The Calymmian (from Greek calymma, "cover") is the first geologic period in the Mesoproterozoic Era and lasted from 1600 million years ago to 1400 million years ago. Instead of being based on stratigraphy, these dates are defined chronometrically. Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. ... In geology, a period or age is a time span of many millions of years that are assumed to have had similar characteristics. ... The Mesoproterozoic era is a geologic period that occurred between 1600 and 900 million years ago. ... ERA is an abbreviation for several different things, including: the Equal Rights Amendment, a proposed, but unratified, Constitutional amendment in United States Earned run average, a baseball statistic Engine Room Artificer Education Reform Act Engineering Research Associates, a pioneering computer firm from the 1950s Academy of European Law Trier Explosive... Stratigraphy, a branch of geology, is basically the study of rock layers and layering (stratification). ...

The period is characterised by expansion of existing platform covers, or by new platforms on recently cratonized basements. The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the one we live in by relatively shallow seas and gulfs. ... A craton is an old and stable part of the continental crust that has survived the merging and splitting of continents and supercontinents for at least 500 million years. ...

The supercontinent Columbia broke up during the Early Calymmian some 1500 million years ago. A supercontinent is a mass of land comprising more than one continental core, or craton. ...

External link

• GeoWhen Database