EARTH’S HISTORY AND GEOLOGICAL TIME SCALE WHAT IS THE EARTH’S TIME SCALE? Geological time scale - a record of the life forms and geological events in Earth’s history. Scientists developed the time scale by studying rock layers and fossils worldwide. Relative dating – determines the rocks and events in their chronological order without knowing their actual age. Absolute dating – actual ages of rocks and events Radioactive dating helped determine the absolute divisions in the time scale. THE AGE OF THE EARTH 4,600,000,000/ 4.6 Billion years old/4600 Mya The earth’s 4.6 billion year history is divided into major units of time: 1. Precambrian Eon 2. Phanerozoic Eon Paleozoic Era Mesozoic Era Cenozoic Era One Super Eon and Four Eras PRE-CAMBRIAN Super Eon – 88% of earth’s history Paleozoic (ancient life) - 544 M years ago…lasted 300 million yrs Mesozoic (middle life) - 245 M years ago…lasted 180 million yrs Cenozoic (recent life) - 65 M years ago…continues through present day NOTE: Today we are in the Holocene Epoch of the Quaternary Period of the Cenozoic Era . PRECAMBRIAN EON Hadean Era Chaotic eon 4.6- 3.8 billion years/ Gya Lasted for 800 Mya Hades – Hell Accretion of Earth, Theia Event, Formation of Moon, Heavy bombardment, Volcanism, Oceans and atmosphere formed differentiation of core, mantle and protocrust. Archean Era 3.8-2.5 billion years/ Gya Lasted for 1.3 Gya Oldest fossil - Stromatolites Atmosphere – contain METHANE Earth was covered with ocean Formation of relatively stable crust Continent formation Proterozoic Era 2.5-542 Mya Lasted for 1.9 Gya Longest Era/ half of the age of the Earth - 42% of the Earth’s History Oxygenation of the Atmosphere “Early life” - Photosynthesis Origin and diversification of eukaryote life Appearance of multicellular animal life
You've reached the end of your free preview.
Want to read all 3 pages?
- Spring '18
- Extinction event, Carboniferous, Cretaceous–Tertiary extinction event, Geological history of Earth