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Relative Dating
| Term | Definition |
|---|---|
| extrusion | an igneous rock layer that forms when lava flows onto Earth's surface and hardens. It is younger than any rock it passes through. |
| intrusion | an igneous rock layer that forms when magma hardens beneath Earth's surface. It is younger than any rock it passes through. |
| fault | a break or crack in rock. It is younger than any rock it passes through. |
| unconformity | formed at a place where an old and eroded rock surface makes contact with a new rock layer. |
| Law of Superposition | each layer is older than the layer above it |
| Law of Original Horizontality | each layer was deposited horizontally originally |
| Law of Lateral Continuity | layers on each side of a valley can be matched up |
| Law of Cross Cutting Relationships | a fault or other body of rock cuts through another body of rock then it must be younger in age than the rock through which it cuts and displaces |