Me i will make you the brainliest first you will find out how fast the seafloor is moving away from the ridge on one side. use a calculator to divide the answer to #5 by the answer to #3. round to the nearest whole number.

#5 km ÷ #3 million years = km/million years

now find out how fast the seafloor widens every 1 million years. multiply the answer you got in #6 by 2.

the seafloor spreads at a rate of km every 1 million years.

when did the seafloor start spreading?

the distance between point a and point b, or the coasts of africa and north america, is 4,550 km. using your answer to #7, find out when the atlantic ocean began to open. divide 4,550 km by your answer in #7 to find out.

4,550 km ÷ #7 = million years ago.

look at the geologic timeline. during what geologic period did the atlantic start to open?