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Earth History Textbook Assignment: Pgs 588-609
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Reading Checks:
o Pg592: Scientists need a geologic time scale it enables them to find
relationships among the geologic events, environmental conditions, and
fossilized life-forms that are preserved in the rock record.
o Pg598: 1. Disconformity: When a horizontal layer of sedimentary rock
overlies another horizontal layer of sedimentary rock, ; eroded surface.
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2. Nonconformity: When a layer of sedimentary rock overlies a
layer of igneous or metamorphic rock, i.e. granite or marble, the eroded
surface is easier to identify.
o Pg603: Radiometric dating is not useful for sedimentary rocks because the
minerals in most sedimentary rocks were formed from pre-existing rocks.
o Pg604: Tree Rings can show the past environmental conditions by
consisting of a pair of early season and late season growth rings.
o Pg607: Fossils with original preservation are rare because their
preservation requires extraordinary circumstances, such as freezing, arid,
or oxygen-free environments.
o Pg608: 1. Recrystalization: When a buried hard part is subjected to
changes in temperature and pressure over time.
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2.Mineral Replacement: The original mineral is replaced by a
mineral from water, whereas in recrystalization the original minerals
transformed into a new mineral.
Questions: Pgs 613-614
Geologic Time Scale
Unconformity
Radioactive decay
Precambrian
Correlation
Period: Are generally tens of millions of years in duration, though some periods
of the Precambrian are longer. Epoch: Are generally hundreds of thousands to
millions of years in duration.
7. Altered hard part: Fossil whose organic material has been removed and whose
hard parts have been changed by recryalization or mineral replacement.
Original preservation: Describes a fossil with soft and hard parts that have
undergone very little change since the organisms death.
8. Absolute-age dating: Method that enables scientists to determine that actual age
of certain rocks and other objects.
Relative-age dating: To determine how
many years ago an event occurred; gives scientists a clear understanding about
geologic events in earth’s histories.
9. Fossil: The remains or impression of a prehistoric organism preserved in a
petrified form or as a mold or cast in rock. Index fossil: Remains of plants or
animals that were abundant, widely distributed, and existed briefly that can be
used by geologists to correlate or date rock layers.
10. Mold: Fossil that can form when a shelled organism decays in a sedimentary
rock and is removed by erosion or weathering, leaving a hollowed-out impression.
Cast: Fossil formed when an earlier fossil of a plant or animal leaves a cavity that
becomes filled with minerals or sediment.
11. Principle of Inclusions
12. Uniformitarianism
13. Key Bed
14. Evolution
15. (1)
16. (4)
17. (1)
18. (4)
19. (3)
20. (1)
21. (2)
22. (4)
23. (4)
24. (2)