Formation of Earth’s Oceans
About 71% of the surface of the Earth is covered by the oceans. All oceans are interconnected. The same water circulates within all of them. Initially Earth had no oceans because the surface temperature was too hot. Volcanic eruptions placed large volumes of steam in the atmosphere. These gases remained in the atmosphere for a very long time. As the Earth cooled, the steam from the volcanoes condensed and fell to the Earth as rain. The rain lasted for thousands of years and formed the first oceans.
Rainwater not only filled low lying areas but it also flowed over the land, into rivers and the oceans. As the rainwater moved across the land, it dissolved the minerals from within rocks. The process is called weathering. The dissolved minerals and solids from rocks were transported into Earth’s primitive ocean. During evaporation, the water from the ocean combined with the gases in the atmosphere to form salts. The water from the atmosphere returned back to the ocean during the water cycle. The ocean became very acidic and salty. There were great amounts of carbon dioxide in the atmosphere during the formation of the ocean. Carbon dioxide dissolves readily in water. Carbonic acid is produced when carbon dioxide reacts with water. As the levels of carbon dioxide increased in the atmosphere, the acidity of the ocean also increased. Photosynthesizing organisms helped remove some of the carbon dioxide from our ocean. The present day oceans are slightly basic and have a pH of about eight.
About 200 million years ago the Earth looked very different. There was one land mass called Pangaea and one very large ocean called Panthalassa. There are presently three major oceans. The largest ocean is the Pacific Ocean. The Atlantic Ocean is the second largest ocean followed by the Indian Ocean. Click on the videos in the sidebar to learn more about how the oceans developed on our planet.
Click on the image below to view an animation of the world seen over 600 million years.
