1) Superposition 2) The formation of new rock layes on top of older ones. This allows us to determine the relative age of rocks and fossils. 3) Cross cutting 4) If an igneous intrusion or a fault cuts through existing rock (rock already there), the intrusion/fault is younger than the rock it cuts through. 5) Uniformitarianism 6) The way we observe rocks forming and changing today is the same way that rocks have formed and changed in the past. 7) Horizontality 8) Sedimentary rock layers are deposited horizontally. 9) Correlation 10) Rock layers in different places can be correlated or matched up by matching up the rocks and fossils in the layers. 11) Unconformities 12) An unconformity is found where rock has been eroded, so there is a "missing section of time" in the rock record. An unconformity is younger than any rocks that are below, and older than any rocks that are above.An unconformity is younger than any rocks that are below, and older than any rocks that are above.

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