The global water cycle and continental erosion during Phanerozoic time (570 my)

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Abstract
Asensitivity study is conducted to determine what effect two mechanisms, namely continental size and latitudinal location might have on the global wtaer cycle. The global water cycle over Phanerozoic time (570 my) is established first by analyzing the distribution of rainfall (P), evaporation (E), and runoff (D), by bands of 10° of latitude, on the Present-day Earth and then applying these values to the ancient Phanerozoic world. In this backward projection, the global cosmic, climatic, and orographic conditions prevailing today, are supposed constant through time, while the only variable parameter controlling the system are the latitudinal positions of the continents and the relative area of continents and oceans.\ud The calculated Phanerozoic global runoff clearly shows that the humid periods are the Cretaceous (100 my), the Devonian-Silurian (400 my), and the Cambrian (500 my), while the dry periods are close to the Present-day (0 my), and the Permo-Triassic (200 my). The continal global runoff together with the survival rate of the volcanics are used to predict the fluctuations of the isotopic ratio 87Sr/86Sr in marine sediments. Predicted and measured values appear to be in good agreement (except for the Present) which somewhat validate the calculations. The continental runoff is also related to the sedimentation rate and used to estimate the specific erosion rate of the continents through the Phanerozoic. Thus the sedimemtation rate variations are understood as a consequence of the continental runoff fluctuations through time

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