Download BC Science 8 - Chapter 11

BC Science 8
Chapter 11 – Ocean Control the Water Cycle
11.1 Ocean Basins
 Over 2.3 of Earth’s surface is covered by oceans
 5 major oceans are: Pacific, Atlantic, Indian, Southern, and Arctic.
The Southern Ocean includes all the southern portions of the
Pacific, Indian, and Atlantic Oceans.(completely surrounds
Antarctica)
 Basins are the low points on Earth’s surface. Oceans are basins into
which water has flowed and accumulated.
 Oceans control Earth’s temperature, create weather patterns, and are
the source of the water that falls as fresh water on land, supporting
all life forms.
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The Origin of Ocean Water
 Oceans have been on Earth for more than 3 billion years. (scientists
believe)
 Earth first formed about 4.5 billion years ago, starting as a ball of
melted rock
 The outside of Earth cooled down, but heat continued to be released
from within the planet through volcanoes.
 Water trapped inside the volcanic materials was released into the
atmosphere in the form of water vapour; as the water vapour cooled
and condensed, it fell to Earth’s surface as precipitation.
 Gravity causes water to flow downhill, and the vast amount of water
began collecting in the lowest parts of Earth’s surface, the ocean
basins.
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Features of the Ocean Floor
 The ocean floor has mountain ranges, valleys, flat plains, canyons,
and volcanoes and they all tend to be much larger than similar
features on land.
 The ocean floor has 2 distinct parts: The Ocean basin, (largest)
and the Continental Margins (rising outside edges)
Ocean Basins
 The forces that shape landforms such as wind, rivers, rain, or ice do
not occur under the ocean; however storm waters can erode coral
reefs, and icebergs can gouge deep grooves in the ocean floor.
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 The main force that shapes the ocean basins is the movement of
Earth’s crust.
 Earth’s crust is made up of large sections of rock called tectonic
plates.
 These solid plates float over a layer of molten rock (magma), and as
the magma heats up from the heat energy in Earth’s core, the molten
rock rises.
 This pressure can force 2 plates apart.
 There are 2 types of tectonic plates: oceanic (plates that lie under
the bottom of the ocean, and continental (those that lie under
continents.
 The movement of the plates and the way they interact are called
tectonic processes.
 A Mid-Ocean Ridge occurs when 2 plates are pushed apart, and the
underlying magma oozes up into the empty space. (ex. Mid-Atlantic
Ridge)
 An ocean trench is formed when an oceanic plate collides with a
continental plate, and the denser oceanic plate is forced to slip
underneath the continental plate. (known as subduction)
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 Abyssal plains are the wide, flat areas stretching between the areas
of trenches and mid-ocean ridges, and make up about 30% of the
Atlantic Ocean floor and over 75% of the Pacific Ocean floor.

seamount is an old inactive volcano underwater that once
developed near a mid-ocean ridge, but has been shi8fted away as
the plates move apart.
Continental Margins
 Continental Margins are the regions of the ocean floor that lie
underwater along the edge of the continents.
 The Continental Shelf is a flat area that extends from the continent’s
shoreline to the ocean basin.
 The Continental Slope is a steep area that drops off rapidly to the
ocean basin from the edge of the continental shelf. (ex. The Grand
Banks)
 The Continental Rise is a gentle slope at the base of the Continental
Slope formed by sediments carried by turbidity currents, which are
underwater landslides from the continental slope.
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 Submarine Canyons are deep gullies carved in the continental
shelf and continental slope by powerful turbidity currents.
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11.2 Ocean Currents

An Ocean Current is a large mass of ocean water that moves in a
single direction through the ocean.

There are more than 20 major ocean currents in the world that
transport dissolved minerals, solar energy, oxygen, carbon dioxide, fish
and plankton (microscopic plants and animals)
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
There are 2 types of ocean currents: Surface currents (average depth
of 200m) and Deep water currents.
Type of Ocean
Current
Causes
Effects in the Ocean
Surface Current: A
1. Wind Action: the force of the wind
- The speed and path of
current that flows in
the top 200 m of the
ocean
blowing over the top of the water
the surface currents is
linked to the speed and
path of the wind as it
moves over the water.
2.
Spin of Earth:
- As wind and water flow
over Earth’s surface,
Earth spins under them
from west to east.
(counter clockwise) This
pushes currents in the
northern hemisphere to
the right (east). In the
southern hemisphere,
currents are pushed to the
left (west) This
alteration of direction is
called the Coriolis
Effect
3. Shape of the Continents
- When moving water
meets a solid land
surface, the water is
forced to flow in a
different direction
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Chapter 11 – Oceans Control the Water Cycle
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Eric Hamber Secondary
Chapter 11 – Oceans Control the Water Cycle
Learning Strategies Centre
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Eric Hamber Secondary
Chapter 11 – Oceans Control the Water Cycle
Learning Strategies Centre
10