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Age of the Earth

Age of the Earth. How Old is the Earth?. 1654: Archbishop James Ussher of Ireland studied the timing of biblical events described in the Old Testament, and concluded that the world was created on - October 23, 4004 B.C.E. at 9:00 AM.

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Age of the Earth

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  1. Age of the Earth

  2. How Old is the Earth? 1654: Archbishop James Ussher of Ireland studied the timing of biblical events described in the Old Testament, and concluded that the world was created on - October 23, 4004 B.C.E. at 9:00 AM. Thus, the age of the earth, based on Ussher's results, would be: 4004 + 2003 = 6,007 years old. Many calculations of this type have been done by other biblical scholars, and in general, the Earth was found to be about 6,000 years old based on these types of calculations.

  3. Current Estimate of the Age of the Earth Scientific methods of estimating the age of the earth are based on analysis of evidence found in rocks and on radiometric dating . Based on these methods, scientists have concluded that the earth is much more than 6,000 years old.   Recent estimates of the age of the earth: 4.6 billion years old (4.6 billion = 4,600,000,000)

  4. Geology and Geophysics Geology is the science that deals with the history of the earth as recorded in rocks.

  5. Geologic Time Geologic time is measured in millions of years. How do we know about such long periods of time? Geochronology: The science of determining the ages of rocks.

  6. Absolute Age of the Earth During the 16, 17 and 1800's geologists developed a geologic time scale based on relative ages. But: What about absolute ages? What is the absolute age of the earth? Define: Absolute age of the earth = amount of time since the earth solidified. At some point in the earth's early history, the entire planet was a mass of molten rock material. When did the earth cool and solidify into its present state?

  7. Methods for Estimating the Age of the Earth: • Fossils and evolution • Rates of deposition of sediments • Cooling of the Earth from a molten state • Radiometric Dating

  8. Fossils and Evolution • Fossils = remains of ancient life. • For example, molds of ancient sea shells.    • Mid-1800's: • Charles Lyell - Used evolution to estimate absolute ages of rocks.

  9. Fossils and Evolution To estimate ages of rocks: Need to find a natural process that leaves a tangible record in the rocks. Then: if you can estimate the amount of time associated with that process, the age of the rock can be estimated. Evolution is such a process. Amphistium

  10. Fossils and Evolution How long a period of time would be required for the evolution observed in the rock strata to occur? General conclusion based on this type of approach to estimating age of earth: Earth is at least 10's of millions of years old.

  11. Rates of Deposition of Sediments TT = total thickness of sedimentary strata that has been deposited during earth history. Age of Earth = TT/R

  12. Rates of Deposition of Sediments Because of poor estimates of rates of deposition, this method gave a very wide range of results. But, this method generally suggests that the earth isat least 10's of millions of years old, and (based on both fossil evidence and rates of deposition of sediments): Many geologists and biologists in the 1800's concluded that the earth was several hundreds of millions of years old.

  13. Cooling of the Earth from a Molten State Kelvin's Analysis: Assume that the Earth cooled from a molten state. Assume that cooling followed ordinary laws of heat conduction and radiation (uniformitarianism). Apply laws of heat conduction and radiation, and calculate the number of years it would take for the earth to cool from a hot molten mass to it's present state. Kelvin's Result: Earth is24 to 40 million years old.

  14. Uniformitarianism The Principle of Uniformitarianism The physical, chemical and biological laws that operate today have also operated in the geologic past.

  15. Radioactivity • Discovery of radioactivityin the 1890's showed that the geologists and biologists were right: • Radioactivity as an internal heat source. • Radiometric dating. • So, earth is much older than Kelvin thought…

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