HELP!!!! GEOLOGY ? ABOUT SEA FLOOR SPREADING!?

Well you have to have some information about the sea floor, right? Like maybe a map showing magnetic reversal lines on the ocean floor. The map would have to show some feature and tell you how old it is - then you just measure how far it is on the map to the another spot where you know the age and divide that distance by the time it took to move from one spot to the other.