sedmintary rock - rock that forms when sediments are deposited in layers, compacted together and cemented in place naturally, radiometric dating - method for getting an exact age from a material using the amounts of radioactive isotopes in it, Radioactive isotopes - Carbon-14, Uranium-238, Uranium-235, half life - the amount of time it takes for half of the original amount of a radioactive isotope to decay, fossil - when a living organism is transformed into stone in sedimentary rocks, Fossils are only found - in sedimentary rocks, index fossil - a unique, short lived fossil that marks a specific geologic time period when it is found, fault - a large fracture in bedrock causing displacement across a rock layer...younger than every rock layer it cuts through , igneous intrusion - igneous material that is injected into bedrock cutting through layers...younger than every layer it cuts through , weathering - when rock/mineral material is broken down by physical or chemical means, physical weatehring - the breaking of rock down into pieces, chemical weathering - breaking down of rock material chemically changing its composition, sediment - weathered broken down rock and mineral materila, superposition - oldest rock layers are deposited first, youngest are deposited last...oldest on bottom, youngest on top, erosion - when weathered rock material is carried away by wind, water or gravity, unconformity - a surface that represents missing geologic time in the rock record due to either erosion or periods of non-deposition, stratigraphic correlation - the matching of rock layers to other rock layers of the same age in order toe determine the geologic history of a region and identify unconformities, types of physical weathering - wedging, abrasion, root wedging, frost action - weathering that occurs when rock materials are broken apart by the expansion of freezing ice, abrasion - weathering that occurs when small particles carried by wind/water chip away at rock materials, root wedging - when growing roots of trees break rocks apart, types of chemical weathering - dissolving, dissolution, oxydation, oxydation - when rock mateirals react with oxygen forming oxides such as rust, dissolfing/dissolution - when rock materials is chemically dissolved by acid or acid rain ,

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