Relative Dating
This principle states that in an undisturbed sequence of sedimentary rock layers, the oldest layer is at the bottom.
What is the Law of Superposition?
This is the preserved remains, impressions, or traces of ancient organisms.
What is a fossil?
This is a trait that helps an organism survive and reproduce in its environment.
What is an adaptation?
This is the spontaneous breakdown of unstable atomic nuclei, releasing radiation.
What is radioactivity?
This is a gap in the geologic record caused by erosion or a period when rock was not deposited.
What is an unconformity?
This type of fossil is especially useful for determining the relative age of rock layers because the organism existed for a relatively short period and was widespread.
What is an index fossil?
This process occurs when organisms with traits that provide advantages are more likely to survive and reproduce.
What is natural selection?
This is the amount of time required for half of the radioactive atoms in a sample to decay.
What is a half-life?
This principle states that sedimentary rock layers are originally deposited in relatively flat, horizontal layers.
What is the Principle of Original Horizontality?
This principle states that fossil organisms succeed one another in a definite and recognizable order through geologic time.
What is the Principle of Fossil Succession?
This is the change in inherited characteristics of populations over generations.
What is evolution?
This method uses the predictable decay of radioactive isotopes to determine the numerical age of rocks or other materials.
What is radiometric dating?
This principle states that a feature that cuts through another rock is younger than the rock it cuts.
What is the Principle of Cross-Cutting Relationships?
This is the largest division of geologic time.
What is an eon?
An organism is described this way when no members of its species are still alive.
What does extinct mean?
This dating method uses the radioactive isotope carbon-14 to determine the age of once-living materials.
What is radiocarbon dating?
This method determines whether a rock or event is older or younger than another without determining its exact numerical age.
What is relative dating?
This division of geologic time is smaller than an eon but larger than a period.
What is an era?
This principle states that the same natural processes operating today have operated in similar ways throughout Earth's history.
What is uniformitarianism?
In geology, this process involves matching rock layers or fossils from different locations to determine their relative relationships in time.
What is correlation?