Geologic Time Scale PDF

GEOLOGIC DIVISION  GEOLOGIC TIME SCALE A complex and fascinating system for understanding Earth’s history and the evolution of life. Based on the physical and biological evidence preserved in the rock record, which has been accumulated over centuries of geological research ...

GEOLOGIC DIVISION  GEOLOGIC TIME SCALE A complex and fascinating system for understanding Earth’s history and the evolution of life. Based on the physical and biological evidence preserved in the rock record, which has been accumulated over centuries of geological research  GEOLOGIC TIME SCALE Eons - largest units of geologic time, spanning hundreds of millions to billions of years, and each represents a significant phase in Earth’s history.  GEOLOGIC TIME SCALE Eras - subdivision of eons, and they span tens to hundreds of millions of years; defined by major changes in the Earth’s climate, geography, and diversity of life.  GEOLOGIC TIME SCALE Periods - major subdivisions of geologic time. Geologic periods are subdivision of eras; defined based on major changes in the fossil record, which reflect changes in the Earth’s environment and the evolution of life;  GEOLOGIC TIME SCALE Epoch - subdivision of geologic periods. They are also defined by changes in the Earth’s rock record, but these changes are generally less significant than those that define periods; generally hundreds of thousands to millions of years  PRE-CAMBRIAN Hadean Archean Proterozoic era  PRE-CAMBRIAN Started more than 500 million years ago Covers approximately 88% of Earth’s history. Started with the planet’s creation about 4.5 billion years ago from dust and gas orbiting the Sun and ended with the emergence of complex, multi- celled organisms almost four billion years later.  PRE-CAMBRIAN Ediacaran Period – marks the first appearance of a group of large fossils collectively known as the “Ediacara Biota” Cryogenian Period – when complex animal life got going.; emerged the evolutionary group that would give rise to jellyfish and corals, mollusks, snails, fish, dinosaurs. Proterozoic era- modern plate tectonics became active, and the ancient cores of the continents moved over wide areas of the globe.  PALEOZOIC ERA “Old Life” Started more than 540 millions of years ago and lasted for more than 300 million years Began with the breakup of the supercontinent Rodinia into continents Gondwana and Laurentia  PALEOZOIC ERA Cambrian Ordovician Silurian Devonian Carboniferous Permian  CAMBRIAN PERIOD Marks an important point in the history of life on Earth; It is the time when most of the major groups of animals first appear in the fossil records Sometimes called as “Cambrian Explosion”, because of the relatively short time over which diversity of forms appears.  ORDOVICIAN PERIOD Lasted almost 45 million years, beginning 488.3 million years ago and ending 443. 7 million years ago. The Ordovician is best known for its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts.  SILURIAN PERIOD A time when the Earth underwent considerable changes that had important repercussions for the environment and life within it. One result of these changes was the melting of large glacial formations which contributed to a substantial rise in the levels of the major seas.  SILURIAN PERIOD The Silurian witnessed a relative stabilization of the Earth’s general climate, ending the previous pattern of erratic climatic fluctuations. Coral reefs made their first appearance during this time, and the Silurian was also a remarkable time in the evolution of fishes. It is also at this time that our first good evidence of life on land is preserved, such as relatives of spiders and centipedes, and also the earliest fossils of vascular plants  DEVONIAN PERIOD The vegetation of the early Devonian consisted primarily of small plants, the tallest being only a meter tall. By the end of the Devonian, ferns, horsetails and seed plants had also appeared, producing the first trees and the first forests. During the Devonian, two major animal groups colonized the land (tetrapods and arachnids)  CARBONIFEROUS PERIOD The term “Carboniferous” comes from the England, in reference to the rich deposits of coal that occur there. Its duration is approximately 60 million years makes it longest period of the Paleozoic era Terrestrial animal life was well established by the carboniferous period. Also called as the Age of Amphibians, during which amphibians became dominant land vertebrates and diversified into many forms including lizard-like, snake –like and crocodile like.  PERMIAN PERIOD During the Permian period, earth’s crustal plates formed a single, massive continent called Pangaea On land, reptiles replaced amphibians in abundance. The last period of the Paleozoic era. It ended with the greatest mass extinction in the last 600 million years. Up to 90% of marine species disappeared from the fossil record, with many families, orders, and even classes becoming extinct.  MESOZOIC ERA The ancestors of major plant and animal groups that exist today first appeared during the Mesozoic, but this era is best known as the time of the dinosaurs Divided into three groups: Triassic, Jurassic, and Cretaceous Period In this era, the most significant land mass activity was the gradual rifting of the supercontinent Pangaea.  TRIASSIC PERIOD The rise of the dinosaurs According to Dr. Mike Day, “The Triassic is an interesting period. It forms the transition between the late Paleozoic era, which was mainly populated by mammal-like reptiles, and the Mesozoic era, when the archosauria reptiles (a larger group of reptiles that first appeared about 251 million years ago), which includes the dinosaurs.  JURASSIC PERIOD Characterized by a warm, wet climate that gave rise to lush vegetation and abundant life. It is a time of significant global change in continental configurations, oceanographic patterns, and biological system. During this period the supercontinent Pangaea split apart. May new dinosaurs emerged- in great numbers.  CRETACEOUS PERIOD It was the longest period of the Mesozoic era which lasted for 79 million years. The Cretaceous began 145.0 million years ago and ended 66 million year ago It followed the Jurassic Period and was succeeded by the Paleogene Period. This time, we find the first fossils of many insect groups, modern mammal and bird groups, and the first flowering plants  CENOZOIC ERA It spans only about 65 million years, from the end of the Cretaceous Period and the extinction of non-avian dinosaurs to the present Age of mammals because the largest land animals have been mammals during that time Mass extinctions create opportunities for new life to thrive, and mammals filled the gap that dinosaurs left behind.  PALEOGENE During the Paleogene, the continents drifted farther apart, heading toward their modern positions Lasting 43 million years, the Paleogene is most notable for being the time in which mammals evolved from relatively small, simple forms into a large group of diverse animals in the wake of Cretaceous – Paleogene extinction event that ended the preceding Cretaceous Period.  NEOGENE A time of big changes for the Earth. The climate became cooler and drier Grasslands replace forest The animals had to adapt to these changing conditions or face extinction  QUATERNARY The Quaternary Period is the third and last of the three periods of the Cenozoic Era. You and I are living in this period, which began only 2.58 million years ago. The age of humans.