I was reading about mid atlantic range. This range is caused by volcanic eruptions and its responsible for continental drift by sea floor expanding.
If volcanic eruptions are there, then it will create range, i.e. magma will pile up to create range and it will spread down the slope and create thicker crust of the ocean floor. How does it push the continent ? Eruption is not some kind of force which pushes the continents with the occurrence of eruption. It will keep piling up to create the range and make crust thicker. By what mechanism is it pushing to expand the floor of the sea bed ?
Is there any other range like mid atlanic range in oceans ?

Please explain.