1. Unit 1: Water Systems on Earth Chapter 2: Oceans
Science 8
Unit 1: Water Systems on Earth Chapter 2: Oceans
Section 2.1: Ocean Basins
Slide Show #4

2. Section 2.1: Ocean Basins Origin of the Oceans
Science 8
Section 2.1: Ocean Basins Origin of the Oceans
How were the oceans formed?
Over 200 million years ago, all the continents were together in one large land mass called Pangea.
The rest of the Earth was covered by one giant ocean called Panthalassa.
Chapter 2: Oceans

3. Section 2.1: Ocean Basins Origin of the Oceans
Science 8
Section 2.1: Ocean Basins Origin of the Oceans
Slowly, Pangea began to split up in a process called plate tectonics.
The Earth’s surface is made up of large, slow moving rocks called tectonic plates.
Chapter 2: Oceans

4. Section 2.1: Ocean Basins Origin of the Oceans
Science 8
Section 2.1: Ocean Basins Origin of the Oceans
How did these huge sections of rock move?
Although the rock sections are solid, they float over a layer of molten rock (liquid rock) called magma.
Chapter 2: Oceans

5. Section 2.1: Ocean Basins Origin of the Oceans
Science 8
Section 2.1: Ocean Basins Origin of the Oceans
Process of plate tectonics:
Magma heats up from the energy in the Earth’s core.
Molten rock rises.
This increase of pressure causes two plates to break apart.
Over millions of years, large land masses can move into different positions.
See videos from Aliant Learning Center.
Within this site, search for “plate tectonics”.
Chapter 2: Oceans

6. Section 2.1: Ocean Basins The Origin of Ocean Water
Science 8
Section 2.1: Ocean Basins The Origin of Ocean Water
Where did our ocean water come from?
Some scientists believe the following theory:
Our Earth began as a hot ball of molten rock.
As the Earth’s surface began to cool down, heat continued to be released through volcanoes.
Within these volcanoes, water was trapped and then released as water vapour during an eruption.
As the water cooled and condensed, it fell as precipitation.
Through run-off (caused by gravity), the water collected in the lowest parts of the Earth’s surface – ocean basins.
Chapter 2: Oceans

7. Section 2.1: Ocean Basins The Origin of Ocean Water
Science 8
Section 2.1: Ocean Basins The Origin of Ocean Water
Another theory held by some scientists is that our ocean water came from ice in comets that hit the young Earth.
National Geographic has a great video about the origins of our ocean water. The link is given below:
National Geographic and in the search menu, type “origin of the oceans”.
Chapter 2: Oceans

8. Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.43)
Science 8
Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.43)
You might be surprised by the fact that the features of the ocean floor are very similar to those found on land.
The ocean basins contain mountain ranges, deep valleys, and wide plains.
How did these formations get here?
Chapter 2: Oceans

9. Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.44)
Science 8
Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.44)
Ocean Ridges: Undersea mountain chains formed from hardened magma that escaped when two plates were pushed apart.
Also see Figure 2.6 on page 44.
Chapter 2: Oceans

10. Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.44)
Science 8
Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.44)
Trenches are deep valleys in the ocean floor.
These are formed when an oceanic plate collides with a continental plate. The denser ocean plate is forced to bend steeply down beneath the less dense continental plate.
Chapter 2: Oceans

11. Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.45)
Science 8
Section 2.1: Ocean Basins A Journey on the Ocean Floor (p.45)
Abyssal Plains are wide, open, flat features of the deep sea.
They are formed from thick layers of sediment.
The sediments reach the sea floor by great underwater landslides (caused by earthquakes, gravity and ocean currents).
Chapter 2: Oceans

12. Section 2.1: Ocean Basins Continental Margins (p.45)
Science 8
Section 2.1: Ocean Basins Continental Margins (p.45)
Ocean basins do not begin at the coastline but rather many kilometers out to sea.
The area between the basin and the coastline is called the continental margin.
These margins are made up of the:
Continental shelf
Continental slope
Chapter 2: Oceans

13. Section 2.1: Ocean Basins Continental Margins (p.45)
Science 8
Section 2.1: Ocean Basins Continental Margins (p.45)
Continental Shelf
The submerged part of the continent between the coast and the edge of the basin.
They slope gradually away from the land before dropping steeply downward at the shelf edge.
Chapter 2: Oceans

14. Section 2.1: Ocean Basins Continental Margins (p.45)
Science 8
Section 2.1: Ocean Basins Continental Margins (p.45)
Continental Slope
The steep slope at the edge of the continental shelf.
Beyond the base of the continental slope lies the floor of the ocean basin (abyssal plain).
Chapter 2: Oceans

15. Section 2.1: Ocean Basins Exploring the Oceans (p.46)
Science 8
Section 2.1: Ocean Basins Exploring the Oceans (p.46)
There are many different ways that scientists explore the ocean floor. Do you recognize any of the following methods?
Sonar Mapping
Satellites
Submersibles
Deep Sea Cameras and Video
Chapter 2: Oceans

16. Section 2.1: Ocean Basins Exploring the Oceans (p.46)
Science 8
Section 2.1: Ocean Basins Exploring the Oceans (p.46)
In your textbooks, complete a KWL chart for these methods of exploration.
We will be doing a research project on these methods. See your teacher for details!!
Chapter 2: Oceans

17. Section 2.1: Ocean Basins Assignment
Science 8
Section 2.1: Ocean Basins Assignment
You will be given the chapter 2 assignment in 3 parts – 1 part per section.
It is recommended to complete each part as you finish the section so that you do not have to finish them all at once!!
Assignment #2 (Part A):
Page 51: #1 – 11
Q: Write a paragraph describing one of the methods for ocean exploration that you researched.
Chapter 2: Oceans