In sea-floor spreading, molten material rises from the mantle and erupts in the...

along mid ocean ridges

Explanation:

In 1960, Harry Hess came up with the discovery that the floor of the oceans undergoes a movement. This movement is similar to that of being a conveyor belt. In this movement, continents are moved along with the oceans. The molten materials moves up to the mid-ocean ridge where it spreads and erupts. In this process the molten materials pushes the rocks sideways thereby emerging out from the mantel. The freezing of the molten material formed new rocks. This process is termed to be sea-floor spreading.