From our sister station WDEA in Bangor, listen as Thunder Hole at Acadia National Park erupts with the waves during gale-force winds.

When the right size wave rolls into the naturally formed inlet, a deep thunderous sound emanates. The cause is a small cavern formed low, just beneath the surface of the water. When the wave pulls back just before lunging forward, it dips the water just below the ceiling of the cavern allowing air to enter. When the wave arrives full force, it collides with the air, forcing it out, resulting in a sound like distant thunder. Water may splash into the air as high as 40 feet with a roar!"