Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major...
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![Page 1: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/1.jpg)
Lecture Notes –
Geologic Eras
![Page 2: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/2.jpg)
Geologic TimescaleThe geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era (PC).
o There are not many fossils from the Pre-Cambrian
o but it makes up 80 %
of the earth’s history.
![Page 3: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/3.jpg)
Geologic TimescaleThe three more recent eras the Paleozoic, Mesozoic and Cenozoic Eras:
“-zoic” comes from the Greek word “zoe” which means “life”.
![Page 4: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/4.jpg)
Geologic Timescale“Paleo-” means “ancient”, so Paleozoic means “ancient life”.“Meso-” means “middle”, so Mesozoic means “middle life”.“Ceno-” means “recent”, so Cenozoic means “recent life”.
![Page 5: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/5.jpg)
Geologic TimescaleThe geologic timescale is not like a historical timescale with decades and centuries. There is not a set number of years per time division. Rather, each time division is distinguished by events that happen to signal the “end of an era”.
![Page 6: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/6.jpg)
Geologic TimescaleThe four eras are divided up into 15 periods:3 Pre-Cambrian Periods (PC 4.55 bya to 542 mya
Hadean (pA) - 4.55 – 4.00 bya no life forms
Archean (A) - 4.00 – 2.50 bya bacteria
Proterozoic (PL) - 2.50 – 0.542 bya (542 mya) –
simple life forms
![Page 7: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/7.jpg)
Precambrian Era: 4.6 - .542 b.y.aHadean – 4.55 bya – 4.00 bya • Earth and solar system still forming.• No rocks, except meteorites, are this old.•Great Iron Catastrophe - Molten iron sinks to the core; crust solidifies. This event marks the end of the Hadean Period.
Update: Geologists have found a
4.28 by old rock in northern Quebec. So now there is one rock this old!!
![Page 8: Lecture Notes – Geologic Eras. Geologic Timescale The geologic timetable is divided into 4 major eras: The oldest era is called the Pre-Cambrian Era.](https://reader036.fdocuments.in/reader036/viewer/2022081506/56649ce55503460f949b3110/html5/thumbnails/8.jpg)
Archaeozoic Period – 3.8 bya – 2.5 bya Earliest fossils appeared – bacterial, 3.5 bya
Life forms did not need oxygen - anaerobic
Oxygen was produced by stromatolites: photosynthetic colonies of bacteria.
3.8 bya: oldest known rocks
2.8 bya: 2/3 continents created
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Proterozoic period – 2.5 bya - .542 bya• algae, jellyfish and worms appear 1.5 – 1.0 bya
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Proterozoic period – 2.5 bya - .543 bya Gondwana forms
from Africa, South America, Australia, India and Antarctica - 650 mya
First signs of oxygen build up in the atmosphere 2.5 bya.o Caused the first
major extinction.