Why is the Mid-Atlantic Ridge spreading slower than the East-Pacific Rise?
First we must look at the different type of actions taking place at these two sections of the earth. On the East-Pacific Rise, the eastward moving Cocos and Nazca plates meet the westward moving South American Plate and the North American Plate and are being sub-ducted under them. In other words, one plate is going under the other which amounts to a, as you put it, spreading. Whereas the in the mid-Atlantic ridge is a zone of constant uplifting. The European plate and the North American plates are ramming into each other (versus sliding against each other e.g the San Andreas fault or sub-ducting e. g. the Cocos and Nazca plates) forcing the crust “up” which in geologic terms is not spreading at all but forcing the earth’s crust in an upwards state. Hence the term “ridge”. This ridge has deep valleys which are constantly being filled in with magma as they push up and volcanism is taking place deep below the bottom of the Atlantic Ocean. (Iceland is in this zone which can be identified b
