At a divergent plate boundary, two oceanic plates are moving away from one another. This creates new oceanic crust as magma rises from the mantle and solidifies. The gap between the two plates becomes wider over time as the new plate moves away from the boundary. The boundary can cause earthquakes and volcanic activity, and may also form features such as rift valleys and underwater volcanoes. As magma continues to be generated at the boundary, it helps to create new oceanic crust and fill the gap between the two plates.