Chapter 11: Geologic Time Flashcards
Who led the expedition in 1869 through the Grand Canyon?
John Wesley Powell
A Scottish physician who is known as “founder of modern geology” and published the “Theory of Earth” in late 1700’s
James Hutton
“the present is the key to the past.”
What is relative dating?
means placing rocks and geologic events in order of their occurrence
The 3 Principles and Rules of Relative Dating
1) Law of Superposition- sequence of rocks, oldest are on the bottom
2) Principle of Original Horizontality- all sediment originally deposited horizontally.
3) Principle of Cross-Cutting Relationships- younger features cut through older features
4) Law of Inclusions- inclusions are older than rock which they included
A break of gap in a geologic rock record is called what?
Unconformity
Three types of Unconformity
A) Angular Unconformity- tilted/ folded rocks that are over-laying other rocks
B) Disconformity- geologic time missing from rock. Due to period of erosion (present in Emporia)
C) Nonconformity- younger sedimentary rocks over-lays older metamorphic or igneous rocks
The four subdivisions of the Geologic Time Scale?
- Eons- greatest expanse of time
- Eras- subdivisions of an eon
- Periods- era subdivided into periods
Cenozoic (recent)
Mesozoic (middle)
Paleozoic (ancient) - Epochs- periods further divided into epochs
Conditions that favor preservation?
1) rapid burial
2) organisms w/ hard parts (bone or shell)
Jellyfish, worms, soft creatures don’t preserve well because they are soft and not hard
Principle of Fossil Succession is?
A) Fossils succeed one another in a definite/ determinable order
B) Proposed by William Smith
EX: dinos lived before people
What is an Index Fossil?
1) geographically widespread
2) Existed for a short range of geologic time
A fossil can be used as an “index marker” for specific time period.
