This principle states that current geologic processes are the same processes that were at work in the past.
What is uniformitarianism?
100
Sedimentary rocks tend to have structures that make finding relative age difficult. These include: graded bedding, cross-beds and this.
What are ripple marks?
100
This form of dating using radioactive decay to measure absolute age in rocks and fossils.
What is radiometric dating?
100
The remains or traces of animals or plants that lived in a previous geologic time.
What are fossils?
100
These fossils occur only in rock layers of a particular geologic age.
What are index fossils?
200
This law states that an undeformed sedimentary rock layer is older than the layers above it and younger than the layers below it.
What is the law of superpositiion
200
This is known as a break in geologic record.
What is unconformity?
200
This is the time it takes half the mass of a given amount of a radioactive parent isotope to decay into its daughter isotopes.
What is a half-life?
200
This is the study of fossils.
What is paleontology?
200
These fossils are evidence of past animal movement such as tracks, footprints, borings and burrows.
What are trace fossils?
300
This principle states that sedimentary rocks left undisturbed will remain in horizontal layers.
What is the principle of horizontality?
300
This type of unconformity occurs when the boundary is between a set of tilted layers and horizontal layers.
What is angular unconformity?
300
Uranium-238 is a parent isotope that's daughter isotope is this.
What is lead-206?
300
Fossilization can occur by mummification, tar seeps, freezing, amber and this.
What is petrification?
300
This type of fossilization occurs when an insect becomes trapped in tree sap.
What is amber?
400
Before Hutton's time, people believed the earth to be this old.
What is 6,000 years old?
400
When there is a boundary between old sedimentary rocks and younger overlying layers that have been deposited and eroded this unconformity exists.
What is disconformity?
400
If a parent isotope contains 10 g of the parent isotope and then is measured to have 5 g after one half-life has passed, this is how much is left after another half-life passes.
What is 2.5 g?
400
These are the types of fossils: carbon films, molds and casts, coprolites and this.
What are gastroliths?
400
These are a common way fossils form when the organism leaves an empty space within hardened sediment that then fills with sand or mud, forming a replica of that once living thing.
What are molds and casts?
500
Earth is believed to be this old.
What is 4.6 billion years old?
500
When stratified rock rests upon unstratified rock this unconformity occurs.
What is nonconformity?
500
If carbon has a half-life of only 5,730 years, you should conclude this about the things it can date.
What is they must be young since it's half-life is so short?
500
These types of fossils are fossilized dung or waster matter.
What are coprolites?
500
This law states that if there is a fault or igneous intrusion in layers of rock, the fault and intrusion are always younger than the rocks they cut through.