Here are the outlines of the coasts and other significant topographic features. These mark the outlines of the plates ~ 15 million years ago.

Either cut along the plate boundaries, or perhaps better, use tracing paper to draw outlines and then cut out the tracings and slide back until they fit (as shown). It is best to stick the Nubia tracing to the original map first, and slide Arabia and Somalia.

Mark a series of match points on the tracing.

Slide the plates back to their original positions.

Draw lines on the original map connecting the match points Draw lines on the original map connecting the match points. You can measure these to give amount of opening that has occurred. If you print out the pdf map on A4, then 1 cm is 150 km. Alternatively, 10 degrees on the figure is ~1100 km.

To work out the future position of the plates, double the length of the join lines and mark these on the original map. You should only do this for two of the sets of lines: Nubia-Arabia and Nubia-Somalia as shown.

Now move the tracings of Arabia and Somalia, as shown, to their new positions in 15 million years time. To check that it has worked, measure the distance between the tie lines separating Somalia and Arabia and check that they have doubled in length.