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 Created by Weathering, Erosion, & Deposition. The animation on the page shows how karst topography is formed by the chemical weathering process of carbonation. For a complete review of karst topography and the formation of caves & caverns, review the page titled EXPLORE: Karst Topography in Chapter 11.2.