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.
How HD Radio Works. The radio waves that carry analog AM and FM signals are limited in the amount of information they can convey, both because of the nature of the waves themselves and the spacing of stations on the frequency band. FM stations are separated by 200 kHz, while AM stations have just 10 kHz between them. Alternate channel spacing of FM stations gives them 400 kHz to work with. The signals broadcast by radio stations are actually spread out on either side of the frequency into Upper and Lower Sidebands (USB and LSB).