Geological Time Scale PDF

Geological time scale It is an organised timeline of the history of the Earth. It shows major events in the Earth’s history and is divided...

Geological time scale It is an organised timeline of the history of the Earth. It shows major events in the Earth’s history and is divided into time units. Uses the age of rocks, fossils and events that formed them. Rock records and layers change revealing conditions over time. The geological time scale is divided into Eons, Eras, Periods and Epochs. Follows stratigraphy. Geog 4 Regional Geomorphology 6 Understanding the geological time scale The Precambrian extends from about 4.6 billion years ago to 541 million years ago little is known about this period since very few fossils or unaltered rocks have survived life first appeared on the planet some 3.9 billion years ago in the form of single-celled organisms. The Paleozoic extends from 541 to 252 million years ago fossil evidence shows that during this period, life evolved in the oceans and gradually colonized the land. Geog 4 Regional Geomorphology 7 Understanding the geological time scale cont.. The Mesozoic from 252 to 66 million years ago, It is also called the “age of reptiles” since dinosaurs and other reptiles dominated both marine and terrestrial ecosystems. It is also noteworthy that during this time the last of the Earth’s major supercontinents, Pangaea, formed and later broke up, producing the Earth’s current geography. The Cenozoic extends from the extinction of the dinosaurs, nearly 66 million years ago, to the present. Humans came into the picture until the last 2 million years. Geog 4 Regional Geomorphology 8 Geog 4 Regional Geomorphology 9 [Waugh, p.8] Geog 4 Regional Geomorphology 11