Surf Science – What Makes a Wave Spit?- FEB 01, 2018
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Pulling into a wide-open barrel is one of the most euphoric moments for a surfer. Time stands still as you race through your very own aquatic cylinder of joy, encapsulated by a room of moving water. Perhaps the only feeling that rivals pulling into the barrel is immediately coming out afterwards, your body tingling from the wave spitting behind you.
From the beach, a spitting wave may go unnoticed to the untrained eye. But to a seasoned surfer, spitting waves can be anticipated before the wave itself even starts to break. It’s a weird kind of sixth sense that is only acquired by analyzing thousands of individual breaking waves. Not quite a superpower, but pretty close!
So let’s explore … what makes a wave spit?
As a wave breaks from top to bottom and creates a hollow barrel within, a mixture of foam and spray is created from the falling lip, impacting the ocean surface below. Most of the foam immediately turns into white water in front of the wave, and fizzles out as it propels towards the beach. A smaller percentage of foam and spray is steadily collected within the hollow tubing section of the wave. As the wave stays open and swiftly barrels down the wave face, more and more air and spray is being accumulated within the barrel. At a critical point when the pressure becomes too high for the limited space within the barrel, the air and spray are discharged by taking the path of least resistance and “spitting” out the open end of the wave.
The physics are very similar to shaking a bottle of carbonated beverage or champagne. As air is released within the limited-sized bottle, the pressure inside accumulates to a critical point where it must be released. The bottle will either explode, or you can remove the cap or cork to relieve the pressure. Either way, air and foam will come spewing out through the path of least resistance.
So do all barreling waves spit? The answer is no. Only waves that break swiftly and maintain an open barrel will spit. The idea is to raise the pressure inside the barrel very abruptly so there is more force to expel the air. Furthermore, not only big waves have the ability to spit. Waves as small as one foot can spit, as long as the pressure gets high enough within the confined space.
See you out in the water!