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.
Fjords, glaciated valleys, and horns are all erosional types of landforms, created when a glacier cuts away at the landscape. Other types of glacial landforms are created by the features and sediments left behind after a glacier retreats. When glaciers retreat, they often deposit large mounds of till: gravel, small rocks, sand, and mud. It is made from the rock and soil that was ground up beneath the glacier as it moved. Material a glacier picks up or pushes as it moves forms moraines along the surface and sides of the glacier.