earth's history
earth science
Terms
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- decay
- the organic phenomenon of rotting
- folds
- a bend in rock that forms where part of Earth's crust is compressed
- orogeny
- the process of mountain formation (especially by the upward displacement of the earth's crust)
- radioactive isotope
- the nucleus decays, giving off particles and energy. Can harm living organisms by damaging cellular molecules
- radioactive decay
- the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation
- relative age
- the age of rock compared to the ages of other rocks
- faults
- fracturing of rock followed by the movement of two sides of the fracture relative to one another
- radioactive dating
- a dating method based on the rate of disintegration of radioactive isotopes, used to determine the age of rocks and fossils
- joints
- cracks along numerous flat surfaces that show no displacement and are parallel to one another
- contact metamorphism
- heated by adjacent rising lava
- era
- a major division of geological time
- index fossil
- a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found
- epoch
- a unit of geological time
- half-life
- Period of time which splits dating in half by measuring carbon 14 levels
- principle of superposition
- in any undisturbed sequence of sediment or sedimentary rocks, the age becomes progressively younger from bottom to top
- unconformity
- A surface that represents a break in the rock record, caused by erosion or lack of deposition
- absolute age
- The age of a rock given as the number of years since the rock formed.
- correlation
- a statistical relation between two or more variables such that systematic changes in the value of one variable are accompanied by systematic changes in the other
- fossil
- the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil
- period
- an amount of time
- volcanic ash
- Somewhat larger volcanic debris, up to 5 millimeters in diameter, which is shot into the atmosphere during an eruption.
- eon
- the longest division of geological time
- cracks
- A fissure in rock which may eventually become a fault.
- geologic time
- the time of the physical formation and development of the earth (especially prior to human history)