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