Its interesting you should mention land bridges...
"Movement of the Tropics and the Arctic and Antarctic circles
See also: Axial tilt.
By definition, the positions of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle all depend on the tilt of the Earth's axis relative to the plane of its orbit around the sun, known technically as the "obliquity of the ecliptic". As of 2000, the mean value of the tilt was about 23 degrees 26' 21". However, this angle is not constant, but has a complex motion determined by the superimposition of many different cycles with short to very long periods. As the axial tilt varies, so do the positions of the Tropics and the Arctic and Antarctic circles.
The main long-term cycle causes the axial tilt to fluctuate between about 22.1 degrees and 24.5 degrees with a 41,000 year periodicity. As a consequence of this cycle the average value of the tilt is currently decreasing by about 0.47" per year. This causes the Tropics of Cancer and Capricorn to drift towards the equator by about 15 metres per year, and the Arctic and Antarctic Circles to drift towards the poles by the same amount. As a result of the movement of the Tropics of Cancer and Capricorn, the area of the Tropics decreases worldwide by about 1100 square kilometres per year on average.
The Earth's axial tilt is subject to additional shorter-term variations due to nutation, of which the main term, with a period of 18.7 years, has an amplitude of 9' 21" (corresponding to almost 300 metres north and south). There are then still many smaller terms, resulting in varying daily shifts of some metres in any direction.
Finally, the Earth's rotational axis is not exactly fixed with respect to the Earth, but undergoes very small fluctuations, called polar motion, which have a small theoretical effect on the positions of the abovementioned parallels.
Short-term fluctuations over a matter of days do not directly affect the location of the extreme latitudes at which the sun may appear directly overhead, or at which 24-hour day or night is possible, except when they actually occur at the time of the solstices. Rather, they cause a theoretical shifting of the parallels, that would occur if the given axis tilt were maintained throughout the year."
Understanding the nature of "the ground we stand on" as well as the nature of water is enough to convince me that trust in the integrity of most so-called experts is misplaced. We cannot pick and choose what to believe from the accounts of our ancestors; they who were more in touch with nature than we'll ever be; they who understood cycles of destruction and regeneration and in most instances were not imprisoned by their mortal selves.
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