The Blue Planet

Ocean Formation

Learning about the formation of oceans requires that you take a fantastic journey through time. First, you will travel back to the beginning of the universe. Then, as the Earth cools, events like the eruptions of volcanoes, poisonous outgassings, and global rain storms create the Blue Planet. In this interactivity, learn about scientists' theories on how the oceans were formed. See if you understand the theories and their chronological events. Click the player button to begin.

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The Extraction of Carbon Dioxide

As you learned, the early atmosphere of Earth contained little oxygen and a lot of carbon dioxide. Today, the atmosphere contains 21 percent oxygen and very little carbon dioxide. In fact, carbon dioxide only accounts for 1 percent of all of the gases in the atmosphere. Where did all of that carbon dioxide go? The carbon dioxide in the atmosphere was removed and a large amount of oxygen was added.

The removal of carbon dioxide from the atmosphere began around a billion years ago. During this time, life evolved in the oceans that used photosynthesis. Photosynthesis uses carbon dioxide and produces oxygen as a waste product. As life flourished in the oceans, the rate of photosynthesis increased. Eventually plants evolved and even more carbon dioxide was removed from the atmosphere and oxygen in the atmosphere increased.

Flowchart showing the extraction of dissolved carbon and creation of carbonate rocks

Not all of the carbon dioxide in the atmosphere is used in the process of photosynthesis. Carbon dioxide simply dissolves in the oceans and exists as a dissolved gas. Many marine organisms use the dissolved carbon dioxide to make calcium carbonate for their shells. When these organisms die, they sink to the seabed.  Over millions of years, the buildup of their shells forms the sedimentary rock limestone. This carbonate rock contains carbon that originally came from the atmosphere. Limestone rock is found not only in the oceans but also on the continents. The existence of this rock on the continents indicates that these areas were once shallow seas.

The Earth's Oceans

Off all of the water on Earth, the vast majority is stored in the oceans. When you see a picture of the Earth from space, it appears as if the continents are surrounded by one enormous, interconnected ocean. More than 71% of Earth’s surface is covered with water; however, this water is not evenly distributed over the planet. The Northern Hemisphere is about 61% water and includes the majority of Earth’s landmasses, while the Southern Hemisphere has far less land and is about 81% water. View this activity to view the location of each ocean on Earth. Click the player button to begin.

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The Blue Planet Review

Now that you have learned about the Blue Planet called Earth, practice what you have learned. In this non-graded activity, follow the directions on each question slide. Click the player button to get started.