Principles
What principle states that sedimentary rocks are deposited in horizontal layers?
Original Horizontality
What method uses carbon-14 to date organic materials?
Radiocarbon Dating
What is uniformitarianism?
The idea that geological processes occurring today have occurred since Earth formed
What is the name for a break in the rock record caused by erosion?
Unconformity
What are alternating layers of light and dark sediments called?
Varves
Which scientist’s work laid the foundation for uniformitarianism?
James Hutton
Which type of unconformity occurs when sedimentary rocks lie above igneous rocks?
Nonconformity
What is the term for the numerical age of rocks?
Absolute Age Dating
What is a half-life?
The time it takes for half of a radioactive isotope to decay
What does the principle of superposition state?
Oldest layers are on the bottom
What is dendrochronology used for?
Studying tree rings to determine the absolute age
How old do some scientists believe the Earth is based on radiometric dating?
4.6 billion years
What principle helps geologists match rock layers in different locations?
Correlation
What is an angular unconformity?
A gap in the rock record where tilted layers are overlain by horizontal layers
What does the geologic time scale show?
The history of life