A key or legend is used to understand symbols, colors, and shapes on a map
Well, the magma in the volcano is boiling... and boiling... and boiling, until, it finally expands enough to erupt.
This is the North Atlantic Ocean.
It can be judged by its surrounding, as it is located near the North Pole, we can deduce that it is an ocean located at the north, which could either be north Atlantic or North Pacific.
We can then use the continential plate to help us determine, which is the North America plate.
Therefore this is the North Atlantic Ocean.
Hope it helps!
