1. Friday October 22, 2010
(The Precambrian Eon)

2. The Launch Pad Friday, 10/22/10 Great Permian extinction
Name an important factor that caused the Precambrian Eon to change to the Phanerozoic Eon.
First organisms with shells and other hard body parts
Name an important factor that caused the Paleozoic Era to change to the Mesozoic Era.
Great Permian extinction
Name an important factor that caused the Mesozoic Era to change to the Cenozoic Era.
Extinction of dinosaurs and many other species

3. Announcements
If you need to take or remediate Test 3, please make an appointment with me to do so ASAP.

4. Assignment Currently Open Date of Notes on Website
Pages
Date of Notes on Website
Date Issued
Date Due

6. The Geologic Time Scale
Geologic time is divided into Eons.
Precambrian Eon
Archean Eon
Proterozoic Eon
Phanerozoic Eon

7. The Geologic Time Scale
Eons are further divided into Eras.
Archean Eon
Eoarchean Era
Paleoarchean Era
Mesoarchean Era
Neoarchean Era
Proterozoic Eon
Paleoproterozoic Era
Mesoproterozoic Era
Neoproterozoic Era
Phanerozoic Eon
Paleozoic Era
Mesozoic Era
Cenozoic Era

8. The Geologic Time Scale
The Phanerozoic Eon is further divided into Periods.
Phanerozoic Eon
Paleozoic Era
Cambrian Period
Ordovician Period
Silurian Period
Devonian Period
Carboniferous Mississippian Period
Carboniferous Pennsylvanian Period
Permian Period
Mesozoic Era
Triassic Period
Jurassic Period
Cretaceous Period
Cenozoic Era
Tertiary Period
Quaternary Period

9. The Geologic Time Scale
The Cenozoic Era is further divided into Epochs.
Cenozoic Era
Tertiary Period
Paleocene Epoch
Eocene Epoch
Oligocene Epoch
Miocene Epoch
Pliocene Epoch
Quaternary Period
Pleistocene Epoch
Holocene Epoch

10. Much of Earth’s stable continental crust was created during this time.
The Precambrian Eon
The Precambrian Eon, which is divided into the Archean and the Proterozoic Eons, spans about 88% of Earth’s history.
Much of Earth’s stable continental crust was created during this time.
Partial melting of the mantle formed volcanic island arcs and ocean plateaus.

11. The Precambrian Eon
These crustal fragments collided and accreted to form larger crustal provinces.
Larger crustal areas were assembled into larger blocks called cratons.
Cratons form the core of modern continents.

12. Formation of Continental Crust
According to one model, the growth of large continental masses were accomplished through the collision and accretion of various types of terrains, including volcanic arcs and oceanic plateaus.

13. The Extent of Crustal Materials Remaining From the Archean and Proterozoic Eons

14. Map showing the major geological provinces of North America and their ages in billions of years (Ga). It appears that North America was assembled from crustal blocks that were joined by processes very similar to modern plate tectonics. These ancient collisions produced mountainous belts that include remnant island arcs trapped by colliding continental fragments.

15. The Precambrian Eon The Supercontinents
The supercontinents were large landmasses that consisted of all, or nearly all, of the existing continents.
Pangaea was the most recent supercontinent, but perhaps an even larger one, Rodinia, preceded it.
Splitting and reassembling of supercontinents have generated most of Earth’s major mountain belts.
Supercontinents have also profoundly affected Earth’s climate over time.

16. Possible configuration of the supercontinent Rodinia
Figure 12.15

17. It was during the Precambrian Eon that life first began on the Earth.
Although the Precambrian Eon contains some 88% of Earth's history, its fossil record is poor because organism were soft-bodied during this time, resulting in little remaining evidence.

18. The Precambrian Eon
The majority of Precambrian fossils are stromatolites that are often heavily metamorphosed or deeply buried.
However, preserved cells have been discovered at selective sites, such as the 2.0 Ba Gunflint Formation Jasper stromatolites from Gunflint Formation near Mackies, northern Ontario.

19. The Precambrian Eon
The earliest life forms were prokaryotes that evolved in the seas, possibly as early as 3.8 Ga.
The first primitive prokaryotic single-celled organisms appeared in the oceans in the form of bacteria (eubacteria or Achaea).

20. The Precambrian Eon
Earth’s first living organisms were probably chemotrophs existing in an anoxic world and producing H2S or CO2.

21. The Precambrian Eon
Nearly 3.5 Ga, photosynthezing cyanobacteria began releasing oxygen into the atmosphere as a by-product of the process of photosynthesis.

22. The Precambrian Eon
The first multi-cellular organisms appeared toward the end of the Precambrian Eon, sometime prior to 542 Ma.

23. The Precambrian Eon
When the eukaryotes (single-celled organisms with a nucleus) evolved through endosymbiosis is disputed, with claims as early as 3.4 Ga, but with less equivocal fossils dating from 1.8 to .8 Ga.

24. The Precambrian Eon
With the eukaryotes comes sexual reproduction, enabling genetic diversity and the concomitant ability to adapt to and survive environmental changes.