Fossils
What is a fossil?
The trace or remains of an organism that lived long ago.
According to the Law of Superposition, which rock layer is the YOUNGEST?
The top layer
What is the difference between relative dating and absolute dating?
Relative dating is determining whether an object or event is older or younger than other objects or events. Absolute dating is determining the actual age of an event or object in years.
The geologic time scale divides Earth's history into intervals of time defined by major events. These intervals are further divided into periods, eons, epochs, and eras. Which represents the largest unit of time?
Eon
The scientific study of the origin, history, and structure of Earth and the processes that shape it.
Geology
Which is more common to find, a trace fossil or a body fossil? Why?
Trace fossil; one organism can leave behind thousands of trace fossils in their lifetime, but will only leave behind one body when they die.
According to the law of crosscutting relationships, a fault or body of rock, such as an intrusion, must be (younger/older) than any layer of rock that it cuts through.
Younger
If you are trying to find the absolute age of a rock sample that is 5,000 years old, what method of radiometric dating would you use?
Radiocarbon dating
Explain the difference between the principle of uniformitarianism and catastrophism.
Uniformitarianism is the idea that the same geologic processes that shape Earth today have been at work throughout Earth's history and they change Earth gradually. Catastrophism states that all geologic change occurs suddenly.
A fossilized structure that formed in sedimentary rock by animal activity on or in soft sediment?
Trace fossil
Fossils are most commonly found in what type of rock?
Sedimentary rock
Name one way that rock can be disturbed and explain how it disturbs the rock layers.
Tilting: Earth's forces move rock layers up or down unevenly; Folding: the bending of rocks that can happen when rock layers are squeezed together; Fault: a break or crack in Earth's crust; Intrusion: an igneous rock that forms when magma is injected into rock and then cools; Unconformity: a missing layer of rock
A crystal contains a radioactive isotope that has a half-life of 10,000 years. 25% of the parent isotope remains in the sample. How old is the sample?
20,000 years
What are the three eras in the order in which they occured?
Paleozoic, Mesozoic, Cenozoic
The time needed for half of a sample of a radioactive substance to undergo radioactive decay to form daughter isotopes.
Half-life
What is one material that we can use to tell us about Earth's climate history?
Fossils, tree rings, sea-floor sediments, ice cores
How can fossils be used to determine the relative ages of rock layers?
Arranging fossils based on which formed before others can be used to determine the relative ages of the rock layers the fossils are found in.
If 12.5% of a radioactive sample remains, how many half lives have passed?
What are the first three eons (Hadean, Archean, Proterozoic) collectively called?
Precambrian Time
A radioactive isotope
Parent isotope
Name the FIVE ways in which fossils are preserved.
Trapped in amber, trapped in asphalt, buried in rock, frozen, petrified
How is the geologic column used in relative dating?
To compare and identify relative ages of rock layers that are in different areas.
Name TWO characteristics of index fossils.
Found in large numbers, found over a large area, have distinct features, lived during a short period of time (only found in one layer of rock)
In which era did the continents move to their present day locations, temperatures became extreme from the poles to the equator, and mammals evolve?
The Cenozoic era
A surface that represents a missing part of the geologic column?
Unconformity