Lec 2: Geologic Time Flashcards
Lecture’s goals:
1_ Recognizes that the geologic processes we see today have acted over very long timescales and can provide us with clues about the process that shaped the Earth in the past.
2_ Apply relative dating principles to interpret the geologic history at an engineering project site.
3_ Compare and contrast relative and absolute dating methods.
4_ Describe what the major divisions of the geologic timescale signify.
Lecture’s goals:
1_ Recognizes that the geologic processes we see today have acted over very long timescales and can provide us with clues about the process that shaped the Earth in the past.
2_ Apply relative dating principles to interpret the geologic history at an engineering project site.
3_ Compare and contrast relative and absolute dating methods.
4_ Describe what the major divisions of the geologic timescale signify.
How many techniques are there to determine geological time?
2, relative dating (19th century) and absolute dating (20 century)
Absolute time units: (3 units)
Ga: giga annum
Ma: mega annum
ka: kilo annum
Major divisions of geologic time scale:
Hadean Eon (4.5-4 Ga)
Archean Eon (4-2.5 Ga)
Proterozoic Eon (2.5 Ga-545 Ma)
Phanerozoic Eon (<545 Ma “visible life”)
How would you describe the Hadean Eon (4.5-4 Ga)?
It’s the earth’s cooling period
Widespread volcanism
How would you describe the Archean Eon (4-2.5Ga)?
It’s the age of bacteria
oldest rocks found on the planet
final stages of earth cooling and formation of the crust
How would you describe the Proterozoic Eon (2.5Ga-545 Ma)?
Most diamonds formed
oldest sedimentary rocks
formation of the ozone layer
first jellyfish
How would you describe the Phanerozoic Eon (<545 Ma)?
Age of marine, reptiles, and mammals
Lecture’s goals:
1_ Recognizes that the geologic processes we see today have acted over very long timescales and can provide us with clues about the process that shaped the Earth in the past.
The principles we can apply to identify which rock section are
- Younger above - Older below;
- Intrusion and Faults are younger than the rocks they intrude or break.
Lecture’s goals:
2_ How to apply relative dating principles to interpret the geologic history at an engineering project site? (hint: 2)
1: observe contact relationships between rock units
2: fossil record
Lecture’s goals:
3_ Compare and contrast relative and absolute dating methods.
Relative dating tells how rocks are older or younger by comparing them with others;
Absolute dating uses radiometrics.
Lecture’s goals:
4_ Describe what the major divisions of the geologic timescale signify.
_ Hadean Eon (earth’s cooling period)
_ Archean Eon (“age of bacteria”)
_ Proterozoic Eon (oldest sedimentary rocks)
_ Phaerozoic Eon ( Visible life)
