What are fossils and hoe is age of fossils determinded?
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A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants.
The age of fossils is determined through relative dating, and objective dating.
Fossils themselves usually can’t be directly dated, because most of them have little or no of the organic material left, and dating by Carbon 14 is only useful up to around 35000–50000 years. Fossils older than that must be dated by the rock layer in which they are found.
Fortunately, scientists have been studying rock strata for over 300 years, and have worked out very precisely the order in which the rock layers have been laid down. Very roughly, rocks are ranked in eras from oldest to youngest:
PreCambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene. Throughout the world, rocks are always found in this order, unless there’s been some obvious disturbance. This allows scientists to place a fossil found within a particular rock layer within these particular age brackets.
The only problem with this, is that knowing which layer is older than the next doesn’t give us an objective date for the rock layer. We can only know, from the above, that a cretaceous fossil is younger than a Jurassic one.
What allows scientists to put an objective date is radiometric dating. Sedimentary rock, which the vast majority of fossils are encased in, can’t be dated directly, but igneous rock can be. By measuring the amount of radioactive decay in particular elements since the igneous rock solidified, one can work out a fairly precise date for the rock. If you find a igneous layer dated at 2.4 million years old on top of a sedimentary layer you can be sure the sedimentary rock was laid down before 2.4 million years ago. A second igneous layer below dated to 3.2 million years, tells you that the sediment was laid down between 3.2 and 2.4 million years ago. A fossil within that layer then must be older than 2.4 million years, and younger than 3.2 million years.
The most commonly used elements for radiometric dating of rocks are Argon, Uranium, Potassium, and Rubidium because they have fairly long half life. Carbon isn’t used for dating rocks because it’s half life is too short.
I think this will help you.
The age of fossils is determined through relative dating, and objective dating.
Fossils themselves usually can’t be directly dated, because most of them have little or no of the organic material left, and dating by Carbon 14 is only useful up to around 35000–50000 years. Fossils older than that must be dated by the rock layer in which they are found.
Fortunately, scientists have been studying rock strata for over 300 years, and have worked out very precisely the order in which the rock layers have been laid down. Very roughly, rocks are ranked in eras from oldest to youngest:
PreCambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene. Throughout the world, rocks are always found in this order, unless there’s been some obvious disturbance. This allows scientists to place a fossil found within a particular rock layer within these particular age brackets.
The only problem with this, is that knowing which layer is older than the next doesn’t give us an objective date for the rock layer. We can only know, from the above, that a cretaceous fossil is younger than a Jurassic one.
What allows scientists to put an objective date is radiometric dating. Sedimentary rock, which the vast majority of fossils are encased in, can’t be dated directly, but igneous rock can be. By measuring the amount of radioactive decay in particular elements since the igneous rock solidified, one can work out a fairly precise date for the rock. If you find a igneous layer dated at 2.4 million years old on top of a sedimentary layer you can be sure the sedimentary rock was laid down before 2.4 million years ago. A second igneous layer below dated to 3.2 million years, tells you that the sediment was laid down between 3.2 and 2.4 million years ago. A fossil within that layer then must be older than 2.4 million years, and younger than 3.2 million years.
The most commonly used elements for radiometric dating of rocks are Argon, Uranium, Potassium, and Rubidium because they have fairly long half life. Carbon isn’t used for dating rocks because it’s half life is too short.
I think this will help you.
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Fossils are the buried remains of dead plants and organisms .
The age of Fossils are determined by
1. Radioactive Dating
2. Their location : If they are located deep inside the Earth they are older one . But if they are not so Deep they are recent ones
The age of Fossils are determined by
1. Radioactive Dating
2. Their location : If they are located deep inside the Earth they are older one . But if they are not so Deep they are recent ones
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