Basically, a passive radiator is a reactionary device as the name suggests. When a driver (such as a subwoofer) is mounted to a sealed speaker box (enclosure), the physical forward/back movement of the speaker affects the internal air pressure of the enclosure.
Three landforms created by wind are; sand dunes, yardangs (half-teardrop shaped formations hill sized, and deflation hollows (wind swept depressions.
Erosion and deposition are responsible for many landforms. Erosion is the transport of sediments. Agents of erosion include flowing water, waves, wind, ice, or gravity. Eroded material is eventually dropped somewhere else.