How does the observed change in sea-floor age support the theory of sea-floor spreading?

The seafloor is younger at the mid-ocean ridge, and as it gets further away from it is older and older.

Explanation:

The seafloor and its characteristics is one of the best evidence when it comes to the theory of plate tectonics. This was first noticed by Alfred Wegener and later by any other scienticsts that have been interested in this theory. Basically, the evidence lies in the fact that the seafloor is the youngest at the active mid-ocean ridge, and the further it is from it it gets older and older, with the oldest seafloor being found at the subduction zones.

The reason for this is the manner in which the seafloor forms. The high activity in the mantle below manages to break the crust of a preexisting plate and divide it. It pushes enormous amouns of magma toward the surface constantly for millions of years. The magma quickly solidifies and creates new seafloor as it gets in touch with the water. The magma that comes through pushes the already consolidated one aside and the process goes on for millions of years.