Super continents and Geological Timescale

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Super Continents

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• Most of Florida and southern Georgia and Alabama is underlain by rocks that were originally part of Gondwana, but this region stayed attached to North America when the Central Atlantic opened.

• ​Pangaea, Gondwanaland, Laurasia and Tethys. a large supercontinent that existed existed ~225 million years ago at the .. between the close of the Paleozoic and start of the Mesozois (at the Permo-Triassic).​

 

• The oldest of the supercontinents is called Rodinia and was formed during Precambrian time some one billion years ago. ​​

 

• Another Pangea-like supercontinent, Pannotia, was assembled 600 million years ago, at the end of the Precambrian. Present-day plate motions are bringing the continents together once again.

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​https://www.britannica.com/place/Gondwana-supercontinent

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COntinental Drift

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Continental Drift: the gradual movement of the continents across the earth's surface through geological time.

​https://socratic.org/questions/how-does-the-fossil-record-support-the-theory-of-continental-drift

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Geological Timescale

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http://www.geologyin.com/2016/12/10-interesting-facts-about-geological.html
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​http://www.vce.bioninja.com.au/aos-4-change-over-time/evolution/geological-time-scale.html

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Mass Extinctions

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​The big five mass extinctions
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• Biologists suspect we're living through the sixth major mass extinction. ...
• Late Devonian, 375 million years ago, 75% of species lost. ...
• End Permian, 251 million years ago, 96% of species lost. ...
• End Triassic, 200 million years ago, 80% of species lost. ...
• End Cretaceous, 66 million years ago, 76% of all species lost.

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The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction, was a sudden mass extinction of some three-quarters of the plant and animal species on Earth, approximately 66 million years ago.
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What is Time?

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• Biological changes happen over millions of years.

• Time is something that we agree on, not a mandate of the universe, it is relative, if one says "a day" it is valid to say : "a day according to who?" 

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• We currently measure time using Cesium 133, the element most commonly chosen for atomic clocks: 

 

• https://science.howstuffworks.com/atomic-clock3.htm​

 

• Atomic Clock - A precision clock that depends for its operation on an electrical oscillator regulated by the natural vibration frequencies of an atomic system (as a beam of cesium atoms)

 

• Atom - The smallest particle of an element that can exist either alone or in combination; the atom is considered to be a source of vast potential energy

 

• Cesium 133 - An isotope of cesium used especially in atomic clocks and one of whose atomic transitions is used as a scientific time standard

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• ​SI Second (atomic second) - The interval of time taken to complete 9,192,631,770 oscillations of the cesium 133 atom exposed to a suitable excitation

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