Geologic Time Scale PDF

GEOLOGIC TIME SCALE GEOLOGIC TIME SCALE  tabular presentation of the history of life based on geologists’ study of rocks and the fossils they contain  all the pieces of information about Earth are arranged chronologically from the oldest (bottom table) to the most recent ( top table) t...

GEOLOGIC TIME SCALE GEOLOGIC TIME SCALE  tabular presentation of the history of life based on geologists’ study of rocks and the fossils they contain  all the pieces of information about Earth are arranged chronologically from the oldest (bottom table) to the most recent ( top table) the “calendar” for events in Earth history subdivides all time into named units of abstract time called—in descending order of duration—eons, eras, periods, epochs, and ages  One way to distinguish and define each segment of time is by the occurrence of major geologic events the appearance (and disappearance) of significant life-forms starting with the formation of Earth’s crust followed by the appearance of ever-changing forms of life on Earth EON broadest category of geological time Earth's history is characterized by four eons from oldest to youngest Hadeon, Archean, Proterozoic, and Phanerozoic ERA very long span of geologic time second longest portions of geological time (eons are the longest) One Era is hundreds of millions of years in duration. ERA The Phanerozoic Eon is divided into three eras Paleozoic Mesozoic Cenozoic eras. named for the kinds of fossils that were present Cenozoic is the youngest era and the name means “new life”. PERIOD basic unit of geologic time lasts tens of millions of years which is the time it takes to form one type of rock system EPOCH lasts several million years unit of geological time during which a rock series is deposited subdivision of a geological period word is capitalized when employed in a formal sense (e.g., Pleistocene Epoch) Additional distinctions can be made by appending relative time terms, such as early, middle, and late. AGES referred to as "stages" only a few million years in length present age is the Meghalayan