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24 week asses.
chap. 8, 9, 29, 30
| Geologists estimate that the earth is _______ years old | 4.6 billion |
| the principle that geologic processes that occurred in the past can be explained by current geologic processes is called | uniformitarianism |
| layers of rock called _____ show the sequence of events that took place in the past | strata |
| even though all three classes of rock can form layers the ones most commonly studied are | sedimentary rock |
| the boundary between two beds of rock is called a | bedding plane |
| the principle that a sedimentary rock layer is older than the one above it is called the law of | super position |
| the principle that a fault or intrusion is younger than the layers it cuts through is called the law of | cross cutting |
| the absolute age of a rock layer is its _____ age | numeric |
| using the rate of _______ to determine absolute age would be less accurate for a surface feature such as the grand canyon which is millions of years old | erosion |
| in general about 30 cm of sedimentary rock are _______ over a period of 1,000 years | deposited |
| some sedimentary rock layers show annual layers called | varves |
| which layer (summer or winter) is composed of darker finer grains | winter |
| atoms of the same element that have different numbers of neutrons are calles | isotopes |
| the original radioactive isotope is called the ______ isotope | parent |
| the half-life is the time required for half of a radioactive sample to break down by decay to form the ______ isotope | daughter |
| what is the half-life of Uranium-238 | 4.5 billion years |
| the ages of wood, bones, shells, and other f=organic remains embedded in rock can be determined through _______ dating | carbon 14 |
| the scientific study of fossils is called | paleontology |
| some insects become fossilized in hardened tree sap called | amber |
| organisms buried in ____ do bot decay, because bacteria do not survive such low temps. | frozen soil or ice |
| when minerals in groundwater percolate through buried organic matter the result is a nearly perfect mineral replica of the object, this process is called ______. ( hint: it often happens to wood.) | petrificzation |
| a fossil residue of a leaf that makes a "shadow" on sedimentary rock is called a _______ | carbon films |
| fossilized dung or waste is from an animal is called a ______ | coprolites |
| the stones from the digestive tracts of dinosaurs are called | gastrolites |
| fossilized tracks borings or burrows are called _____ fossils | trace |
| fossils that occur only in rock layers of a particular geologic arge are | index |
| geologists also use these fossils to locate deposits of _____ | natural |
| the geolgic rime scale is a | scale that decides earths history into time intervals |
| scientists are able to determine the absolute ages of most rock layers in a geologic | radiometric dating |
| to determine the age of a specific rock, scientists might correlate it with a layer in a geologic column that had the same relative position and | fossil content |
| geologic periods can be divided into | epochs |
| Precambrian time ended about | 542 million years ago |
| what does the law of superposition state? | the principle that a sedimentary rock layer is older than the layers above it and the layers below it if the layers are not distributed |
| what does the law of cross cutting relationships state | the principle that a fault or body of rock is younger than any other body of rock that it cuts through |
| what is radiometric dating | the method of determining the absolute age of an object by comparing the relative percentage of a radio active isotope and a stable isotope |
| what is a parent isotope | original isotope |
| what is a daughter isotope | newly formed isotope |
| what is carbon 14 dating used for | younger rock layers dated intirectly by dating organic material found within the rock. the ages of wood, bones, shells, and other organic remains that are included in the layers and are less than 70,000 years old |
| What is an index fossil | fossil that is used to establish the age of rock layers because it is distinct, abundant, and widespread and existed for only a short span of geologic time |
| why are there few fossils found in Precambrian rocks | because Precambrian life forms lacked bones, shells, or other hard parts that commonly formed fossils |
| what was the major cause of the Permian extinction | drying out of the seas |
| What is ht major cause of ht e cretaceous extinction | asteroid crashed into earth |
| what marks the boundary between the Pleistocene and the Holocene epochs | modern humans |
| what causes aurroras | a spectacular effect of the interaction between the solar wind and earths magnetosphere in the appearance in the sky of bands of light |
| what causes a geomagnetic storm | gusts of particles strike earths magnetosphere or the space around earth that contains a magnetic field, the particles can generate a sudden disturbance in earths magnetic field |
| how does nuclear fusion create energy in the suns coere | process of nuclear fusion; process of combining nuclei of small atoms to form more massive nuclei. |
| what is the average length of the sunspot cysle | 11 years |
| what is the scientifically accepted age of the universe | 4.6 billion years old |
| explain the big bang | the theory that all matter and energy in the universe was compressed into an extreamly small volume that 13 to 15 billion years ago exploded and began expanding in all directions |
| what is the cosmic background radiation | radiation uniformly detected from every direction in space considering a remnant of the big bang |
| what galaxy do we live in | milkyway |
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giannamegna10
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