Consider that since mid-1982, the Lincoln Cent has been made from a zinc planchette with thin copper plating. Since zinc is very reactive compared to copper, any compromise of the plating will expose zinc to oxidation. Normal circulation can do this, but yours has obvious post mint damage.
The copper plating gets compromised by a pin hole and the zinc deteriorates from the inside. As the zinc oxidizes it expands slightly which pushes and distorts the copper outward, giving the volcano effect.