How do we measure the Earths Age? Geological Timescale How do we measure the Earths Age?

Geological Time Scale Shows an outline of how the Earths Development.

Geological Column: ordered arrangement of layers, based on relative ages of rock and in which the oldest is on the bottom layers. Represents the Earths history Distinguished by different layers Fossils in upper layers are newer than the ones toward the bottom Older rock and fossils are on the bottom of the column. This is being used by scientist, when radioactive dating can not be measured.

Division of Geological Time Used to mark major changed in time Indicators” climate, types of organisms found The Precambrian craton is exposed in the Grand Canyon where the Colorado River has cut through the younger sedimentary rocks.

How is it divided? Eons Eras Periods Epochs Eons: largest unit of geological timescale Eras: two or more periods Periods: longer than a epochs, shorter than an era Epochs: longer than age but shorter than a period

Precambrian Time The interval of time, in geologic time scale from Earths formation to the beginning of the Paleozoic Era, from 4. 6 Billion year to 542 million years. Life forms lack bones, shells or any hard parts commonly to form fossils. Stromatolites Stromatolites, reeflike deposits formed by blue green algae.

Paleozoic Era The geological era that followed the Precambrian time and that lasted from 543 million to 251 million years ago Supercontinent Pangaea was formed, tectonic activity created new mountain ranges Abundant fossil record, plants and animal species on Earth Scientist divided into seven periods

Paleozoic Era, and seven periods Cambrian Period (488 Million) Ordovician Period ( 444Million) Silurian Period (416 Million) Devonian Period (359 Million) Carboniferous Period (2 smaller periods){318Million-299Million} Permian Period (251 Million)

Mesozoic Era Geological ear that lasted from 251 million to 65.5 million years ago; also known the Age of the Reptiles Pangea broke into smaller continents Lizards, turtles, crocodiles, snakes and a variety of dinosaurs Rich in fossil record Split into 3 periods

Mesozoic Era and 3 periods Triassic Period (200 Million)-Pangea begins to break apart/first mammals appear (dinosaurs appeared) Jurassic Period (146 Million)- 1st primitive birds appear Cretaceous Period (65.6 Million)-first flowering plants, modern birds, the last of the dinosaurs become extinct (catastrophic meteorite impact)

Examples

Cenozoic Era-Present Period Current geologic ear, which began 65.5 million years ago, also called the Age of Mammals Split into 2 periods and 7 epoch

Tertiary Period 65.5 Million – 1.8 Million Paleocene Epoch Eocene Epoch – most modern mammal families, including whales, carnivores, hoofed animls, and primates have appeared. And first grasses Oligocene epoch- india collides with Asia, and Antarctica drifts over the south pole Miocene Epoch ( 5.3 million) Pliocene Epoch- first early humans, Modern Ice Age begins

Quaternary Period Pleistocene Epoch- ice sheets advanced and retreated several times, animals adapted to climate. Species, sloths, dire wolves became extinct. Fossil record indicated early humans discovered during this times. Also, known as Stone Age. Holocene Epoch –Present (modern humans) began 11,500 years ago, the last glacial period ended. Sea level rose, modern humans( Homo Sapiens).

Summary Geological time is broken up into eons, eras, periods. Epochs, and ages Rock record reveals the evolution of marine invertebrates and vertebrates during Paleozoic Era Mesozoic Era ended with mass extinction of dinosaurs Rock record of the Cenozoic Era includes the present period and reveals rise of mammals as dominant life forms.

Interactive Notebook Go to the following link and complete the concept map and copy in your notebook once completed. http://my.hrw.com/sh/hq6f_0030363667/student/ch09/hq6f09_m.ht m