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.
Landforms are defined as the natural physical features found on the surface of the earth created as a result of various forces of nature such as wind, water, ice, and movement of tectonic plates. Some landforms are created in a matter of few hours, while others take millions of years to appear.