If the Earth Stood Still Continued from page 67 dynamic. The net result of these dynamic adjustments is that the earth is slowly becoming more and more like a sphere. However, it will take billions of years before the earth stops spinning, and the gravitational equipotential creates a mean sea level that is a perfect sphere. About the Author Witold Fraczek is a longtime Esri employee who currently works in the Application Prototype Lab. eons, it showed that the length of a day was several hours shorter than today. Consequently, during the Devonian period (400 million years ago), the earth rotated about 40 more times during one revolution around the sun than it does now. Because the continents have drifted significantly since that time, it is difficult to make estimates of the land versus ocean outlines for that era. However, we can be certain that—with a faster spinning speed in the past—the equatorial bulge of oceanic water was much larger then than it is today. Similarly, the ellipsoidal flattening of the earth was also more significant. The influence of the rate of the earth’s rotation has a dominant effect on the geometry of the globe, in terms of the globe’s overall shape as well as the outline of the global ocean. The earth’s physical relief is only a secondary factor controlling the delineation of oceans. The slowdown of earth’s rotation will continue for 4 billion years—as long as we can imagine. The slowdown infinitesimally—but steadily— changes the globe’s geometry and makes it Large land areas near the equator continue growing and join with each other. By now, nearly all of Canada, Europe, and Russia are covered by a northern circumpolar ocean. As the last water connection between the two large neo-oceans is broken, an equatorial megacontinent is formed. Ocean areas in proximity to the continent are becoming more shallow while the waters of the polar areas are getting deeper and deeper. Former abyssal plains and oceanic trenches become inland seas within the new continent. 68 ArcUser Summer 2010 www.esri.com