Earth tide Earth tide Earth tide (also known as solid Earth tide, crustal tide, body tide, bodily tide or land tide) is the displacement of the solid earth's surface caused by the gravity of the Moon and Sun. Its main component has meter-level amplitude at periods of about 12 hours and longer. The largest body tide constituents are semi-diurnal, but there are also significant diurnal, semi-annual, and fortnightly contributions. Though the gravitational forcing causing earth tides and ocean tides is the same, the responses are quite different. The larger of the periodic gravitational forces is from the Moon but that of the
Jim Berkland G" system: 1) "the gravity gradient, or the forces exacted on the Earth by the gravitational pull of the Sun and the Moon." 2) "Gone Gatos" (missing cats) as indicated by advertisements in several newspapers. 3) "Geyser Gaps", seen as irregularities in the behavior of a geyser in the Napa Valley. Berkland's method has been said to also involve "a hodge-podge of factors". McClellan provides the most detailed description. Berkland starts with two lunar syzygies each month where the Sun, Moon, and Earth are aligned (corresponding to the new Moon and full Moon). He then sets a "seismic window" eight