how are fossils usually formed?

Answer 1

There are several types of fossils, but the commonest is where the soft tissues are replaced with minerals, which become rock-hard. The cavity that the body makes after entombment functions as the mold in which the "fossil" is actually made. Mineral deposition is usually by water perfusion through rock, either by porosity or cracks.

Answer 2

Fossil Formation

Fossils are formed in many different manners. This has lead to much speculation in the past as to how they are formed. At this present time we know much more about the workings of nature and what is feasible and what is not. Many of the theories of formation will be shown below. Some views and hypothesis surrounding them will also be given.

Theory 1: An animal/plant dies in a stream bed and is buried over time.

A few die hard believers of this remain but evidence suggests that this isn't feasible. Typically, most animals don't die in a stream bed. If they do, wave action and predators would destroy most of the carcass leaving nothing to fossilize. The only feasible alternative is that the carcass was washed to a delta in a stream during a flood and buried.

Theory 2: An animal/plant is rapidly buried during a flood/mudslide.

This has been proven to be a very feasible and common method of fossilization. The carcass is protected from scavengers and the interference of other elements.

Theory 3: An animal/plant dies on land and is gradually buried by a build up of soil/sand/decaying plant matter.

Although this was a once common theory, it also has fallen into the perspective of highly unlikely. If an animal dies any where on land, scavengers quickly decimate the remains. The greater the number of predators in a biome, the sooner the destruction of the carcass. Some predators, with excellent smelling ability, actually dig up dead animals to consume them. So the likelihood of this actually occurring is rather slim.

Theory 4: An animal/plant is buried in a volcanic eruption.

This is another widely agreed upon fact. Once again it exhibits two key points that support fossilization (protection from predation and protection from the elements).

Theory 5: An animal/plant dies after being trapped in a tar pit.

If we visit Los Angeles, we would find a place that clearly proves this to be true. Although an animal/plant isn't buried rapidly, as mentioned in previous examples, it does get buried in perhaps days or weeks. A key element again is protection from predators, which are often trapped and contribute to the collection. And another is protection from the elements. Since there is little to affect the trapped specimens at this location after burial, this doesn't appear to be an issue.

Theory 6: An animal/plant dies after falling into a sinkhole.

This theory is widely accepted as being true. If we visit the sinkholes found in Florida, there is enough evidence to support this theory. Since the carcass isn't buried rapidly, it's protection from predators and the elements is key. The key predators of a sinkhole are quite unlikely to be able to consume a large skeleton (i.e. crustations, fish), although a random alligator may remove some parts. And since wave action in conjunction with an abrasive aren't present, there is little elemental destruction.

Theory 7: An animal/plant dies in the sea and is buried by the sand.

Like several theories mentioned before, this one isn't feasible. We know that the seas are full of predators of every shape and form. If a skeleton would survive (which is extremely unlikely unless the animal was massive, i.e. a whale) wave action combined with the sand would eventually wear the bone down to pebbles.

Theory 8: An animal is killed by a higher predator and its remains are preserved.

Skeletons are quite often found in caves. This is typically evidence from human predation. Since people have occasionally used animal parts (skulss, etc.) as ornamentation, they naturally are found where people once lived. The fact that people also protected these sanctuaries of fossildom, kept other predators from accessing them until there was nothing left to attract their attention. And since caves are typically protected from the elements, the fossils survived.

Theory 9: An animal/plant dies and is preserved in ice or peat.

Animals/plants are occasionally found in these situations. For an animal to be buried in ice, it was probably done rapidly. This would fulfill the predator/elements requirements for a fossil. And since some are found with skin, hair, stomach contents, etc. intact, it is much more likely that this was a very rapid event since otherwise the carcass would've decomposed due to natural causes. Concerning peat, carcasses (although dehydrated) have been found containing skin and internal organs. The reason for their preservation is unclear, but a lack of predators would be a clear necessity. Along with this fact that the typical latitude they're found at and their environment may help prevent elemental erosion.

Answer 3

Hi. By being preserved in sediment which then gets converted to rock.

Answer 4

Fosils are formed from a dying creature. They die they rot their bones.

Answer 5

Fossils (from Latin fossus, literally "having been dug up") are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. The totality of fossils and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils across geological time, how they were formed, and the evolutionary relationships between taxa (phylogeny) are some of the most important functions of the science of paleontology.

While most fossils are several thousands to several billions of years old, there is no minimum age for a fossil. Fossils vary in size from microscopic, such as single cells, to gigantic, such as dinosaurs. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous exoskeletons of invertebrates. Preservation of soft tissues is exquisitely rare in the fossil record. Fossils may also consist of the marks left behind by the organism while it was alive, such as the footprint or feces of a reptile. These types of fossil are called trace fossils (or ichnofossils) as opposed to body fossils. Finally, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals; these are known as chemical fossils or biomarkers.

Earliest fossiliferous sites
Earth’s oldest fossils are the stromatolites consisting of rock built from layer upon layer of sediment and precipitants.[1] Based on studies of now-rare (but living) stromatolites (specifically, certain blue-green bacteria), the growth of fossil stromatolitic structures was biogenetically mediated by mats of microorganisms through their entrapment of sediments. However, abiotic mechanisms for stromatolitic growth are also known, leading to a decades-long and sometimes-contentious scientific debate regarding biogenesis of certain formations, especially those from the lower to middle Archaean eon.

It is more widely accepted that stromatolites from the late Archaean and through the middle Proterozoic eon were mostly formed by massive colonies of cyanobacteria (formerly known as blue-green "algae"), and that the oxygen byproduct of their photosynthetic metabolism first resulted in earth’s massive banded iron formations and subsequently oxygenated earth’s atmosphere.

Though rare, microstructures resembling cells are sometimes found within stromatolites; but these are also the source of scientific contention. The Gunflint Chert contains abundant microfossils widely accepted as a diverse consortium of 2.0 bya microbes.[2]

In contrast, putative fossil cyanobacteria cells from the 3.4 bya Warrawoona Group in Western Australia are in dispute since abiotic processes cannot be ruled out.[3] Confirmation of the Warrawoona microstructures as cyanobacteria would profoundly impact our understanding of when and how early life diversified, pushing important evolutionary milestones further back in time (reference). The continued study of these oldest fossils is paramount to calibrate complementary molecular phylogenetics models.

Developments in interpretation of the fossil record
Ever since recorded history began, and probably before, people have found fossils, pieces of rock and minerals which have replaced the remains of biologic organisms or preserved their external form. These fossils, and the totality of their occurrence within the sequence of Earth's rock strata is referred to as the fossil record.

The fossil record was one of the early sources of data relevant to the study of evolution and continues to be relevant to the history of life on Earth. Paleontologists examine the fossil record in order to understand the process of evolution and the way particular species have evolved. Various explanations have been put forth throughout history to explain what fossils are and how they came to be where they were found. Many of these explanations relied on folktales or mythologies. In China the fossil bones of ancient mammals including Homo erectus were often mistaken for “dragon bones” and used as medicine and aphrodisiacs. In the West the presence of fossilized sea creatures high up on mountainsides was proof of the biblical deluge. More scientific views of fossils began to emerge during the Renaissance.

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Answer 6

it takes millions of years.
it is a natural process.