VIDEO LESSON

LESSSON OBJECTIVES

By the end of this lesson, you will be able to:

• Explain Continental Drift Theory
• Compare the sizes of landmasses and oceanic basins over the globe
•  Locate the current positions of Continents and Oceanic basins.

BRAINSTORMING QUESTIONS

• How were the continents formed?
• How were they separated from the Pangaea?
• What is continental drift? How does it happen?

Dear Online Learner! The surface area of the Earth is estimated to be 510,072,000 km² and the area of the Oceans is about 363, 000,000 km².

• All water covers greater than 71% of Earth’s surface.
• Oceans account for over 97% of all the water on Earth.
• Glaciers and polar ice caps contain greater than 2% of the Earth’s water.
•  Only about 0.6% is found under the surface as groundwater.
• Nevertheless, groundwater is 36 times more plentiful than water found in lakes, inland Seas, rivers, and in the atmosphere as water vapor.

The distribution of Ocean basins and Continents is unevenly arranged over the Earth’s surface. In the Northern Hemisphere, the ratio of land to ocean is about 1:1.5. But it is 1:4 in the Southern Hemisphere. The greater abundance of water is in the Southern Hemisphere.

The Continents

Dear Online Learner! A continent is a huge area of land mostly separate by a water body. There are seven known continents on the earth today. They are: Africa, Antarctica, Asia, Australia, Europe, North America, and South America.

Africa

• The second largest continent in the world next to Asia.
• The equator divides Africa into two parts.
• The largest part of the continent is found north of the equator.
• It is the only continent crossed by the equator, Tropic of Cancer, and Tropic of Capricorn.
• The world’s largest hot desert (Sahara) and the world’s longest river (River Nile) found.

Antarctica

• Permanently ice covered continent located around the South-Pole.
•  There are no permanent human settlements in Antarctica.
• But, many countries have research stations in Antarctica.

Asia

• The largest continent in the world.
• Covering one-third of the total land area of the earth.
• Crossed by the Tropic of Cancer and separated by the Ural Mountains from Europe.  
• Bounded by water bodies on three sides and by the Pacific Ocean in the east and southern part.
• Asia has 48 countries and accommodates two-third of the world population.
•  It has the highest mountains (Himalayas), the deepest depressions (Dead Sea), the driest desert (Lut desert), highest precipitation (Assam) and long tradition of civilization (Mesopotamia).

Australia

• The smallest continent in the world.
• Surrounded by water in all of its sides and often called an Island continent or Oceania.
• It is the driest inhabited continent in the world with 70 percent of it either arid or semi-arid.
• The vast majority of its population is concentrated along the eastern and south-eastern coasts.
• Entirely lies in the southern hemisphere.

Europe

• The second smallest continent in the world, and home of the industrial revolution.
• It has 44 countries. It lies to the west of Asia and north of Africa.
• Bounded by the Atlantic and Arctic oceans and by the Mediterranean Sea in the south.

North America

• Located west of the Atlantic Ocean and linked to South America by the narrow strip of land called the Isthmus of Panama.
• It is the third largest continent of the earth.
• Surrounded by the Atlantic, Pacific and Arctic Oceans.

South America

• Bounded in the east by the Atlantic Ocean and in the west by the Pacific Ocean.
• The world’s largest River (Amazon River), largest and most bio-diverse rainforest, tallest uninterrupted waterfall (Angel Falls) and the north-south extending longest mountain (Andes Mt.) are found.  
• South America has 12 countries.

Oceans

Geographers have divided named the interconnected oceans of the world in to five groups

The Arctic Ocean

• It is the world’s smallest Ocean with an area of 14,056,000 km².
• Lies in the area between Europe, Asia, and North America.
• Its average depth is 1,205 m.
• Most of the year, much of the Arctic Ocean is covered by a drifting polar icepack that is an average of 3 m thick.

The Atlantic Ocean

• The world’s second-largest Ocean with an area of 76,762,000 km².
• Located between Africa, Europe, and the Southern Ocean
• Contains the majority of the Earth’s shallow Seas, but relatively few islands.
• E.g. Baltic Sea, Black Sea, Caribbean Sea, Gulf of Mexico, North Sea, and the Mediterranean Sea.
• The average depth of the Atlantic Ocean is 3,926 m. Its deepest point is the Puerto Rico Trench which is some 8,605 m deep
• The Amazon, Mississippi, St. Lawrence, and Congo rivers discharge to it. It receives more freshwater from continental runoff than any other Ocean basin.
• Important to the world’s weather (as are all oceans).

Figure 1.10 Continents and Oceans of the World

The Indian Ocean

• The world’s third-largest ocean and it has an area of 68,566,000 Km².
• Located in the area between Africa, the Southern Ocean, Asia, and Australia.
• Has an average depth of 3,963 m. Its deepest point is at the Java Trench or Sunda Double Trench.
•  The maximum depth reaches some 7,258 m.
• The waters of the Indian Ocean also include Andaman, Arabian, Flores, Java, and the Red Sea as well as the Bay of Bengal, Great Australian Bight, Gulf of Aden, Gulf of Oman, Mozambique Channel and the Persian Gulf.
• Is known for causing the monsoon weather patterns that dominate much of Southeast Asia.

Figure 1.11: Trenches (deepest parts of the Oceans)
Source: www.trenchesandtrenches.weebly.com

The Pacific Ocean

• By far the world’s largest ocean basin with about 155,557,000 km².
• It covers 28% of the Earth and is equal in size to nearly all of the land area on the Earth combined.
• Located between the Southern Ocean, Asia, and Australia.
•  Has an average depth of 4,028 meters, but its deepest point is the Challenger Deep within the Mariana Trench , about 10,924 m deep.
• This area is also the deepest point in the world.
• The Pacific Ocean has few marginal Seas but many islands. It is an important for it’s major historical route of exploration and migration.

The Southern Ocean

• The world’s newest and fourth-largest Ocean.
• In the spring of 2000, the International Hydrographic Organization decided to delimit it as the fifth Ocean.
•  Boundaries taken from the Pacific, Atlantic, and Indian Oceans.
• Extends from the coast of Antarctica to 60 degrees south latitude.
• Has a total area of 20,327,000 km² and an average depth ranging from 4,000 to 5,000 m.
• The deepest point in the Southern Ocean is unnamed, but it is in the south end of the South Sandwich Trench and has a depth of 7,235m.