ENV 151 Study Guide - Quiz Guide: Unconformity, Black Carbon, Gastrolith
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1. How did each philosophy view the age of the Earth?
The philosophy of catastrophism viewed the Earth as being about 5000 or so years old,
while uniformitarianism recognizes the Earth as being much older.
2. Distinguish between numerical dates and relative dates.
Numerical dates give us known ages of rocks and rock layers. Relative dates establish,
based on the order of rock layers, which rocks are older or younger than others.
3. What is the significance of an unconformity?
These breaks in the rock record represent times of significant geologic events. They can
help us identify intervals of time not represented in the rock record.
4. Distinguish among angular unconformity, disconformity, and nonconformity.
An angular unconformity is an area in which rocks have been tilted and uplifted, then
had horizontal deposition begin anew atop these tilted layers. A disconformity is a
region where erosion rather than deposition occurred, as between two sedimentary
layers widely separated in age. A nonconformity is a boundary between igneous or
metamorphic rocks and sedimentary strata.
5. Describe several ways that an animal or a plant can be preserved as a fossil.
If a vertebrate animal dies and is buried quickly, its bones may be preserved as fossils.
Sometimes animals are buried in sediment and dissolved by underground water, leaving
behind a fossil mold. Plants are sometimes fossilized by way of carbonization when
sediments and pressure squeeze out liquid and gaseous components of the plant and
leave a black carbon residue behind. Some small organisms may get trapped in tree sap
that turns into amber.
6. List three examples of trace fossils.
Burrows, tracks, coprolites, gastroliths.
7. What conditions favor the preservation of an organism as a fossil?
Rapid burial and possession of hard parts.
8. What is the goal of correlation?
Correlation can help geologists identify and match widely separated strata.
9. State the principle of fossil succession in your own words.
Older fossils will be deposited in rock strata that are in lower layers than younger