Explanation:

Constant eruptions at the crest of oceanic ridges cause the rupture of the oceanic crust and the new lava wedges into it, pushing the oceanic crust on either side. The ocean floor, thus spreads, known as sea floor spreading.
Sea floor spreading is verified using these phenomena:
? It was realised that all along the mid-oceanic ridges, volcanic eruptions are common and they bring huge amounts of lava to the surface in this area. The sediments on the ocean floor are unexpectedly very thin.
? The age of the rocks increases as one moves away from the crest.
? The ocean crust rocks are much younger than the continental rocks.
? The sediments on the ocean floor are unexpectedly very thin.
? The deep trenches have deep-seated earthquake occurrences while in the mid-oceanic ridge areas, the quake foci have shallow depths. It means lava is in close vicinity.