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Science 8
Unit 1: Water Systems on Earth
Chapter 2: Oceans Control the Water Cycle
SECTION 2.1 - OCEAN BASINS
Oceans are important because:
1. Primary water source for the water cycle
2. Control weather
3. Support diverse life
4. Provides humans with food, minerals, and resources
4 Factors That Formed Oceans:
1. Tectonic Plates
- Has helped determine where ocean basins are located.
- Tectonic plates move changing the position of the continents.
Oceans Then:
- “Panthalassa” One giant ocean 200 million years ago!
Oceans Now:
- After the continental drift.
2. Volcanic Action
- Volcanic action has built ocean floors along mid-ocean ridges in areas where plates separate.
- Has helped build continental divides in areas where plates have collided and mountain building
occurs.
- Water trapped in volcanic materials was released as vapour.
- It cooled, condensed and fell back to the earth.
- This water collected in the lowest parts of the Earth’s surface...the ocean basins.
3. Erosion
- Has aided the further development of continental drainage systems as material is removed and deposited into
the ocean basins.
4. Glaciation
- A force of erosion in the development of continental drainage systems.
- Glaciers move materials towards the oceans.
Origins of Ocean Water:
How was the water in the ocean formed?
- Oceans formed 3 billion years ago.
- Outside of Earth cooled but the inside remained hot.
- Water trapped in volcanic materials was released as vapour.
- It cooled, condensed and fell back to the earth.
- This water collected in the lowest parts of the Earth’s surface...the ocean basins.
5 Components of The Ocean Floor:
1. Mid-Ocean Ridge:
The Mid-Atlantic Ridge:
- Long, undersea mountain chains formed from volcanic
eruptions.
- They are a result of magma that has oozed up between
plates and then hardened.
- Ridges can be 1000km wide and rise up 1000-3000 above
the ocean floor.
2. Trenches:
Marianas Trench:
- Plates can’t be pushed apart forever.
- Eventually there are collisions.
- When an ocean plate collides with a continental plate,
the denser ocean plate is forced to bend down beneath
the less dense continental plates.
- Deepest trench: the Marianas Trench which is
11000 m (11km) below sea level. Mount Everest could
fit down inside it and be covered.
3. Abyssal Plains:
- Wide, open features of the sea.
- Between the high mountains ranges at the centre of the basins and the trenches of the edges are abyssal
plains.
- Formed of thick deposits of sediments.
- Where do sediments come from?
4. Continental Margins:
- Ocean basins begin many kilometres out
to sea.
- The area between the basin and the
coastline is called the continental margin.
- They are made of continental shelves and
continental slopes.
5. Continental Shelf & Slopes:
- The submerged part of the continent between
the coast and the edge of the basin.
- These shelves slope gradually away from the
land before dropping steeply downward.
- Grand Banks: this shelf is 480 km wide. Most
are only 80km!
Exploring the Ocean
1. Sonar mapping uses sound waves to probe the seabed. Sound waves are sent down from a ship to the ocean
floor and they bounce back to the surface. The time it takes for the sound wave to bounce back indicates how
deep the water is in that place.
2. Satellites in space use radar and infrared light to survey very large areas of the ocean in a short time, and
they are able to record data at any time in any weather. They give detailed pictures and are also able to predict
weather and monitor wave movement.
3. Submersibles give the most detailed information from the deepest parts of the ocean, where it is impossible
to explore the deep sea without technology. They are small, extremely strong vehicles. There are two types:
manned vehicles (carry people) and remotely operated vehicles (controlled from the ship and can stay down
longer).
4. New deep sea cameras and video are allowing pictures to be taken 6000m (6km) below the surface. Cameras
are towed from ships and they can take thousands of pictures a day. They are allowing scientists to discover
new species and explore undersea like never before.
SECTION 2.2 - OCEAN CURRENTS
What is a current?
●A large amount of ocean water that moves
in a particular and unchanging direction.
●A current flows in one direction and
connects one place with another.
●The largest current: The Antarctic
Circumpolar Current -24,000 km long.
●Currents important to Newfoundland and
Labrador: the Gulf Stream and the Labrador
Current.
Two Types of Currents:
1. Surface Currents: Flow in the top 100-200m.
2. Deep Currents: Flow below 200m.
Factors that influence surface currents:
1.WIND
 Air movement caused by uneven heating.
 The energy of the moving air is transferred by friction to the water molecules causing it to move.
2. EARTH’S ROTATION
 The Earth spins counter-clockwise.

This spinning body deflects winds and currents depending on what side the equator they are on.

This alteration of direction is called the Coriolis Effect.
- Clockwise in the Northern Hemisphere and Counter clockwise in the Southern Hemisphere.
3. SHAPE OF CONTINENTS
 Moving currents are forced to turn when they meet a solid surface.
 Currents flowing N/S will deflect E/W
 Currents flowing E/W will deflect N/S
Factors Effecting Deep Currents are:
1. TEMPERATURE
 Not the same at every depth.
There are three different temperature layers:
a) Surface (mixed) layer
b) Thermocline
c) Deep Water



Cold water has a higher density than warm water.
As a result cold water will sink creating a movement of water.
This is a density current.
2. SALINITY
 Seawater is less salty at the mouths of large rivers due to the fresh water entering the ocean.
 Fresh water also enters where glaciers and icebergs melt and areas of high precipitation.
 High amounts of evaporation increases salinity as well as freezing.
Water will high salinity is denser that water with lower salinity and will sink thus creating a movement
of water. This creates a density current.
Some Local Ocean Currents:
1. The Labrador Current: Cold water
2. The Gulf Stream:
Warm water
SECTION 2.3 - WAVES AND TIDES
Ocean Waves
 Large ripples set in motion by steady winds.
 Waves on the surface of water are the result of a transfer of energy from moving air to the water.
 As a wave approaches a shoreline the wave length decreases and the wave height increases.
Draw this diagram:
Swells
Smooth waves caused by wind and storms far out in the ocean.
Breakers
The tumble of water when a wave collapses onshore.
Tsunamis
Giant waves that can be sent in motion by earthquakes on the
ocean floor, landslides or volcanic eruptions near the shoreline.
Ex. Newfoundland’s Burin Peninsula in 1929
Shaping Our Shorelines
 Waves have the power to erode and deposit sediments on
the shore.

Tides work with waves to determine the range of
shoreline that can be affected by wave action.

Wave energy is concentrated on headlands and spreads
out as it reaches bays.
Factors that affect the interaction of waves and tides on the shorelines are:
1) Slope of the shoreline
2) Shape of the shoreline
3) Type of rock material
4) Wave energy
What are Tides?
The slow rise and fall of the ocean.
 The upper and lower edges of a beach are determined
by the high- and low- tide mark.

Tides are connected to the motion of the moon and
the spinning of the Earth.

The moon exerts a greater force of pull than the sun
due to its closer proximity to Earth.
Two Types of Tides:
1.
Spring Tide:
 Occur when the Earth, Sun and Moon are in a line.
 Causes extra high and low tides.
2.
Neap Tides:
 Occur when the Sun and the Moon are at right
anglesto one another.
 Causes the smallest tidal movements. There is little
difference between low and high tides.
Tidal Range
- The difference in level between a high and a low tide.
The shoreline can change very quickly due to intense
wave action during:
 winter storms
 hurricanes
 tsunamis
Technologies to prevent or reduce the effects of wave action near human development include:
1. Breakwaters
2. Jetties/Wharves
3. Vegetation
4. Sea walls
5. Coastal reconfiguration