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Geologic Time
Earth History
| Question | Answer |
|---|---|
| Absolute Age | a more specific age for a rock, mineral, or other object; done with carbon |
| Cast | a fossil that is a solid copy of an organism's shape |
| Cenozoic Era | a.k.a "Age of Mammals" era that began about 66 million years ago and is the time in Earth's we live in now; |
| Continental Drift Theory | gradual shifting of Earth's plates causing continents to change their global positions over time (Pangea) |
| Deposition | process in which sediment is laid down in new locations |
| Era | a unit of geologic time that includes two or more periods; we have 3 of them; divided by mass extinctions |
| Erosion | the process by which water, ice, wind, or gravity moves weathered rock or soil |
| Evolution | the change in population of a species over time |
| Extinct | describes organisms that no longer exist anywhere on Earth; Happens because species cannot adapt to environmental changes |
| Extrusion | an igneous rock layer formed when lava flows on surface layers of rock and hardens |
| Fault | a break in the Earth's crust |
| Fossil | evidence of past life preserved in rock |
| Fossil record | the complete body of fossils that shows how species and ecosystems change over time |
| Geologic Time Scale | a record of all biological and geological evolution (changes over time) |
| Half-life | the time needed for half of a sample of radioactive substance to undergo radioactive decay |
| Index fossil | a fossil found in a narrow time range but widely distributed around the earth; used to date rock layers |
| Isotope | an atom that has the same number of protons as other atoms of the same element do BUT has a different number of neutrons |
| Intrusion | an igneous rock layer when magma hardens below the Earth's surface |
| Law of Superposition | says that the oldest rocks lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks. |
| Mass extinction | occurs when a large amount of the living things go extinct in a relatively short period of time. |
| Mesozoic Era | a.k.a. "Age of the Reptiles or Dinosaurs" era that began 245 million years ago |
| Mold | a fossil that is formed when an organism is buried in sediment |
| Paleontologist | a scientist that studies fossils to learn about organisms that lived long ago |
| Paleozoic Era | a.k.a. "Age of the Fishes" time in history when organisms with spines appeared (vertebrates: fish, insects, and small reptiles) era that began about 544 million years ago and lasted for almost 300 million years |
| Period | a subdivision of the eras in geologic time; divided by different rock types |
| Precambrian Time | covers about 88% of the Earth's history, bacteria came first and soft multicellular organisms arrived toward the end |
| Radioactive dating | the process by which the age of a rock is determined by measuring the amount of radioactive isotopes present in the rock or rock sample |
| Radioactive decay | when elements break down over time and release particles and energy |
| Relative age | the age of an object compared to the ages of rock layers or fossils near it; used w/ Law of Superposition; an estimation of age |
| Trace fossil | a fossilized mark that is formed in soft sediment by the movement or actions of an animal (ex. footprint) |
| Trilobite | an index fossil that looks like a cockroach |
| Unconformity | a gap in the geologic record; usually caused by erosion, flood, earthquake or other natural causes |
| Petrified fossil | a type of fossil where minerals replace all or part of the organism |
| Preserved remains | remains that are preserved because organisms become trapped in amber, tar, snow |
| Carbon film | an extremely thin coating of carbon on the rock in the shape of a past organism |
| Carbon-14 dating | All plants and animals contain some amount of carbon-14. As long as the organism is alive, the amount of carbon-14 stays the same. After an organism dies, then no more carbon is added and the carbon-14 in the organism's body starts radioactive decay. |
| Igneous rock | rock that forms when magma cools and solidifies |
| Metamorphic rock | rock that has been changed by heat and pressure |
| Sedimentary rock | a rock that forms from compressed or cemented layers of sediment |
| Law of Horizontality | states that sediments settle down in horizontal layers |
| Law of Uniformitarianism | the idea that the same processes we see occurring now also occurred in the past |
| ice core | A long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates. |
Created by:
jhandy8
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