Pistol Shrimp Creates Sonic Boom

The deafening crack of a pistol shrimp's claw isn't caused by the two halves snapping together, as one might assume. Instead, the shrimp cocks its oversized claw like a hammer and fires a jet of water at over 60 miles per hour. This incredible speed creates a pocket of low pressure, a tiny vacuum bubble known as a cavitation bubble. It is the subsequent collapse of this bubble, not the initial snap, that unleashes the weapon's true power. This process of cavitation was a mystery for years, and the collective crackling of shrimp colonies was once so loud it interfered with military sonar, creating a "background noise" that could mask the sound of enemy submarines.

When the cavitation bubble collapses under the immense pressure of the surrounding water, it does so with astonishing violence. The implosion generates a shockwave and an acoustic blast that can reach 218 decibels, a level significantly louder than a gunshot. For a split second, the temperature inside the collapsing bubble soars to over 8,000 degrees Fahrenheit, nearly as hot as the surface of the sun, which creates a flash of light in a phenomenon called sonoluminescence. This powerful combination of heat, sound, and pressure is more than enough to stun or kill small fish and crabs, which the shrimp then drags back to its burrow for a meal.