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Understanding rock relationships is a critical step in understanding the earthquake potential of a region. This animation has both stratification and structure. Stratigraphy is the branch of geology that studies rock layers; structure includes the faults and folds that result from regional & local forces acting on the area.
In this animation, no strata are overturned, thus the following laws apply: The law of superposition simply says that for non-deformed geologic strata, “sedimentary layers are deposited in a time sequence, with the oldest on the bottom and the youngest on the top”. The principle of original horizontality states that rock layers form in the horizontal position, and any deviations from this horizontal position are due to the rocks being disturbed later (the exception being layers deposited on a slope or thick viscous lava flows). The crosscutting law states that if a rock is cut by another rock, then it is older than the rock which has cut it.

 Quicktime (9.25 MB)


Animations and videos are made in partnership with Earthscope, USGS, and Volcano Video & Graphics.

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