Anonymous asked in Science & MathematicsEarth Sciences & Geology · 2 months ago

Why are fossil dates not always accurate? How do scientists attempt to get the most reliable date possible?

2 Answers

  • 2 months ago
    Favourite answer

    There are 3 methods of dating fossils. One method is the relative dating detailed in the first answer which does have some major problems with a few exceptions. When a meteorite impacts Earth. 5he mass, speed and angle of the meteorite has a force which heats the ground it impacts very quickly to very high temperatures that creates new minerals at very pressures lightning strikes can do this too. Depending on the force of the impact, that can create a dean debt is clouds or impact ash cloud that can cover a large part of the world and create an impact winter. This?us?what happened when the Chicxulub me for that was 10 kilometers or 6 .17 miles in diameter impacted the Yucatan Peninsula 63 to 66 million years ago. It was the impact winter that caused the extinction of 70 to 80% of all the species on Earth at that ytime, including many of the large dinosaurs, but NOT ALLdinosaurs. Birds I are modern day dinosaurs along with several reptiles. 

    The ash layer from that impact contains an isotope of iridium that is Not common on Earth. That tritium isotope and ash layer is what divides the Mesozoic era from the Cenozoic era. At the same tine as the impact there were volcanoes erupting in India creating the Deccan basalt and Siberia. That created hash clouds that went almost worked?wide and are found in ice cores in the Arctic and glaciers world wide, including Antarctica. 

    The other dating method is radiometric isotope dating. This includes carbon 14 dating, but there are significant problems?with Carbon 14, mainly its relatively short half life of 5790 years. There are other radioactive isotopes with significantly linger half lives, like potassium argon 40, europium - samarium, uranium 238 to Uranium 235 to lead 208 and lead 206. You can read the Wikipedia article for a more detailed answer. This is called absolute dating , but since there is margin of error of several million years either way, it is not as precise.


    Source(s): sciences/geology, M.S. ABT geophysics, B.S. physical geogtaphy, M.S. geology. Graduate level radioisotope class spring 1998.
  • 2 months ago

    The big problem is that fossils occur in sediments, and the methods for dating that we can use are not very reliable in sediments.  This is because sediments are made up of rock bits from all over, and thus have a wide range in actual dates of original formation (when we date, we get a date for when the mineral cooled down from some high temperature and set the clock).  We don't have any reliable methods to date the timing of the deposition of a sediment, except in very recent sediments, ones that have not even been turned onto rock, for the most part.

    Dating a sediment requires putting limits on age by its relationships with other things which we can date.  Sometimes, the constraint is very poor, there are no good datable rocktypes of similar age.  There are situations where a detrital or chemical sediment can be dated, but it requires some pretty unusual circumstances.

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