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imperceptibly, and their movements have been measured by satellite photos and other means. North America is moving away from Europe at the rate of an inch per year. New instruments are able to measure the magnetic fields of rocks on the ocean's bottom. These measurements indicate that the Earth's magnetic field has frequently shifted, the North Pole be- coming the South Pole and vice versa. Such magnetic shifts have occurred at least 171 times in the past seventy-sfac mil Bon years -further proof that the Earth's crust is wriggling about.* What all this means is that, about two hundred million years ago during the age of the great reptiles - the Paleozoic age - this was an entirely different planet. Perhaps it harboured life forms now unimaginable to us. Then it broke up, and new continents were formed, new climatic changes occurred, the physical environment itself may have changed. These changes could have brought about the sudden or gradual change of the life forms as they altered to adapt to the new conditions. Some of the puzzling erratics discussed in Chapter One could have been produced by a form of intelligent life now lost and forgotten. But a lot of other changes can occur in two hundred million years. It is doubtful if even the most advanced civilization could produce any quantity of monuments and artifacts which could withstand millions of years of erosion and geological change. The Atlantophiles are not too happy with the continental drift theory because it virtually excludes the possibility that any large land mass could have existed between North America and Europe. It might not rule out Mu or Lemuria, however. Other stubborn cultists are already leaping on to the continental drift bandwagon and claiming one of those two land masses as their favoured lost continent. Our flimsy knowledge of the very ancient past is based entirely upon the discovery and interpretation of fossils found in the various lock layers of the Earth's crust. This inexact science called paleontology is only two hundred years old. We haven't dug deeply enough or studied things thoroughly enough to reach reliable conclusions about the distant past So many of the facts commonly accepted today are only educated guesses. If the Earth has suffered truly cataclysmic changes in the past two hundred million years, we must first know of and understand those changes completely before we can accurately assess the meanings of rock formations. It seems unlikely that we will ever be able to develop methods for collecting evidence that will give us conclusive truths about the Earth's past. Astronomers and mineralogists were astounded and upset by the rocks our astronauts scooped up ofi the surface of the moon, because they indicated that the moon was four billion years old or even older, and it may be even older than the Earth itself. Some astronomers had been pushing the theory that the moon was really just a chunk of the Earth that had been scooped out of the Pacific Ocean area and tossed into space somehow. That theory and many others went down the drain when our first space module dropped on to the Sea of Tranquillity. Geologists and paleontologists have developed reasonable evidence that the Earth has passed through several glacial periods, or ice ages. These seem to be cyclic, with minor ice ages “ See "Reversals of the Earth's Magnetic Field’. Allan px. Scientific American, February 1967.