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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Chapter 11 – Oceans Control the Water Cycle
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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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Chapter 11 – Oceans Control the Water Cycle
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
There are 2 types of ocean currents: Surface currents (average depth of 200m) and Deep water currents.
Causes Effects in the Ocean Type of Ocean
Current
Surface Current: A current that flows in the top 200 m of the ocean
1. Wind Action: the force of the wind blowing over the top of the water
Spin of Earth:
3. Shape of the Continents
2.
- The speed and path of the surface currents is linked to the speed and path of the wind as it moves over the water.
- 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
-
When moving water meets a solid land surface, the water is forced to flow in a different direction
Eric Hamber Secondary
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
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