Fossils

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Half-line

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Physics. the time required for one half the atoms of a given amount of a radioactive substance to disintegrate.

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Radioactive decay

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Radioactive decay is the spontaneous breakdown of an atomic nucleus resulting in the release of energy and matter from the nucleus. Remember that a radioisotope has unstable nuclei that does not have enough binding energy to hold the nucleus together.

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Isotope

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any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weights.

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Absolute age

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(geology)

The geologic age of a fossil, or a geologic event or structure expressed in units of time, usually years. Also known as actual age.

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Relative age

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(geology)

The geologic age of a fossil organism, rock, or geologic feature or event defined relative to other organisms, rocks, or features or events rather than in terms of years.

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Trace fossil

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a fossilized track, trail, burrow, boring, or other structure in sedimentary rock that records the presence or behavior of the organism that made it.

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Mold

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he shape created or imparted to a thing

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Cast

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to form (metal, plaster, etc.) into a particular shape by pouring it into a mold in a fluid state and letting it harden.

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Fossil

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any remains, impression, or trace of a living thing of a former geologic age, as a skeleton, footprint, etc.

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Petrified fossil

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organic remains have been replaced by minerals in the slow process of being replaced with stone

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Index fossil

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a widely distributed fossil, of narrow range in time, regarded as characteristic of a given geological formation, used especially in determining the age of related formations.

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Coprolite

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a scientific name for the fossilized excrement, feces or droppings of ancient animals

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Carbon film

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thin film coatings which consist predominantly of the chemical element carbon

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Principle of superposition

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to interpret the relative ages of the layers. This principle states that in a sequence of undisturbed sedimentary layers or lava flows, the oldest layers are at the bottom.