** The Ediacaran is the only formal system in the Proterozoic with a global boundary stratotype section and point (GSSP). A geologic time scale is composed of standard stratigraphic divisions based on rock sequences and is calibrated in years (Harland and others, 1982). Geological Survey Geologic Names Committee, 2007, Divisions of geologic time-major chronostratigraphic and geochronologic units: U. Over the years, the development of new dating methods and the refinement of previous methods have stimulated revisions to geologic time scales. Clouds formed and storms raged, raining more and more water down on the primitive earth, cooling the surface further until it was flooded with water, forming the seas.It is theorized that the true age of the earth is about methods to determine the age of rocks means scientists have to rely on when the rock was initially formed (as in - when its internal minerals first cooled).As the collisions tapered off the earth began to cool, forming a thin crust on its surface.
The heat had been generated by the repeated high speed collisions of much smaller bodies of space rocks that continually clumped together as they collided to form this planet.This aspect of Werner's model was useful for explaining the origin of tilted sedimentary rocks.(dark brown) Flat lying sedimentary rocks were eventually precipitated.The secondary rocks were thought to include interlayered basalts, which Werner thought formed by combustion of buried coal layers.The Scottish geologist James Hutton (1726-1797) argued that granite and basalt by solidification within the earth (as opposed to precipitating in from oceanwater).(light brown) Next, fossil-rich sedimentary rocks were precipitated.These rocks are tilted due to deposition on the non-horizontal surfaces of primitive rocks.Since publication of a chart showing divisions of geologic time in the seventh edition of the USGS guide Suggestions to Authors (Hansen, 1991), no other time scale has been officially endorsed by the USGS. M., 2008, The concise geologic time scale: Cambridge, U. For consistent usage of time terms, the USGS Geologic Names Committee (GNC; see box for members) and the Association of American State Geologists (AASG) developed Divisions of Geologic Time (fig. (Also available at Ogg, Gabi, comp., 2009, Global boundary stratotype sections and points (GSSP): International Commission on Stratigraphy, accessed May 10, 2010, at Due to the forces of , our planet is also a very dynamic one; new mountains forming, old ones wearing down, volcanoes melting and reshaping new crust. Scientists are still trying to unravel one of the greatest mysteries of earth: When did "life" first appear and how did it happen?The continual changing and reshaping of the earth's surface that involves the melting down and reconstructing of old rock has pretty much eliminated most of the original rocks that came with earth when it was newly formed. It is estimated that That's pretty much all there was for about the next two billion years.