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Time- a limited period or interval, as between two successive events. Seconds Minutes Hours Days Years 1. 1. Relative Time- subdivisions of the Earth's geology in a specific order based upon relative age relationships. These subdivisions are given names, most of which can be recognized globally, usually on the basis of fossils. Example: Thanksgiving is between Halloween and New Year’s Eve. Fossil- remains, impressions, or other evidence of life preserved in rock. 1. 2. Absolute Time- numerical ages in "millions of years" or some other measurement. These are most commonly obtained via radiometric dating. Example: The school year is 180 days long. mya = millions of years ago bya = billions of years ago Example: The following are equal amounts of time 3,800,000,000 years ago 3,800 mya 3.8 bya The Earth is thought to be 4.6 billion years old. Can you grasp how big 1 billion is??? Hmmm……. Lets put it in perspective! Geologic Time Scale Subdivided into segments of time: Largest Eon Era Period Smallest Epoch Geologic Time Scale Subdivided into segments of time: Youngest Oldest 3-Eons Phanerozoic Proterozoic Archean Geologic Time Scale Subdivided into segments of time: Youngest Eon Era Phanerozoic Cenozoic Mesozoic Paleozoic Divided into 3 Eras Oldest Geologic Time Scale Subdivided into segments of time: Period Eon Phanerozoic Era Cenozoic Youngest Quaternary Tertiary Cretaceous Neogene Paleogene Jurassic Triassic Mesozoic Permian Carboniferous Devonian Paleozoic Oldest Silurian Ordovician Cambrian Pennsylvanian Mississippian Geologic Time Scale Subdivided into segments of time: Period Eon Phanerozoic Era Cenozoic Youngest Mesozoic Paleozoic Quaternary Holocene Tertiary Pleistocene Cretaceous Pliocene Jurassic Miocene Triassic Oligocene Permian Eocene Carboniferous Paleocene Devonian Silurian Oldest Epoch Ordovician Cambrian Geologic Time Scalesummary of major events in Earth’s past that are preserved in the rock record. Based on relative and absolute time. Found on pages 8-9 in your ESRT Hadean Eon Accretion disc Meteorite Hadean Eon 4.5 to 3.8 billion years ago •Pre-dates the Earth •No rocks on Earth are this old, except for meteorites •Solar system formation •Earth turned from molten to solid about 3.8 bya •Earth began forming “protocontinents” in the Achean Eon 430 Million Years Ago! New York Diatoms Trilobites 540-250 million years ago Eurypterids Horseshoe Crabs Eurypterids Stomatolites Cycads Today Cycad Fossils Dinosaurs 1. Eon- the largest segment of geologic time. Oldest Archean: Greek for “ancient” Proterozoic: Greek for “earlier life” Youngest Phanerozoic: Greek for “visible life.” We are currently in the Phanerozoic Eon. 2. Era- Eons are subdivided into Eras based on the fossil record. Oldest Paleozoic: “old life” Mesozoic: “middle life” Youngest Cenozoic: “recent life.” We are currently in the Cenozoic Era. 3. Period- Eras are subdivided into periods. Names of time periods are based on the names of rock formations around the world. We are currently in the Quaternary Period. Examples: Permian period comes from the province of Perm in Russia Pennsylvanian period comes from the US state. Cretaceous period is Latin for “chalk.” 4. Epoch- smallest unit of time on the geologic time scale. We are currently in the Holocene Epoch.