Geologic Time
This principle states that the same geological processes we observe today have operated throughout Earth's history.
What is uniformitarianism?
Fossils that show the activities of an organism, such as footprints or burrows.
What are trace fossils?
This law states that in undisturbed layers of rock, the oldest layers are on the bottom.
What is the Law of Superposition?
This dating method measures the decay of radioactive isotopes to determine a rock's exact age.
What is absolute dating?
This is what is measured using radiometric dating.
What is daughter isotopes?
These remains or impressions of ancient organisms provide evidence for geologic change over time.
What are fossils?
These fossils help scientists determine the relative age of rock layers.
What are index fossils?
This law states that rocks are originally deposited in a specific orientation
What is law of original horizontality?
After three half-lives, this percent of the original parent isotope remains.
What is 12.5%
In absolute dating, these are used to find exact age of rocks.
What are half-lives
The type of rock where most fossils are found.
What is sedimentary rock?
Fossils provide evidence for this process that occurs when layers of Earth’s crust shift over time.
What is plate tectonics?
If a fault cuts through rock layers, it is younger than the layers it cuts through.
What is the Law of Crosscutting?
The process in which unstable atoms lose energy and change into different isotopes over time.
What is radioactive decay?
If a sample starts with 20 g of a certain isotope and after 10 minutes only has 5 g of that isotope, then this number of half-lives have passed.
What is 2?
Fossils are one piece of evidence supporting this phenomenon involving the movement of Earth's land masses.
What is continental drift?
An example of a trace fossil created by a prehistoric creature walking in mud.
What are tracks?
To be considered an index fossil, an organism must have lived during a relatively short and specific period and been found in this abundance.
What is widespread?
To determine the age of a rock, scientists count the number of these that have occurred.
What are half-lives?
In the 1830s, an English scientist proposed the idea of uniformitarianism to describe the process of geologic change on Earth. This word is most closely associated with uniformitarianism.
A. Catastrophic B. Gradual. C. Rare D. Sudden
What is gradual?