Ocean ridges would form. Mid-ocean ridges result from volcanic swelling and eruptions along the divergent boundary.
A landforms that forms at the plate boundary as a result of divergent stress or when two tectonic plates move apart is a mid-ocean ridge or a continental rift valley.
There are three types of plate movements: converging, transforming and diverging.
Converging plates either push together, forming mountains or subduct, one sliding under the other.
Transform boundaries are plates that push on each other as they slide in opposite directions
Divergent plates move away from each other, creating a rift in the brittle rock of the lithosphere. Divergent boundaries may occur on the ocean floor or on land. Divergent movement in ocean forms a mid-ocean ridge while a continental rift valley if it occurs on land.These geological processes of divergent boundaries shape the continents and oceans over time by forming new crust and new oceans.
The overstreching term would be an earthquake but I belive that would actually be a "Normal Fault."