Pre-Human History Flashcards
Age of the Universe
13.8 Billion Years Old
Age of our Milky Way Galaxy
9 Billion Years Old
Age of our Sun
4.6 Billion Years Old
Age of the Earth
4.54 Billion Years Old
Age of the Moon
4.47 Billion Years Old
THEIA
Date
Meaning
The body that collided with the Earth to create the Moon is sometimes called Theia, from the name of the mythical Greek Titan who was the mother of Selene, the goddess of the Moon.
Scientists date the impact event to 4.47 billion years ago
THEIA EVIDENCE
Angular Momentum
Moon’s surface
Radioactivity
Densities
Why
Earth’s spin and the Moon’s orbit have similar orientations.
Moon samples indicate that the Moon’s surface was once molten.
The stable-isotope ratios of lunar and terrestrial rock are identical, implying a common origin.
The Moon has a relatively small iron core and has a much lower density than Earth.
The Earth has a very large iron core and the highest density of all the planets in the Solar system.
The Earth-Moon system yielded a Moon formed mostly from the mantles of both the Earth and the impactor, while the core of both the impactor and the Earth accretes to the Earth. It is noteworthy that the Earth has the highest density of all the planets in the Solar system; the absorption of the core of the impactor body renders this observation explicable, given the proposed properties of the early Earth and Theia.
PRECAMBRIAN ERA
Meaning
Beginning
Significance
Significant Dates
End
Meaning: ‘before the Cambrian Explosion’. The Precambrian is a supereon that is subdivided into three eons (Hadean, Archean, Proterozoic).
Beginning: the Precambrian spans from the formation of Earth about 4.47 billion years ago (After Theia) and includes the development of Earth’s oceans, early landforms, and all early life.
First single-celled life: A specific date for the origin of life has not been determined. Carbon found in 3.8-billion-year-old rocks (Archean eon) from islands off western Greenland may be of organic origin.
Well-preserved microscopic fossils of bacteria older than 3.46 Ba have been found in Western Australia.
Multi-cellular life: The first complex multicellular life forms seem to have appeared at roughly 1500 Ma
End: hard-shelled creatures appeared toward the end of the Eon, at around 541 Ma, marking the beginning of the Phanerozoic era and making way for the Cambrian explosion.
PRECAMBRIAN DATES
- 47 billion years ago:
- 8-Ba:
- 46 Ba:
1500 Ma:
541 Ma:
- 47 billion years ago Precambrian begins with the formation of the Earth (After Theia)
- 8-Ba Possible organic material rocks from islands off western Greenland
- 46 Ba: Well-preserved microscopic fossils of bacteria
1500 Ma: Multi-cellular life:
541 Ma: hard-shelled creatures appear
THE PRECAMBRIAN
Name it and its Divisions
The Precambrian is a supereon that is subdivided into three eons
Hadean,
Archean,
Proterozoic
PALAEOZOIC
Meaning
Beginning
Significance
End
The Paleozoic Era from the Greek palaios (παλαιός), “old” and zoe (ζωή), “life”, meaning “ancient life” is the earliest of three geologic eras of the current Eon.
Beginning: The Cambrian explosion 541 million years ago witnessed the most rapid and widespread diversification of life in Earth’s history, in which most modern phyla first appeared.
Significance: The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. It brought the earliest forms of sea life, plants, insects, and eventually early reptiles and amphibians.
End: The Paleozoic Era ended with the largest extinction event in the history of Earth, the Permian–Triassic extinction event 251.9 million years ago.
[The Paleozoic Era is subdivided into six geologic periods (from oldest to youngest): the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
PALAEOZOIC ERA
The Six major geologic periods (from oldest to youngest):
Cambrian,
Ordovician,
Silurian,
Devonian,
Carboniferous, and
Permian periods
CURRENT EON
Name
Divisions
Phanerozoic EON
- Paleozoic 541-252Ma
- Mesozoic 252-66Ma
- Cenozoic 66Ma-now
MESOZOIC
Meaning
Beginning
Significance
End
Subdivisions
Mesozoic means “middle life”, deriving from the Greek prefix meso- for “between” and zōon meaning “animal” or “living being”.
It is one of three geologic eras of the current Phanerozoic Eon, preceded by the Paleozoic (“ancient life”) and succeeded by the Cenozoic (“new life”).
Beginning: The Mesozoic Era began in the wake of the Permian–Triassic extinction event 252 million years ago, the largest well-documented mass extinction in Earth’s history.
Significance: The Mesozoic Era, known as the age of reptiles, included the dinosaurs, the first birds, and the earliest small mammals.
End: The Mesozoic ended with the Cretaceous–PaleoGENE extinction event 66 million years ago, the Chicxulub impact, a mass extinction which killed off all non-avian dinosaurs.
Subdivisions: The era is subdivided into three major periods: the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs and stages.
Extinction event 252 million years ago
Name
Significance
Name: Permian–Triassic extinction event
Significance: The largest well-documented mass extinction in Earth’s history. The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover. The Mesozoic Era began in its wake and the age of Reptiles began.
