Often we tend to talk about dinosaur bones, as if that’s what paleontologists unearth. However, strictly speaking, fossils they are not bones. They are a reflection of what once were the hard parts of a living being, from its bones to its claws, through its shell or its seeds, in the case of plants. But to this day they are only rocks.
Of course, that “solo” does not confuse us or lead us to think that it is a minor thing. Fossils are really interesting rocks, which they give us a lot of information of the living beings that once were.
But going back to the subject of its composition, if they are not bones, how are they formed? The key is in a process called fossilization, which only occurs under very specific circumstancesHence, we do not have the land littered with fossils of prehistoric dinosaurs, mammoths and sharks.
From bones to fossils
Generally, when a living being dies, breaks down quicklyespecially if it is out in the open. Therefore, the first requirement that must be met for bones or any hard part of the body to become a fossil is that it be buried quickly.
It can happen for any reason, as long as sediment is deposited of ground on them, although it is more likely to occur when they fall to the bed of a river or the sea, for example. In this way, it will be easier for the passage of oxygen to be blocked, which facilitates its decomposition. Even so, the soft parts will gradually decompose. But, in the meantime, the minerals from the sediments are seeping into the holes that remain. In this way, the bones, shells, shells, or even the stems or seeds of a plant they act as a mold for the final form of the fossil.
On the other hand, the more mineral that infiltrates, the more the incipient fossil weighs. This causes it to sink deeper, so that the mud and sand are compressed and the water laden with more minerals that seeps through the ground is squeezed out. Thus, there is a kind of crystallization by which the bones, or whatever structure, they end up turning into rock.
And it is not a process that happens overnight. In fact, by consensus for this type of remains to be considered fossils they must have at least 10,000 years old.
Not everything is dinosaurs
Jurassic Park it did enough for us to associate fossils with dinosaurs as children. However, these are not the only living things whose remains can be fossilized.
They don’t have to be that big to begin with. There are much smaller ones. So much so that a microscope must be used to see them. They are known as microfossils. It is common, for example, the case of pollen or some bacteria. In fact, the oldest fossil that has been found so far is a microfossil. Has some 635 million years and, although it is not clear what its classification would be, it is quite similar to a mushroom.
As for macro-fossils, they come in a wide variety of sizes and origins. Yes there are dinosaurs, but also animals of many sizes, some already extinct and others of species that still walk on Earth. Some are marine, although they are found in terrestrial ecosystems. We must not forget that in the past many now dry lands were flooded by rivers or even oceans. And not all are animals, of course. There are also non-microscopic fungi or plants, for example. Among the latter, in addition, we can even find trees. Good example of it is a 330 million year old specimen that was unearthed from a depth of 56 meters in 1873 and today it is erected in the gardens of the Natural History Museum, London.
Also footprints
Fossils are not always the remains of the structure of what was in the past a living organism.
They can also be remnants of your exercise. They are what is known as traces and can be represented, for example, by tracks or feces of an animal. Even burrows can fossilize if the holes are filled with mineral from the sediments that buries them.
This is also very useful, as it not only helps to know what some extinct animals were like. It also gives information about the way they behaved. Therefore, they are not “just” rocks. Are rocks, with all the splendor and fascination that can come from the word.