Geologic Time

Geologic time scale -Precambrian (>540 my), Paleozoic (>248 my), Mesozoic (>65 my), Cenozoic; mostly algae and bacteria during Precambrian fossils become common at end of Precambrian, invertebrate sea shells, and corals common in Paleozoic, also some fish and amphibians, supercontinent of Pangaea, extinction marks end of Paleozoic, reptiles and dinosaurs dominate Mesozoic, extinction at end of Mesozoic, warm furry mammals dominate the Cenozoic, lions, tigers, bears, squirrels

Relative dating: layer sequence, superposition, original horizontality, lateral continuity, cross-cutting relationships, unconformities,

fossils: principle of fossil succession, age range, fossil assemblage

Absolute dating - radiometric dating: radioactive decay - the spontaneous transformation of an unstable parent isotope into a stable daughter at a constant rate; half-life - time it takes for 1/2 the unstable parent to transform into stable daughter;

Explain the difference between relative and absolute dating. Describe the ways by which relative ages are determined. How is absolute age determined?

What is the principle of fossil succession and how is it used to determine the age of a rock? Explain how age ranges and fossil assemblages are used in this process.

List (in order) the four main geologic time periods. What types of organisms were common during each period? What global event happened to cause the end of each time period?

Be able to determine the sequence of events from a block diagram.

Carefully define the terms: radioactive decay and half-life. How are these used to date rocks?

Be able to determine the age of a rock given the amount of parent, the amount of daughter, and the length of the half life.

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