When ocean waves travel toward the coast, most of the energy is absorbed gradually by a beach. But at Boca do Inferno, the waves rush into a gap in the hard volcanic rock where they have nowhere to go. All that energy gets pushed upward through a small opening, sending a powerful jet of foaming seawater shooting into the air - sometimes as high as a house.
This type of natural feature is called a blow-hole. It works a bit like squeezing a tube of toothpaste - if you block most of the opening, the paste has to come out of the little gap much more forcefully. The sea does the same thing with the waves.
The sound at Boca do Inferno is extraordinary. Even before you see the blow-hole, you can hear a deep booming sound echoing off the rocks as each wave pushes through. Visitors stand at a safe distance and watch the spouts in surprise, especially when a particularly big wave sends water flying higher than expected.
The dramatic name came from local fishermen who noticed how powerful and unpredictable the churning water looked. Despite the name, it is a beautiful and popular place to visit, and many people come in the early morning when the light makes the white spray sparkle.