Uniformitarianism <ul><li>The concept that processes that have shaped Earth in the past are essentially the same as those operating today </li></ul>
Relative dating <ul><li>Process by which rocks are placed in their proper sequence or order; Only the chronological order of events is determined, not the absolute age in years. </li></ul>
unconformity <ul><li>A surface that represents a break in the rock record, caused by erosion or lack of deposition </li></ul>
Correlation <ul><li>Establishing the equivalence of rocks of similar age in different areas </li></ul>
Key Concept <ul><li>Rocks record geological events and changing life forms of the past </li></ul>
Key concept <ul><li>We have learned that earth is much older than anyone had previously imagined and that its surface and interior have been changed by the same geological processes that continue today </li></ul>
Key concept <ul><li>Uniformitarianism means that the forces and processes that we observe today have been at work for a very long time </li></ul>
Key Concept <ul><li>Relative dating tells us the sequence in which events occurred, not how long ago they occurred </li></ul>
Key Concept <ul><li>The law of superposition states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it. </li></ul>
Key Concept <ul><li>The principle of original horizontality means that layers of sediment are generally deposited in a horizontal position. </li></ul>
Key concept <ul><li>An unconformity represents a long period during which deposition stopped, erosion removed previously formed rocks, and then deposition resumed. </li></ul>
Key Concept <ul><li>An angular unconformity indicates that during the pause in deposition, a period of deformation (folding or tilting) and erosion occurred. </li></ul>
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