Plates Separate

The Mid-Ocean Ridge and rift valleys, such as the one that runs through eastern Africa, occur along boundaries where plates are spreading apart. New oceanic crust is created as the plates separate and molten rock rises up from the mantle and fills the space. The earthquakes and the volcanic eruptions along the Mid-Ocean Ridges are a direct result of this process. (Illustration by E. Paul Oberlander, © Woods Hole Oceanographic Institution)