Imagine that you could dive deep into the Atlantic Ocean where the South American plate and African plate meet at a plate boundary. What do you think you would see at the plate boundary? Would you see the mantle? Why or why not?

At the plate boundary, there would be a divergent boundary where we can see a mid ocean ridge and a gap. We would be able to see the mantle because there would be a fissure from where magma will rise and solidify.    

Explanation:

Under the South American plate and African plate, there are currents that cause a divergent boundary. They create this boundary since they pull the tectonic plates apart, causing a mid-ocean ridge with an opening that allows the rising of the magma that was underneath. Once that the magma is out, it solidifies, and the currents will try to create another ridge to repeat the process.

When the plates are apart, the mantle that is beneath is exposed, and we can see the magma.