Vocabulary
The actual numerical value to tell how old something is
Absolute Age
A fossil formed in ice
Freezing
Why is radioactive decay used to determine the absolute age of rocks?
Radioactive decay happens at a relatively constant rate
What is a coprolite?
fossilized dung or waste
To tell how old an object is in relation to the objects around it
Relative Age
A fossil formed in tar
Tar seeps
What is a gastrolith
A stone that was inside a dinosaur
A glacial lake deposit is called what
Varve
The principle that Earth’s history can be explained by current geologic processes is
Uniformitarianism
What is amber?
a fossil trapped in tree sap
How many years are resented by a single varve?
1
Index fossil should have what kind of lifespan
Short-lived
What is the law of cross cutting?
A fault or body of rock is younger than any other body of rock it cuts through
What is mummification?
The way fossils are formed in very dry places
Describe each of the 5 ways fossils form
Mummification-drying
Amber-trapped in tree sap
Tar seep-trapped and preserved in tar
Freezing-Frozen in ice or soil
Petrification- Original tissue is replaced by minerals
A frozen organism does not decay because......
Bacteria cannot survive the freezing temperatures
What is the law of super position?
Younger layers of undisturbed sedimentary rock are above older layers
What is petrification?
Original tissues replaced by minerals
How do geologists use the law of superposition and the law of crosscutting relationships to determine the relative ages of disrupted or eroded rock layers?
If the fault cuts through rock layers or other rock features, fault is younger than the rocks it cuts through.
Fossils are discovered in what kind of rock?
Sedimentary