Chapter : Geographic Setting and Impacts to the Environment Geological time with major evolutionary events in the fossil record William L. Kruczynski and Pamela J. Fletcher MYAEonMYA Era Period Major events 00 65 Cenozoic 1.8 Quaternary: Tertiary: Human evolution 251 Mesozoic Mammals diversify Paleozoic 542 PHANEROZOIC 65 Cretaceous: Proterozoic: Extinction of dinosaurs, Life begins in sea First primates, First flowering plants 145 Jurassic: First birds, Mesozoic Dinosaurs diversify 199 Triassic: First mammals, First dinosaurs 251 Permian: Major extinction, Reptiles diversify 299 2500 Carboniferous: Archean: First reptiles, Oldest rocks, Trees, seed ferns PRECAMBRIAN Earth curst forms 359 Devonian: First amphibians, 4000 Fish diversity 416 PaleozoicSilurian: First vascular plants Cenozoic Hadean: 444 Earth forms Ordovician: Setting and Impacts to the Environment Geographic Major diversification of animal life 488 Cambrian: First fish, First chordates (animal with backbone) 4600 542 www.enchantedlearning.com and Britanica Encyclopedia from Adapted 7KHgeological time scale is a method of relating the timing and relationship between events that have occurred GXULQJWKHKLVWRU\RI WKH(DUWK7KH(DUWKLVPRUHWKDQELOOLRQ\HDUVROGDQGDQDSSUHFLDWLRQRI WKHH[SDQVH RI JHRORJLFDOWLPHLVGLIÀFXOWWRYLVXDOL]H7KLVFKDUWVKRZVWKHVHTXHQFHRIPDMRUHYROXWLRQDU\HYHQWVWKDWDSSHDU in the geologic record. Geologists and earth scientists have used the relationship between layers and types of rocks, presence of plant and animal fossils, and radioactive dating to assemble a sequence of historical events that have occurred over geologic time. Geologic time is divided into four large segments called Eons: Hadean, Archean, 3URWHUR]RLFDQG3KDQHUR]RLF 7KH3KDQHUR]RLF(RQLVGLYLGHGLQWR(UDV3DOHR]RLF0HVR]RLFDQG&HQR]RLF7KHGLYLVLRQVDPRQJ(UDVUHÁHFW PDMRUFKDQJHVLQWKHIRVVLOUHFRUGLQFOXGLQJWKHH[WLQFWLRQDQGDSSHDUDQFHRI QHZOLIHIRUPV(UDVDUHGLYLGHGLQWR Periods, a unit of geologic time in which a single type of rock system is formed. Some Periods are divided into Epochs that are not shown on this chart, but a discussion of Epochs appears on subsequent pages in this chapter WKDWVXPPDUL]HWKHFUHDWLRQRIWKH)ORULGDSHQLQVXODWKHJHRORJ\RI VRXWK)ORULGDDQGWKHFlorida Keys, and the appearance and disappearance of shorelines and coral reefs. 'DWHVIURPWKH,QWHUQDWLRQDO&RPPLVVLRQRQ6WUDWLJUDSK\0<$ 0LOOLRQ\HDUVDJR .