1.4 Movement of Plate Boundaries

Owing to the difference in movement between the plates that are in motion, three types of plate boundaries are found to exist along their edges:

1. Spreading ridges

Spreading ridges or divergent boundaries are areas along the edges of plates move apart from each other, Figure 1.6. This is the location where the less dense molten rock from the mantle rises upwards and becomes part of crust after cooling. Highest rate of spreading or expansion between plates is found to occur near Pacific Ocean ridges and the lowest rate of spreading occurs along mid-Atlantic ridges. Generally, spreading ridges are located beneath the oceans. A few areas where the spreading occurs along the continental mass are East African rift valley and Iceland.