The first step of seafloor spreading is when a crack forms in the oceanic crust.
Seafloor spreading occurs in ocean waters. The force behind its formation is the convection currents in the mantle beneath it. When there are more intense convection currents in the mantle, it manages to have a big influence on the crust above it and break up tectonic plates.
The first step in the seafloor spreading comes in the form of cracking up of the oceanic crust. The convection currents manage to push huge amounts of magma under very high pressure and the crust breaks up. After this happens, magma starts to rise toward the ocean floor, as it gets out in the water it solidifies, and since the process continues for millions of years, the new magma that rises is gradually pushing the rock from the older one away.
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