Chapter 10 - Fossils
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magnificat on January 24, 2012
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26 terms
Terms | Definitions |
|---|---|
 How does a fossil form? | A fossil forms when living things die and are buried under sediment. |
| Mold | A Mold is a hollow area in sediment in the shape of an organism or part of an organism. |
| Cast | A Cast is a solid copy of the shape of an organism. A cast is the opposite of its mold. |
| Petrified Fossils | Petrified Fossils are fossils in which minerals replace all or part of an organism. |
| Carbon Films | Carbon Films are an extremely thin coating of carbon on rock released by a dead organism. |
| Trace Fossils | Trace Fossils provide evidence of the activities of ancient organisms. Ex. A Fossilized Footprint |
| Law of Superposition | In horizontal sedimentary rock layers the oldest layer is at the bottom. Each higher layer is younger than the layers below it. |
| Extrusion | Lava that hardens on the surface. |
| Intrusion | When magma cools and hardens into a mass of igneous rock. |
| Unconformity | The surface where new rock layers meet a much older rock surface beneath them. |
| Index Fossils | Fossils that help geologists match rock layers |
| Radioactive Decay | Over time elements break down, or decay, by releasing particles and energy in a process called radioactive decay. |
| Half-Life | The half-life of a radioactive element is the time it takes for half of the radioactive atoms to decay. |
| Potassium-Argon Dating | Scientists often date rocks using potassium-40. This form of potassium decays to stable argon-40 and has a half-life of 1.3 billion years. |
| Carbon-14 Dating | Scientists measure the amount of Carbon-14 that is left in the organism's remains. From this amount, they can determine its absolute age. |
| Radioactive Dating | In Radioactive Dating, scientists determine the amount of a radioactive element in a rock |
| Geologic Time Scale | A record of the life forms and geologic events in Earth's history. |
| When do scientists believe Earth was formed? | Earth formed at the same time as the other planets and the sun, roughly 4.6 billion years ago. |
| How did Earth Form? | Scientists think that Earth began as a ball of dust, rock, and ice in space. Gravity pulled this mass together. |
| The Atmosphere | The atmosphere is made up mostly of carbon dioxide, water vapor, and nitrogen. |
| The Oceans | When Earth was formed it was very hot, so all the water evaporated into vapor. after the surface cooled down the vapor fell as rain. |
| The Continents | Earth's rock cooled and hardened and was moved over millions of years as a result of Continental Drift. |
| When were the first living organisms made? | Scientists have found fossils of single-celled organisms in rocks that formed about 3.5 billion years ago. |
| Paleozoic Era | At the beginning of the Paleozoic Era, a great number of different kinds of organisms evolved. |
| The Mesozoic Era | Reptiles were very successful during this era, about 225 million years ago. |
| The Cenozoic Era | The extinction of dinosaurs created an opportunity for mammals to live and evolve on land. |
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