GEOLOGIC TIMESCALE: Relative and Absolute Dating

Topic 13​

Geologic Time Scale​: Relative and Absolute Dating

Topic 13​: Geologic Time: Relative and Absolute

The methods used by Geologist in determining the age of rocks and fossils which lead to the creation of the geologic time scale.​

Topic 13​: Geologic Time: Relative and Absolute

Geologic Time Scale

---a timeline that illustrate Earth's history based on geologic events and life forms.

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---this is a system that chronologically relates geological strata (stratigraphy) to time.​

Topic 13​: Geologic Time: Relative and Absolute

The table of geologic periods, presented here, agree with the nomenclature, dates, and standard color codes set forth by the

INTERNATIONAL COMMISION ON STRATIGRAPHY (ICS)

Topic 13​: Geologic Time: Relative and Absolute

4 major Divisions of the Geologic Time Line​.

1. EON

2. ERA

3. PERIOD

4. EPOCH​

STRATIGRAPHY

the correlation and classification of rocks strata.​

Topic 13​: Geologic Time: Relative and Absolute

EON

---The largest time span of the geologic time scale.​

Geologic Time is divided into two EONS

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A. Precambrian Eon​

---refers to the earliest part of Earth's history

B. Phanerozoic Eon

---the current geologic eon in the geologic time scale​

Topic 14​: Geologic Time: Relative and Absolute

---occurred 4.6 billion years ago.​ During this time, the solar system was forming within a cloud of dust and gas known as the solar nebula, which eventually spawned planets and etc.​

---The Earth started cooling and outer edge of the planet solidified from molten lava to solidified crust. Water rained from the atmosphere and created oceans.​

Topic 13​: Geologic Time: Relative and Absolute

---Between 4B & 2.5B yrs. ago, the first form of life on our planet was created in the oceans.​

---Earth when or how it happened is unknown but microfossils of this time indicate that life began in the oceans about 3.5B to 2.8B yrs. ago

​ ----By the end of the Archean, the ocean floor was covered in living mat of bacterial life​.

Topic 13​: Geologic Time: Relative and Absolute

---also called the "Age of Hidden Life" started 2.5B yrs. ago. In this time Enough shield rock had formed to start recognizable geologic processes such as plate tectonics.

---contain many definite traces of primitive life-forms-the fossil remains of bacteria and blue-algae, as well as of the first oxygen-dependent animals.​

Topic 13​: Geologic Time: Relative and Absolute

---The time in which abundant of animal and plant life has existed. It covers 541M yrs to present.

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The Phanerozoic eon is subdivided into three ERA:

PALEOZOIC ERA

MESOZOIC ERA

CENOZOIC ERA​

Topic 13​: Geologic Time: Relative and Absolute

​PALEOZOIC ERA

---the era ran from about 542M yrs. ago to 251M yrs. ago.​

The era began with the break up of one supercontinent and the formation of another, because of this plant became widespread.

divided into 6 period​

-Permian

-Carboniferous

-Devonian

-Silurian

-Ordovician

-Cambrian​

Topic 13​: Geologic Time: Relative and Absolute

​PALEOZOIC ERA

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#Cambrian Period

​ (53M yrs. ago)

known for ushering in an explosion of life on Earth. This Cambrian Explosion​ included the evolution of arthropods (ancestor of today's insects and crustaceans) and chordates (animals with rudimentary spinal cords).

Topic 13​: Geologic Time: Relative and Absolute

​PALEOZOIC ERA

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#Ordovician Period

​ (45M yrs. ago)

-marked in the fossil record by an abundance of marine invertebrates. Perhaps the most famous of these invertebrates was the trilobites, an armored arthropods that scuttled around the seafloor for about 270M yrs. before going to extinct​.

Topic 13​: Geologic Time: Relative and Absolute

​PALEOZOIC ERA

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#Silurian Period

​ (443M 416M yrs. ago)

-saw the spread of jawless fish throughout the seas. Mollusks and corals thrived in the oceans and land: the first undisputed evidence of terrestrial life.

This was the time when plants evolved through they most likely did not yet have leaves or vascular tissue to sip up water and nutrients.​

Topic 13​: Geologic Time: Relative and Absolute

​PALEOZOIC ERA

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#Carboniferous Period

​ (359M 299M yrs. ago)

-long before birds evolved, tetrapods began laying eggs on land for the first time during this period, allowing them to break away from amphibious lifestyle.

Tetrapods were becoming more specialized and two new groups of animals evolved. The first were marine reptiles, including lizards and snakes.

The second were the archosaurs which would give rise to crocodiles, dinosaurs. Most creepily this period is sometimes referred to as the "Age of the Cockroaches" because roaches ancient ancestor was found all across the globe during the carboniferous.

Topic 13​: Geologic Time: Relative and Absolute

​PALEOZOIC ERA

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#Carboniferous Period

​ (299M-251M yrs. ago)

-This period would end with largest mass extinction ever: The Permian extinction.​

Before the Permian mass extinction,​ through the warm seas teemed with life. Coral reefs flourished, providing shelter fish and shelled creatures such as nautiloids and ammonoids.

Modern conifers and ginkgo trees evolved on land. The terrestrial vertebrates evolved to become herbivores, taking advantage​ of the new plant life that had colonized the land.

Topic 13​: Geologic Time: Relative and Absolute

​MESOZOIC ERA

​---Contains the Triassic, Jurassic, and Cretaceous periods.​

The period which spans from about 252M yrs. ago to about 66M yrs. ago was also known as the age of reptiles or the age of Dinosaurs because of its famous inhabitants​.

The Middle Life Era, life diversified rapidly and giants reptiles and other monstrous beast roamed the Earth​

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Topic 13​: Geologic Time: Relative and Absolute

​MESOZOIC ERA

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#Triasic Period

​ (252M-200M yrs. ago)

-saw the rise of reptiles and the first dinosaurs

Topic 13​: Geologic Time: Relative and Absolute

​MESOZOIC ERA

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#Jurassic Period

​ (200M-145M yrs. ago)

-marked by the presence of dinosaurs and first appearance birds.

Topic 13​: Geologic Time: Relative and Absolute

​MESOZOIC ERA

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#Cretaceous Period

​ (145M-66M yrs. ago)

-known for its iconic dinosaurs, such as Triceraptops, and Pterosaurs such as Pteranodon.

Topic 13​: Geologic Time: Relative and Absolute

​CENOZOIC ERA

​---Divided into Paleogene. Neogene, and Quaternary

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