The Pacific Ocean is the largest and deepest of the world's oceans and also the oldest of all existing ocean basins. The rocks within the basin date about 200 million years old. Plate tectonics was a major phenomenon in shaping the features of the Pacific Ocean basin. The colliding of plates within the Pacific Ocean has created earthquakes and volcanoes that give the Pacific basin the name "Ring of Fire."
The second largest ocean is the Atlantic Ocean. Because of extensive ship traffic between Europe and North America, the Atlantic Ocean is the most heavily traveled and most intensely studied ocean. The Atlantic Ocean consists of two parts; North Atlantic and South Atlantic. The Atlantic Ocean started to form during the Jurassic period when a rift opened up, which resulted in separation of South America and Africa. There are three large basins on the American side, which are more than 5,000 meters deep. On the European-African side, there are several smaller basins, equally as deep.
The third largest ocean is the Indian Ocean. There are no natural boundaries separating the Indian and Atlantic Oceans. The Indian Ocean is approximately 26 million square miles. The Indian Ocean basin averages about 4,210 meters. However, the deepest part of the basin reaches a depth of more than 7,258 meters. The Mid-Indian Ocean Ridge divides this basin in half.
The fourth largest ocean is the Antarctic or Southern Ocean. This ocean has the distinction of being within a polar region, completely encircling the Antarctica. The ocean is approximately 7 million square miles.
The smallest of the five oceans is the Arctic, which is approximately 5.5 million square miles. Continental shelves make up one-third of the ocean. The Arctic Basin proper consists of four basins and three parallel ridges.The Arctic Ocean is about 1,500 meters deep because of the vast shallow expanses of the continental shelves. However, the deepest part is about 5,450 meters.