How do rocks along the central valley of the mid oceanic ridges provide evidence of seafloor spreading?

These rocks allow you to know the ages of the rocks. If the rocks are farther from the ridge, they are considered old. The rocks near the ridges are considered the young rocks. Aside from the rock ages, it also helps determine the Earth's magnetic field. Scientists can determine this one with the help of the iron substances in the sea floor. It also helps determine the movements of active volcanoes and heat flow of the lave with the use of MOR

That depends on what kind of environ meant it is in  in space it has the same force that was applied when the velocity was gained