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ancient Rodinia supercontinent. These ancient continental assemblages and intervening seas agree in principle with conventional plate tectonic mblages, without the requirement for extensive ancient Panthallassa and Tethys oceans. The significance to global tectonics is that—without the extensive Panthallassa and Tethys oceans—climatic zonation, geography, distribution and migration routes of marine and terrestrial life- forms are dramatically simplified. Modelling studies indicate that the primordial Earth size for the Archaean aeon was approximately 1,700 kilometres in radius and remained relatively static throughout the Archaean to the Late Mesoproterozoic era, increasing by approximately 60 kilometres during 3,000 million years of Earth history. Since the Proterozoic aeon, there has been a steady to rapidly accelerating expansion to the present. The present rate of radial Earth expansion is calculat- ed to be 22 millimetres per year, which equates to a 140 mm/year increase in circumference. sedimentary rocks dating back to over 3,000 million years ago, and fossilised life-forms dating back to the beginning of the Cambrian period, about 560 million years ago, abound in our museums of natural history. On an expanding Earth, the ocean water and atmosphere were added at the same time and rate as the sea-floor crust and underly- ing mantle were added. Modern investigations along active rift zones demonstrate that these, as well as volcanoes, are major sources of new water and gases. The sea-floor crust, ocean water and atmosphere all originate from deep within the Earth's mantle and have been added to the surface crust at an accelerating rate throughout geological time. This increase in new ocean water and atmosphere is considered to have resulted by a process of mantle outgassing, as a natural response to a decrease in mantle tempera- ture and pressure conditions with time. Ss leelliiedeinelaanenl ERE Sell eee neni: Sanenenelenee increase in circumference. 2 What about subduction? On a constant-radius Earth, sea-floor crust generated along each = What about the ocean water and atmosphere? of the mid-ocean ridges must be disposed of somewhere. Early Researchers have argued that before the Triassic period an researchers considered that crust was being subducted around the ancient Earth with a continuous continental crust would be margins of the Pacific Ocean, and the apparent overriding of the covered by an ocean with an average depth of 6.3 kilometres. If | North Pacific Ocean plate by North America and Australia is this were the case, then terrestrial life-forms would not have often quoted as a classic example of plate consumption by sub- evolved and continents would have only been exposed to erosion duction. Here, up to 5,000 to 15,000 kilometres of North Pacific fairly recently in Earth history. However, all continents contain Ocean sea-floor crust has supposedly been subducted beneath the North American conti- ___ Constant Earth Radius nent, and the surface area of the Pacific Ocean has Bodo supposedly decreased as the Indian, Atlantic and Emyed (1260 Southern oceans have opened. Expanding Earth Models The history of the ee perenanties 5000 eras has then supposedly O) Emeites! Continental Lithosphere been one of east-west and north-south contraction o} ancient Panthallassa an Carey (1968 Tethys oceans to the size Hilgenberg (1382) 4000 = of the modern Pacific i Ocean, subduction of al G pre-Mesozoic sea-floor E crust, and subduction of a = substantial quantity of 4000 « sea-floor crust generate = during the Mesozoic an Mowar [1900 *) = Cenozoic eras. Vogel (1580 2 Ft Since the introduction 4 a z of the plate tectonic o hypothesis, magnetic Empirical Primordial Earth : 2nd mapping of the oceans = Radtuse Tod km en =" has revealed that, as well ; ¥ P | as sea-floor spreading in | | | i lal , the Indian, Atlantic, i A ] 5 I é- 1 i Southern and Arctic id | [i LI z H : i000 oceans, the Pacific Ocean 2500 2000 1500 1000 500 is also undergoing exten- sive sea-floor spreading, Time (Million Years) right where subduction around the margins is Figure 4. Exponential Earth expansion from the Archaean to the present. Graph shows post-Triassic expansion derived supposedly taking place from oceanic mapping and pre-Jurassic expansion derived from an Archaean primordial Earth radius of approximately (see figure 1). Plate 1,700 kilometres. Spherical expanding Earth models constructed are shown as filled squares and circles on the graph. motion measurements = What about the ocean water and atmosphere? Researchers have argued that before the Triassic period an ancient Earth with a continuous continental crust would be covered by an ocean with an average depth of 6.3 kilometres. If this were the case, then terrestrial life-forms would not have evolved and continents would have only been exposed to erosion fairly recently in Earth history. However, all continents contain 44 - NEXUS Expanding Earth Models oO Empirical Oceanic Uthosphere Magtow (1996) 0 Eepitcal Continental Lthoopnere Time (Million Years) OCTOBER — NOVEMBER 2000