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.
This land, when surrounded by water, is called an island. Another way an island landform can be made is through deposits of sand that came from erosion. When sand and other debris are picked up from a water current through erosion, it can be deposited in certain areas.