A fossil is the trace or the remains of an organism (shell, bone, tooth, leaf, seed, whole organism, etc.) that lived in a previous geological era. It is generally preserved in sedimentary rocks.
All living organisms that have ever lived on Earth are no longer necessarily present today. Indeed, on a geological time scale, animal and plant populations appear and disappear, often influenced by environmental conditions. To document the history of life on Earth, scientists use traces left by living organisms that once populated the planet. These traces, called fossils, are studied by paleontologists. The science that studies prehistoric life is therefore referred to as paleontology.
Fossil and fossil energy are not to be confused. Fossil energy refers to the energy produced from rocks resulting from the fossilization of living things: oil, coal, and natural gas. The formation of this fossil energy is complex, as a large quantity of organic matter, either dead animals or dead plants, quickly embedded under a layer of soil. Subsequently, a fermentation process combined with a strong pressure of the soil layer on the organic matter transforms it into fossil energy.
Fossilization refers to the transformation of a living organism into a fossil.
Fossilization is a very long process. Usually, when an organism dies, its body quickly decomposes. However, sometimes the remains of an organism are placed in conditions that promote their preservation. The remains are then said to fossilize.
The fossilization of a living being takes place over several stages. First, a living organism dies and settles on the lithosphere’s surface, either in the open air or on the ocean floor. The soft tissues are then broken down within a short period of time. On the other hand, the hard parts (bones, osseous tissue, scales, teeth, etc.) are quickly covered with sediment, which prevents their dispersion. As the sediment accumulates, it hardens and turns into sedimentary rock where the remains of the living organisms will be fossilized. The fossil can therefore be preserved without deteriorating.
Most often, fossils are found in sedimentary rocks. However, a fossil can also be preserved in ice or in a vegetable resin such as amber. It should be noted that only a small percentage of animals and plants are preserved in the fossil state. The vast majority decompose without leaving any trace.
Some fossils are exceptionally rare, sometimes deserving to be disclosed to the scientific community and the general public. This is the case when new specimens are found. It happens in such cases that the fossils are to be exhibited . However, given the rarity of the fossil, it is sometimes wise to reproduce the fossil and keep the original in a safe place.
In the world, there are places where a significant concentration of fossils can be found. In some cases, these sites have fossil specimens so large or aesthetically remarkable that they are worth a visit from tourists.
Dinosaur Provincial Park in Alberta (left) and Miguasha National Park in Quebec (right) are two important fossil sites in Canada.
There are four types of fossils, which are characterized by the way in which they were formed.
Petrified fossils are the remains of organisms that harden when fossilized. Only the hard tissues are found. These remains usually retain their original shape.
A fish fossil petrified in a rock.
Moulded fossils have deformed the surrounding rock. Therefore, rather than preserving the hard structures, the sedimentary rocks form a mould of the remains of the organism, which subsequently decompose. The moulds formed can be empty or filled with minerals.
Feathers of archaeopteryx moulded into the rock.
Trapped fossils form when organisms become encased in material that protects them from decay. Their entire body, soft and hard tissues, can then fossilize. Whole mammoths have been found in ice and insects in amber.
Insects trapped in amber.
Fossilized traces are marks left by an organism that once lived on soft ground. This soil has hardened over the years, retaining the traces left by the animal.
Traces of dinosaurs have been preserved by the soil hardening.
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Fossils provide information on the different forms of life that have marked the history of the Earth. They also provide information on the changes that have marked the evolution of the Earth. Their age can be determined by identifying the stratigraphic layers in which they are found.
Therefore, the position of two fossils relative to each other can be used to date them relatively. However, this dating does not provide an exact age of the fossils: it can only help to determine which of the two fossils is older.
Relative dating is a method of classifying fossils from youngest to oldest, without indicating the absolute age.
To accurately identify the age of a fossil, certain elements, such as carbon-14, can be used to determine the exact age of a fossil.
Absolute dating is a method of determining the age of a fossil.
As fossils form at the same time as stratigraphic layers, the principles of continuity and superposition apply. It can therefore be said that the fossils are the same age as the layer in which they are located. Furthermore, it can also be mentioned that the fossils buried in the deepest stratigraphic layers are older than the fossils present in the surface stratigraphic layers.