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Patterns in Time – Deep Time Concepts and… Evolution

Patterns in Time – Deep Time Concepts and… Evolution. “… it is highly important for us to gain some notion, however imperfect, of the lapse of years.” Charles Darwin: On the Origin of Species 1859 Chapter 9: On the Imperfection of the Geological Record.

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Patterns in Time – Deep Time Concepts and… Evolution

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  1. Patterns in Time – Deep Time Concepts and… Evolution “… it is highly important for us to gain some notion, however imperfect, of the lapse of years.” Charles Darwin: On the Origin of Species 1859Chapter 9: On the Imperfection of the Geological Record

  2. A MAJOR key to learning about the history of life is relative dating(no, I don’t mean dating your cousin) • Relative dating -The proper chronological placement of a feature, object, or happening in the geologic time scale without reference to its absolute age.

  3. What about FOR SURE dates?This is called absolute dating (although you could call marriage absolute dating…there is only one person you date) • Absolute dating - used by geologists to determine the actual age of a material. It can be achieved through the use of historical records and through the analysis of biological and geological patterns. • Some archaeologists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies a certainty and precision that is rarely possible in archaeology.

  4. Okay, so then this radiometric dating is…?(not some sort of interspecies thing) • Radiometric dating is based on the constant rate of decay of radioactive isotopes. • Radioactive isotopes are atoms that have a bit too much weight on them (kind of like most Americans). Some of the most typically referenced ones are carbon-14 and uranium-238.

  5. Half-life (also what my husband says he lived before he met me ) • If an atom is unstable (also known as (aka) radioactive), then the bit extra it is carrying is extra protons (or neutrons). • As time passes, the extra protons/neutrons get lost until the element is changed into a “new” one. • In the case of carbon-14 it becomes carbon-12. • With uranium-238, though, it becomes lead-206…a totally different element. • Half-life is the time it takes for HALF of the element to change.

  6. So…what’s the deal on this? • A geologic eon is the largest division of time in geology, and is generally considered to be around a billion years • Eras – a very long span of geological time • Periods - a unit of geological time during which a system of rocks formed • Epochs – the “shortest” time division in geologic history

  7. Where to go for info • www.enchantedlearning.com • Search for “Geologic time scale”

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