Pillow lava is a typical product of underwater volcanic activity, with the formation of characteristic pillow-shaped structures.
When lava escapes below sea level, the outer portion cools quickly, while inside it is still completely melted and able to flow. The pressure from the inside slowly increases the size of the pillow.
Each lava pillow that escapes is superimposed on the previous one, forming platforms, like in the case of the cliff of Aci Castello.
