which water changes from a solid (ice or snow) to a gas, bypassing the
liquid phase.