Because the contact area between two subducting plates is massive (hundreds of kilometers long and wide), it can store an incredible amount of elastic energy. When this “megathrust” finally slips, the energy release is equivalent to thousands of atomic bombs. All of the top 10 largest earthquakes in recorded history, including the 1960 Chile (9.5) and 2011 Japan (9.1) quakes, were megathrust events. These boundaries are also unique because they involve vertical seafloor movement, making them the primary source of trans-oceanic tsunamis.