A typical rate of seafloor spreading in the atlantic ocean is .

About 2 cm per year.

Explanation:

The Atlantic ocean's seafloor is known to be part of the mid-Atlantic ridge which is a mid-ocean ridge whose inherent properties causes it to have a slow spreading nature.

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )