Answer:Law of Superposition
Explanation:
The law states that strata that are younger will be deposited on top of strata that are older, given normal conditions of deposition. This law is the guiding principle of stratigraphy, or the study of geological or soil layers. Stratigraphy is still the single best method that archaeologists have for determining the relative ages of archaeological materials.
Many times the layers of rock have been disturbed. Then other principles come into play.
Gaps in the rock record, due to non-deposition and/or erosion, are called unconformities. Unconformities caused by erosion are commonly represented diagrammatically by an irregular or jagged line.
If the layers are sedimentary or volcanic, then the assumption that the layers formed one after the other, from bottom to top, is justified. But if the layers are made of metamorphic or intrusive igneous rocks, then the age relationships may be quite different.
In metamorphic rocks, layering may develop in response to application of pressure. In that case, the layers may all form at the same time. The position of a layer within the series, above or below another layer, will not be indicative of whether it is younger or older.
When an igneous intrusion crosses several layers of rock, then the igneous intrusion is younger than any of the rocks that it cuts across.
The above also holds true for a fault that cuts across layers.
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