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 can also occur through the process of weathering, which is the process by which sediments and rocks are broken down into soil or grains such as sand. Limestone landforms and periglacial landforms are two examples of weathering landforms.