How Are Fossils Formed?

How are fossils formed? For fossil formation to takegive the rock a reddish color. Phosphates may darken
place a series of fortunate events must occur. If anythe rock to gray or black. The possibilities are truly
part of the series is missing, we will never see theendless.
fossil! In fact, fossilization is a rare occurrence. NaturePermineralization
tends toward recycling. That includes just aboutAs the sediments continue to pile on, the lower layers
everything from plants and animals to rocks andbecome compacted by the weight of the layers on
minerals.top. Over time, this pressure turns the sediments into
Let?s narrow it down to just animals for a minute.rock. If mineral-rich water percolates down through the
Animals, dead or alive, are food for other animals.sediments, the fossilization process has an even better
From insects to dinosaurs, an animal could bechance of preserving our ancient animal. Some of the
someone?s lunch! Any part of the animal?s body thatminerals stick to the particles of sediment, effectively
isn?t consumed is usually scattered about; leftovers!gluing them together into a solid mass. These minerals
Just like those leftovers in your fridge, these leftoversmake an impact on our original trilobite as well. Over
make great food for bacteria. In addition, thesethe course of millions of years, they dissolve away the
leftovers are exposed to the elements: sun, rain, andouter shell, sometimes replacing the molecules of
even the soil itself all help to breakdown andexoskeleton with molecules of calcite or other minerals.
decompose the sturdiest of bones, shells and wood.In time, the entire shell is replaced leaving rock in the
If we are ever going to see a fossil, some veryexact shape of the trilobite.
specialized events must intervene to ward off theUplift
natural process of decomposition. The following is theAs the continental plates move around the earth,
most common scenario for fossil formation:crashing into each other, mountains are formed.
How Are Fossils Formed? Death Is The First StepFormer sea floors are lifted up and become dry land.
To start with, an animal or plant must die in water orThis is exactly what has happened to our trilobite. Now
near enough to fall in shortly after death. The watera fully formed fossil, our trilobite is buried under
insulates the remains from many of the elements thathundreds or even thousands of feet of rock! Thanks
contribute to decomposition. An example may beto the movement of the plates, our trilobite will come
helpful. Let?s say that a trilobite has died of old age oncloser to the surface and nearer to discovery by
the bottom of the sea. Bacteria consume the softsome fortunate fossil hunter. Luckily, nothing stays the
body parts but leave the hard exoskeleton intact.same.
How are fossils formed? Step two is SedimentationErosion at work
As time passes, sediments bury the exoskeleton. TheRain, wind, earthquakes, freeze and thaw all work
faster this happens the more likely fossilization willtoward erosion. The mountains that were built up are
occur. Land and mudslides definitely help. River deltasworn away over time. Our fossil trilobite once again
are also good for quick accumulation of sediments.sees the light of day! With a little wisdom about where
This further insulates our trilobite from decomposition.to look and some luck, you may be the first one to find
The sediments themselves have a huge influence onhim!
how well our trilobite fossil turns out. Very fine-grainedThis is the fossilization process known as
particles, like clays, allow more detail in the future fossil.Permineralization. It is not the only answer to the
Course sediments, like sand, allow less detail to show.question: "How Are Fossils Formed?" There are many
The chemical make up of the sediments alsoother ways that fossils can be formed. You can read
contributes to the future fossil. If iron is present, it mayabout them using the links below.