The Atlantic Ocean is spreading at its central part. The African and South American plates are moving away from one another. There's a mid-ocean ridge which is very active, and there's constant formation of new crust by the emerging magma from the mantle. The new crust is pilling up, and it is also pushing aside the old crust, so little by little the two plates move further apart. Apart from South America and Africa moving further away from each other, this also means that the Atlantic Ocean is becoming larger and larger every year, which is actually the only ocean at present to do so, as all the others are becoming smaller.
