Geologic Time
The longest period of geologic time is called a(n)....
Eon
This is the amount of time it takes for 50% of a radioactive sample to decay
Half-life
Relative dating helps us order rock layers without knowing their specific ______________.
Age
Fossils are found in this type of rock
Sedimentary
True or false: a period is shorter than an epoch?
False
Which era came first: Cenozoic, Paleozoic, or Mesozoic?
Paleozoic
The starting material that we can use to measure age in a rock or fossil is called...?
a) Daughter isotope b) Parent isotope
c) Starting material d) Parent rock
b) Parent isotope
The Law of Superposition tells us that rock layers on top are ________________ than those underneath them.
younger
What kind of fossil could be described as a negative impression of a once-living thing in rock?
Mold
True or false: an example of a mold fossil is a footprint
False
(footprint = trace)
What period of time do we currently live in?
a) Quaternary b) Tertiary
c) Cretaceous d) Permian
a) Quaternary
True or false: the daughter isotope is always the same element as the parent isotope?
False
Which relative dating law tells us that rock layers are originally laid flat (and any tilt, fold, or fault must happen after they are formed)?
Law of Original Horizontality
What is an example of a true-form fossil?
Bone, tooth, an actual thing
True or false: there was an extinction at the end of the Ordovician time period?
True
Which period of geologic time could be described as the time of the first reptiles?
a) Ordovician b) Triassic
c) Silurian d) Carboniferous
d) Carboniferous
Ms. Craft starts with a sample of 5 g of C-14. How many half-lives have passed if she only has 0.625 g of C-14 left?
3 half-lives
5/2 = 2.5; 2.5/2 = 1.25; 1.25/2 = 0.625
A layer of rock or other material that overlaps with pre-existing layers is called a(n).....?
Intrusion
What is one way an organism could be turned into a fossil besides using sediment?
Ice, amber, or tar
Why can't fossils be found in igneous or metamorphic rocks?
Heat and pressure
Organic material burns before it is preserved
Which extinction involved an asteroid colliding with Earth?
a) End Ordovician b) End Permian
c) End Cretaceous d) Late Devonian
c) End Cretaceous
The half-life of C-14 is 5,730 years. How old would a fossil containing C-14 be after three half-lives have passed?
17,190 years old
This geologic feature is typically depicted as a thin line that cuts through layers of rock
Fault
If layers A and C contain fossils but layer B does not, what could have happened during the time layer B was forming?
An extinction/mass extinction
Which is most likely to fossilize: a clam or a jellyfish?
WHY?
Clam - clams have hard shells that can be preserved in sediment, while jellyfish have soft tissue that breaks down more quickly