But what is exactly a fossil and how is it formed? Have you ever wondered how science knows the age of a fossil? Read on to find out! If you think of a fossil, surely the first thing that comes to your mind is a dinosaur bone or a petrified shell that you found in the forest, but a fossil is much more.
So, there are different types of fossils:. Petrified fossil of horseshoe crab and its footsteps. Mireia Querol Rovira Ichnofossils trace fossils: Mireia Querol Rovira Amber: Mireia Querol Rovira Chemical fossils: This is the case of our recent ancestors Chalcolithic.
He lived during the Chalcolithic Copper Age and died years ago. Wikimedia Commons Living fossils: The most famous case is the coelacanthit was believed extinct for 65 million years until it was rediscovered inbut there are other examples such as nautilus.
Comparison between the shell of a current nautilus left with an ammonite of millions of years old right. Mireia Rovira Querol Pseudofossils: The best known case is pyrolusite dendrites that seem plants.
Pirolusita infiltrations in limestone.
Mireia Querol Obviously fossils became more common after the appearance of hard parts shells, teeth, bones …million years ago Cambrian Explosion.
The fossil record prior to this period is very scarce. The science of fossils is Paleontology. To determine the age of fossils there are indirect methods relative dating and direct absolute dating.
The fossils are dated according to the context in which they are found, if they are associated with other fossils guide fossils or objects of known age and it depends on the stratum they are found. This methods are more accurate and are based on the physical characteristics of matter.
They are based on the rate of decay of radioactive isotopes in rocks and fossils. I sotopes are atoms of the same element but with different number of neutrons in their nuclei. Radioactive isotopes are unstable, so they are transformed into a more What does absolute dating mean in biology ones at a rate known to scientists emitting radiation.
Unknown author Radiocarbon Carbon Knowing the difference between C12 and C14 of the sample, we can date when the organism died. The maximum limit of this method are 60, years, therefore only applies to recent fossils.
Some minerals have magnetic properties and are directed towards the north magnetic pole when in aqueous suspension, for example clays. But when laid on the ground, they are fixed to the position that the north magnetic pole was at the time.
If we look at what coordinates are oriented such minerals at the site, we can associate it with a particular time.
This dating is used on clay remains and as the magnetic north pole has been several times in the same geographical coordinates, you get more than one date. Depending on the context of the site, you may discard some dates to reach a final dating.