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Geological Evolution
Geological Evolution
27
Science
8th Grade
01/23/2012

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Term
Absolute Age
Definition
The method of measuring the age of an event or object in years. The actual age for a rock or mineral.
Term
Cambrian Boundary
Definition
The first geological period of the Paleozoic Era. Prior to this time, life forms were small and simple. After this time organisms became more common and complex.
Term
Cenozoic Era
Definition
Era that began about 66 million years ago, known as the “Age of Mammals”
Term
Chemical Weathering
Definition
A weathering process whereby rocks and minerals are broken down and transformed into new chemical combinations through chemical reactions.
Term
Continental Drift
Definition
Theory that states that the gradual shifting of Earth’s plates causes continents to change their global positions over time
Term
Convergent Boundary
Definition
The boundary formed by the collision of two lithospheric plates.
Term
Divergent Boundary
Definition
The boundary between two tectonic plates that are moving away from each other.
Term
Eon
Definition
The largest division of geologic time. Earth’s 4.6 billion year history is divided into four eons.
Term
Epoch
Definition
A subdivision of periods in geologic time
Term
Era
Definition
A unit of geologic time that includes two or more periods.
Term
Geologic Time scale
Definition
The standard method used to divide the Earth’s long natural history into manageable parts
Term
Geological Evolution
Definition
The process of the Earth changing over time
Term
Half-life
Definition
The time needed for half of a sample of radioactive substance to undergo radioactive decay.
Term
Ice Cores
Definition
Cylindrical samples of ice removed from ice sheets and glaciers. They are taken from regions that stay frozen year round and they contain detailed information about the history of the Earth.
Term
Igneous Intrusion
Definition
The forcing of molten rock into earlier rock layer formations.
Term
Law of superposition
Definition
States that the oldest rocks lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks
Term
Mechanical Weathering
Definition
The erosion or breakdown of rock into smaller fragments by natural physical agents with no chemicals involved
Term
Mesozoic era
Definition
Era that began 245 million years ago, known as the age of the dinosaurs
Term
Paleozoic era
Definition
Era that began about 544 million years ago and lasted for almost 300 million years
Term
Period
Definition
A subdivision of the eras in geologic time
Term
Plate tectonics
Definition
The theory that explains how large pieces of the Earth’s outermost layer called tectonic plates move and change shape.
Term
Radioactive Dating
Definition
The process by which the age of a rock is determined by measuring the amount of radioactive isotopes present in the rock or rock sample
Term
Radioactive decay
Definition
The process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
Term
Relative dating
Definition
Uses information about rock layers and the fossil record to determine the age relationships between rocks
Term
Trace fossil
Definition
A fossilized mark that is formed in soft sediment by the movement or actions of an animal.
Term
Transform Boundary
Definition
The boundary formed by the tectonic plates sliding horizontally past each other
Term
Unconformity
Definition
Gaps in the rock record.
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