How and when was the Atlantic Ocean formed?

Mustahsan's answer is great. Here are a few sites if you want to do some additional reading: North Atlantic breakup (wikipedia) Ancient Earth (App for exploring history of plate motions) Paleomap Project (includes animations, paleomaps, teaching ... read more

Atlantic was not on the face of the Earth until 130 million years ago. When Pangaea start spiting apart, water from Panthalassa (Ancient super-ocean) started filling the gaps formed between African Plate and South American plate forming the Atlantic we see today. read more

Atlantic Ocean. The Atlantic Ocean is the second largest of the world's oceans with a total area of about 106,460,000 square kilometers (41,100,000 square miles). It covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. read more