Ees 101 Iii--9Th Column

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Relative Dating

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is the science determining the relative order of past events, without necessarily determining their absolute age.

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Absolute Dating or Numerical Dating

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is the process of determining an approximate computed age in archaeology and geology.
--assigning numeric ages

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Uniformitarianism

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proposed that uniform gradual processes (such as for example the slow erosion of the coast by the impact of waves) shaped the geologic record of the earth over an immensely long period of time. He assumed that the acting processes were the same than those that we see in action at present (rivers, volcanoes, waves, tides etc.).

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Principle of Superposition

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states that a sedimentary rock layer in a tectonically undisturbed sequence is younger than the one beneath it and older than the one above it. Logically a younger layer cannot slip beneath a layer previously deposited. This principle allows sedimentary layers to be viewed as a form of vertical time line, a partial or complete record of the time elapsed from deposition of the lowest layer to deposition of the highest bed.[16]

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Principle of Original Horizontality

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ayers of sediment are originally deposited horizontally under the action of gravity.

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Principle of Original Continuity

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states that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous. As a result, rocks that are otherwise similar, but are now separated by a valley or other erosional feature, can be assumed to be originally continuous.

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Cross-Cutting Relationships

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cross-cutting relationships states that the geologic feature which cuts another is the younger of the two features.

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Inclusions

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if inclusions (or clasts) are found in a formation, then the inclusions must be older than the formation that contains them.

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Baked or Chilled Contacts

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an igneous intrusion bakes surrounding rocks, the rock that has been baked must be older than the intrusion

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Lithostratigraphy

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is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers.

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Correlation

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orrelation refers to the methods by which the age relationship between various strata of Earth's crust is established. Such relationships can be established, in general, in one of two ways: by comparing the physical characteristics of strata with each other (physical correlation); and by comparing the type of fossils found in various strata (fossil correlation).

Correlation is an important geological technique because it provides information with regard to changes that have taken place at various times in Earth history. It also provides clues as to the times at which such changes have occurred. One result of correlational studies has been the development of a geologic time scale that separates Earth history into a number of discrete time blocks known as eras, periods, and epochs.

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The Geologic Time Scale

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eologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth.

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Chronostratigraphic Units

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Chronostratigraphic units, with examples:[1]
eonothem - Phanerozoic
erathem - Paleozoic
system - Ordovician
series - Upper Ordovician
stage - Ashgill

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Geochronologic Units

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Geochronological units are periods of time,

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Biostratigraphy

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Chronostratigraphic units are geological material,where fossils could have been deposited

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Radiometric Dating

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is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.[1] It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and can be used to date a wide range of natural and man-made materials.

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Radioactive Decay

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is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles

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Half-life

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abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half.

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Counting Rings

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Dendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year.

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Sclerochronology

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Sclerochronology is the study of physical and chemical variations in the accretionary hard tissues of invertebrates and coralline red algae, and the temporal context in which they formed.

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Magnetostratigraphy

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is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their characteristic remanent magnetization (ChRM), that is, the polarity of Earth's magnetic field at the time a stratum was deposited. This is possible because volcanic flows acquire a thermoremanent magnetization and sediments acquire a depositional remanent magnetization, both of which reflect the direction of the Earth's field at the time of formation.

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Chemostratigraphy

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is the study of the variation of chemistry within sedimentary sequences. The name of the field is relatively young,