The seafloor rocks (oceanic lithosphere) formed at centers of seafloor spreading are transported away from the mid-ocean ridges. as time passes, oceanic lithosphere moves slowly away from the spreading center at which it formed as plates continue to move and new lithosphere forms at the spreading center. in the map below, the age of oceanic lithosphere is denoted with colors. red indicates the youngest seafloor, which is less than two million years old. dark blue indicates the oldest seafloor, which is over 144 million years old. sedimentary rocks of the continental shelves are colored in light blue and are not considered part of the oceanic lithosphere.