Atlantic sea-floor spreading activity 2.6 the map of the northers atlantic ocran basin g az) of equal age) of the basaltic e the sediments that have accumulased on the seafloor thse sochuroms were derived by maria scton and her olgues (012) from an analysis of marine magnetic anomalics, and their ages are based on the gromagnetic polariey time scale. gat htp: /) was used to make this map. the red line on the map shows the location of the divergent boundary-the asis of the mid ocean dge between the north american and african plat north american plate african plate 154.3 myr (m25) figure a2.6.1 the approximate great-circle distances between the points identified on the map are listed here. the uncertainty in the distances provided is probably on the order of 10 km. 1354 km 1338 km 1320 km 279 km to a cup to a b to b 2017km 2509 km 2649 km 5107 km to b bay to a i. what is the average speed at which a drifted away from the ridge at a during the past 67.7 myr expressed in cm/y what is the average speed that baf drifted from a2-- -cm/yt. which plate moved faster relative to the ridge over the past 67.7 myr, if either? 2. the area between cu and bu consists of oceanic lithosphere added along the mid-atlantic ridge to the north american plate between 154.3 and 67.7 myr. what is the average speed at which new lithosphere was added to the north american plate along that line? do the same analysis for the lithosphere between points car and bar what is the average speed at which new lithosphere was added to the african plate along that line? cm/y which plate moved faster relative to the ridge between 154.3 and 67.7 myt, if either? cm/yr. 65