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Fossils Vocab
| Term | Definition |
|---|---|
| Fossil | Preserved remains or traces of animals, plants, and other organism from the remote past Found in sedimentary rock layers Can be as small as bacteria or as giant as a dinosaur Paleontology is the study of fossils. |
| Sedimentary Rocks | Formed in layers by the deposition of weathered rocks Sediments are pressed and cemented together. Fossils are found here because sedimentary rocks form at low temperatures and pressure. Fossils and the rock layer in which they are found are approxima |
| Stromatolites | Rock like structures built by blue-green algae. First forms of life on Earth - oldest known fossils (3.5 b.y.) Still found in some remote areas of the world today |
| Trace Fossil | Provides indirect evidence of life in the past rather than the body of the animal itself. Examples of trace fossils Footprints Tracks Burrows Feces Borings |
| Index Fossil | Special fossils called “index fossils” indicate to the boundaries in geological time. This is a tool to determine the age of rocks. Characteristics of Index Fossils Easily recognizable Abundant Wide geographic distribution Lived a short period of g |
| Casts | Cast – organism dies and the cavity fills with minerals, maybe sand or clay Many times shells are fossilized through these processes. |
| Molds | Mold – organism dies and there is no filling of the cavity with minerals Many times shells are fossilized through these processes. |
| Relative Age | Index fossils are used to correlate the age of the rock strata. If two different rock strata in different areas on Earth contain the same index fossils, then the strata are probably the same age. Also called ‘relative age’ |
| Absolute Age | Most accurate form of dating, also call radiometric dating Uses the decay of radioactive elements to find the absolute age of a rock or fossil This relies on the property of half life, which is the predictable time an element takes to decay. |
| Geologic Time Scale | The Geologic Time Scale is a chronological representation of Earth’s geologic history going back 4.6 billion years until present day. |
| Fossil Record | By using relative and absolute dating scientists are able to put together the Earth’s geologic history. Through fossils scientists can see changes in organisms over time. |
| Permineralization | Groundwater carries dissolved minerals into the pores and cavities of bone, wood, or shells. The original material is preserved rather than replaced. Bones, teeth, and shells can be preserved this way. |
| Petrification | Two types – Replacement and Permineralization Both result in organic material converting into stone or a similar substance Petrified wood is the most well know example of this process. |
| Carbonization | The process by which all substances of plants and animals decay, except carbon. This leaves a carbon film on the sedimentary rock. This process particularly occurs in plants and fish. |
| Law of Superposition | Geologists assume the newest rock layers are on top of the older ones, unless some type of disturbance occurs. This law helps scientists find the age of fossils They can say one fossil is older than another because of the strata in which it was found. |
| Fossil Resin | Resin is from certain plants, which is thought to protect them from insects and seals off plant injuries. The sticky resin captures insects and other invertebrates. It hardens and they are preserved in the resin including their DNA. is known as amber. |
| Tar & Ice | An animal can become trapped in tar and the whole body can be preserved. An example is the La Brea Tart Pits L.A. Freezing can also trap whole animals. Mammoth’s bodies have been found with skin, hair and even organs. |
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