Nature of Fossils Fossil –Trace of long dead organism Where Found –Sedimentary rock How Created –Dust, sand, mud deposited by wind/water over dead organisms Develop From –Shell, bone, teeth, stem
Types of Fossils Mold –Imprint on rock such as limestone –Shape of organism Cast –Mold filled with hard minerals Amber –Fossilized tree sap
Robert Hooke In 1668 –Concluded fossils are remains of once living plants and animals –What else did he do? Remember way back when… –Hmmm?
Distribution of Fossils Age –Relative Steno 1670 Law of Superposition Determined by fossils position in strata/rock Oldest fossils = deepest youngest = surface –Absolute Radioactive dating Radioactive isotopes –Carbon-14; Carbon-12 –Ratio of decay of carbon-14 to stable carbon-12
Succession of Forms Extinct –Species no longer exists Mass Extinction –Period in which large number of species disappear Biogeography –Study of geographical distribution of fossils & living organisms –Ex of biogeographyEx of biogeography
Geological History of Earth Table 15-1 Era Period Epoch Interactive geologic time