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Chapter 8 Assessment
8th grade Earth Science
Question | Answer |
---|---|
How old is the Earth according to geologists. | 4.6 billion years old. |
The principal that geologic processes that occurred in the past can be explained by current geologic processes. | Uniformitarianism. |
The layers of rock that show the sequence of events that took place in the past. | Strata. |
The most commonly studied of the three classes of rock layers. | Sedimentary rock. |
The boundary between two beds of rock. | Bedding plane. |
The principal that a sedimentary rock layer is older than the one above it. | The law of superposition. |
The principal that a fault or intrusion is younger than the layers it cuts through. | The law of crosscutting relationships. |
The absolute age of a rock layer is its... | Numeric age. |
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. |
The layer that is composed of darker, finer grains. | Winter layer. |
Atoms of the same element that have different numbers of neutrons are called _____. | Isotopes. |
The original radioactive isotope. | The parent isotope. |
The half-life is the time required for half of a radioactive sample to break down by decay to form the _____ ______. | Daughter isotope. |
What is the half-life of Uranium-238 | 4.5 billion years. |
The ages of wood, bones, shells, and other organic remains embedded in rock can be determined through ____ _____. | Carbon dating. |
The scientific study fossils. | Paleontology. |
Some insects become fossilized in hardened tree sap called _____. | Amber. |
Organisms buried in _____ don't decay because bacteria don't survive low temperatures. | 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 ________. | Petrification. |
A fossil residue of a leaf that makes a "shadow" on sedimentary rock is called a ______. | Carbon film. |
Fossilized dung or waste is from an animal is called _____. | Coprolites. |
The stones from the digestive tracts of dinosaurs are called ____. | Gastroliths |
Fossilized tracks, borings, or burrows are called ____ ____. | Trace fossils. |
Fossils that occur only in rock layers of a particular geologic age are called _____ ______. | Index fossils. |
Geologists also use these fossils to locate deposits of _____ ___ _____ ______. | Oil and natural gas. |