Glaciers advanced from Canada and retreated four or more times. Over a few million years, Puget Sound was carved and scoured by glaciers. Heavy Pressure. Glaciers containing up to 2,383 cubic miles of ice pushed over the Puget lowland.
AM stands for amplitude modulation, while FM stands for frequency modulation. In AM, the amplitude (the height or depth of the crests or troughs) changes, while in FM, the fre â¦ quency changes. Answered.
Audience. The vast majority of Americans still report listening to AM/FM radio weekly. But, as many as 40% percent of Americans now listen to audio on digital devices, and that is projected to double by 2015, while interest in traditional radioâeven the HD optionâis on the decline. One of the prime arenas for digital listening was the car, once the domain of AM/FM radio.