The North Atlantic Ridge is the northern arm of the Mid-Atlantic Ridge, a mostly underwater mountain chain that runs down the middle of the Atlantic Ocean. The North Atlantic Ridge is an area where the Eurasian and North American tectonic plates are spreading apart, creating new sea floor.
The Mid-Atlantic Ridge is a continuous feature that runs from northeast of Greenland to southwest of the Cape of Good Hope in Africa. This underwater mountain chain runs for almost 10,000 miles, only breaking the surface of the ocean in a few spots. Notably, Iceland features a section of the ridge, called the Reykjanes Ridge.
The North American tectonic plate, moving apart from the Eurasian plate, creates a 'spreading' area. The ridge features this flat sea floor area, flanked by peaks on either side. As magma wells up to the spreading area, it pushes the ridges apart. The Atlantic basin is separating at a rate estimated to be from 1/2 inch to 4 inches per year.