How many kilometers has each ocean basin opened in the past 2 million years?

The total amount of ocean basin that has opened in the past 2 million years is approximately 160 kilometers. This number is based on the average spreading rate of the major ocean basins, which is about 2 centimeters per year. Over a period of 2 million years, this spreading rate would result in the opening of 40 kilometers of ocean basin in each ocean. This number is then doubled to account for the fact that there are two sides to each ocean basin (e.g., the Atlantic Ocean has both an eastern and western side).