- A fossil is any evidence of past plant or animal life that is preserved in the material of the Earth’s crust, and Paleontology is the branch of biology that studies the forms of life that existed in former geologic periods, primarily by studying fossils.
- The only way scientists can study dinosaurs, prehistoric people and other animals is by the fossils that were left behind. Paleontologist’s estimate that only a small percentage of the dinosaurs that ever lived have been or will be found as fossils, because their bodies simply decayed.
- The word fossil comes from the Latin word fossils, which means, “dug up”.
- Most fossils are excavated from sedimentary rock layers. Sedimentary rock is rock that has formed from materials like sand, mud, and small pieces of rock.
- Over long periods of time, these small pieces of debris are squeezed and are buried under more and more layers of sediment that piles up on top of it. Eventually, they are compressed into sedimentary rock.
- The fossil of a bone doesn’t have any bone in it. A fossilized object has the same shape as the original object, but is chemically more like a rock.
- Some animals were quickly buried after their death by sinking in mud, being buried in a sandstorm or falling into a tar pit. The parts of the animals that didn’t rot, like bones and teeth, were encased in the newly formed sediment.
- When the animals are buried their bodies undergo a chemical change. Water seeps into the minerals in their bodies. The chemicals in the bone are replaced by rock-hard minerals. This process is called permineralization. In the end we get a heavy, rock-like copy of the original object – a fossil. The fossil has the same shape as the original object, but is chemically more like a rock.
- Petrification can preserve hard and soft parts and slowly replaces organic material with pyrite, calcite, or silica, forming a rock-like fossil. Wood is often found petrified. Fossils of imprints may form, like casts of dinosaur footprints. The impressions, in the right circumstances, fill with sediments that fossilize.
- Some organisms are embedded in amber which is the hardened sap from a tree. This usually preserved insects or pieces of plants. The movie “Jurassic Park” takes the dinosaur DNA from the mosquitoes embedded in amber.
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Miller Museum: Dawn of Animal Life
National History Museum – University of Oslo
Paleontological Research Institution
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UC Museum of Paleontology
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Utah Geological Survey: Dinosaurs and Fossils
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