How do nosotros know the Age of the Earth?
The basis is a constantly changing planet. Its crust is continually beingness created, modified, in addition to destroyed. As a result, rocks that tape its earliest history convey non been institute in addition to likely no longer exist. Nevertheless, in that place is substantial show that the basis in addition to the other bodies of the Solar System are 4.5-4.6 billion years old, in addition to that the Galaxy Galaxy in addition to the Universe are older still. The top dog show for the antiquity of basis in addition to its cosmic environment is:
- The oldest rocks on Earth, institute inward western Greenland, convey been dated yesteryear 4 independent radiometric dating methods at 3.7-3.8 billion years. Rocks 3.4-3.6 billion years inward historic menses convey been institute inward southern Africa, western Australia, in addition to the Great Lakes portion of North America. These oldest rocks are metamorphic rocks but they originated equally lava flows in addition to sedimentary rocks. The debris from which the sedimentary rocks formed must convey come upwards from fifty-fifty older crustal rocks. The oldest dated minerals (4.0-4.2 billion years) are tiny zircon crystals institute inward sedimentary rocks inward western Australia.
The oldest Moon rocks are from the lunar highlands in addition to were formed when the early on lunar crust was partially or solely molten. These rocks, of which simply a few were returned yesteryear the Apollo missions, convey been dated yesteryear ii methods at betwixt 4.4-4.5 billion years inward age.
- The bulk of the lxx well-dated meteorites convey ages of 4.4-4.6 billion years. These meteorites, which are fragments of asteroids in addition to stand upwards for some of the most primitive fabric inward the solar system, convey been dated yesteryear v independent radiometric dating methods.
- The “best” historic menses for the basis is based on the fourth dimension required for the atomic number 82 isotopes inward 4 real erstwhile atomic number 82 ores (galena) to convey evolved from the composition of atomic number 82 at the fourth dimension the Solar System formed, equally recorded inward the Canyon Diablo Fe meteorite. This “model atomic number 82 age” is 4.54 billion years.
- The show for the antiquity of the basis in addition to Solar System is consistent amongst show for an fifty-fifty greater historic menses for the Universe in addition to Galaxy Galaxy. a) The historic menses of the Universe tin hold out estimated from the velocity in addition to distance of galaxies equally the universe expands. The estimates gain from seven to xx billion years, depending on whether the expansion is constant or is slowing due to gravitational attraction. b) The historic menses of the Galaxy is estimated to hold out 14-18 billion years from the charge per unit of measurement of development of stars inward globular clusters, which are idea to hold out the oldest stars inward the Galaxy. The historic menses of the elements inward the Galaxy, based on the production ratios of osmium isotopes inward supernovae in addition to the alter inward that ratio over fourth dimension due to radioactive decay, is 8.6-15.7 billion years. Theoretical considerations signal that the Galaxy formed inside a billion years of the get-go of the Universe. c) Combining the information from a) in addition to b), the “best, i.e., most consistent, historic menses of the universe is estimated to hold out around xiv billion years. For to a greater extent than electrical flow information on the historic menses of the universe, visit NASA’s Planck Mission studies.
|Read about Radiometric dating
Adapted from The Age of the Earth , yesteryear the Branch of Isotope Geology, U.S. Geological Survey, Menlo Park, California