In
plate tectonics, a
divergent boundary or
divergent plate boundary (also known as a
constructive boundary or an
extensional boundary) is a linear feature that exists between two
tectonic plates that are moving away from each other. Divergent boundaries within
continents initially produce
rifts which eventually become
rift valleys. Most active divergent plate boundaries occur between
oceanic plates and exist as
mid-oceanic ridges. Divergent boundaries also form
volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill.