Frequent eruptions along divergent plate boundaries such as the Mid-Atlantic Ridge form new ocean bottom in a process known as seafloor spreading. This process occurs slowly (1-15 centimeters per year) yet relentlessly, moving the plates—and the ocean floor and continents above them—further apart.olcanoes are common occurrences along the boundaries of Earth’s tectonic plates. These boundaries allow super-heated molten rock called magma, along with ash and gases, to rise through Earth’s crust and emerge on the surface, often dramatically.