Chapter : Geographic Setting and Impacts to the Environment

Geological with major evolutionary events in the record William L. Kruczynski and Pamela J. Fletcher

MYAEonMYA Major events 00 65 1.8 : : 251 diversify 542 65 : : Extinction of , begins in sea First , First flowering 145 : First , Mesozoic Dinosaurs diversify 199 : First mammals, First dinosaurs 251 : Major extinction, diversify 299 2500 : : First reptiles, Oldest rocks, Trees, curst forms 359 : First , 4000 Fish diversity 416 PaleozoicSilurian: First vascular plants Cenozoic : 444

Earth forms : Setting and Impacts to the Environment Geographic Major diversification of life 488 : First fish, First (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 . and earth scientists have used the relationship between layers and types of rocks, presence of and animal , 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 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 reefs. 'DWHVIURPWKH,QWHUQDWLRQDO&RPPLVVLRQRQ6WUDWLJUDSK\0<$ 0LOOLRQ\HDUVDJR