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ES1-Unit 6 Vocab
ES1-Unit 6 Vocabulary: Geological Time
Question | Answer |
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Fossil | remains, imprints, or traces of prehistoric organisms that can tell when and where organisms once lived and how they lived |
Index fossil | remains of species that existed on Earth for a relatively short period of time, where abundant and widespread geography, and can be used by geologists to assign the ages of rock layers |
Principle of superposition | states that in undisturbed rock layers, the oldest rocks are on the bottom and the rocks become progressively younger toward the top |
Law of Horizontality | states that layers will be deposited and eroded horizontally due to gravity. surface of a rock layer will be horizontal at time of formation. |
relative age | the age of something compared with other things |
unconformity | gap in rock layer that is due to erosion, re-crystalization by magma, or periods without any deposition |
absolute age | age, in years, of a rock or other object; can be determined by using properties of the atoms that make up minerals |
radioactive decay | process in which some isotopes break down into other isotopes and particles |
half-life | time it takes for half the atoms of an isotope to decay |
radiometric dating | process used to calculate the absolute age of rock by measuring the ratio of parent isotope to daughter product in a mineral and knowing the half-life of the parent |
geologic time scale | division of Earth's history into time units based largely on the type of life forms that lived only during certain periods |
species | group of organisms that reproduces only with other members of their own group |
natural selection | process by which organisms that are suited to a particular environment are better able to survive and reproduce than organisms that are not |
cyanobacteria | chlorophyll-containing, photosynthetic bacteria thought to be one of Earth's earliest life-forms. Gave rise to Stromatolites. |
Eon | longest subdivision in the geologic time scale that is based onteh abundance of certain types of fossils and is subdivided into eras periods and epochs |
Era | second-longest division of geologic time; is subdivided into periods and is based on major worldwide changes in types of fossils |
Period | third-longest division of geologic time; is subdivided into epochs and is characterized by the types of life that existed worldwide |
Epoch | next smaller division of geologic time after the period; is characterized by differences in life-forms that may vary regionally |
Trilobite | well-known fossil group of extinct marine arthropods. One of the earliest known groups of arthropods (related to lobsters & crabs today), many different variants & can be used as an index fossil |
Pangaea | large, ancient landmass that was composed of all the continents joined together |
Chesapeake Bay Impact Event | Meteorite impact at mouth of what is now the Chesapeake Bay, occurred 35 million years ago |
Continent-continent collision zone | Convergent zone where two continents meet and one subducts. VERY high mountains are formed (ex. Himalayans), earthquakes common during convergence, volcanoes may form but not frequently. How Appalachian mountains were formed. |
Continent-oceanic collision zone | Convergent zone where a continental plate meets an oceanic plate. Mountains are formed (ex. Rockies). Many earthquakes and volcanoes near the convergence. |
Convergent zone | Region where two plates meet. The more dense plate will subduct. (ring of fire in Pacific) |
Divergent zone | Region where two plates pull apart and form a rift. (ex. Mid-Atlantic rift, African Rift Valley) |