What is the Law of Superposition?

The law states that in an undisturbed sequence, younger rocks are found below older ones. The position of an object tells you its age. This article will show you how to date objects by applying this law and become a master archaeologist!

archaeologist, archeology, excavation @ Pixabay

To determine the relative order of deposition for stratified deposits. Find the finest-grained material first and then work up towards progressively coarser materials until you reach the topmost layer.

For example, let’s say we have three layers with nicely preserved stratification – fine sand at the bottom, followed by laminated siltstone about four inches thick (middle), topped off with coarse sandstone about one foot thick (top). If I were dating these layers, I would date the fine sand layer first, then work my way up to the topmost coarse sandstone.

To determine a more accurate age for an object: use radiometric dating methods. If I were using this method and wanted to find out how old something was, say 100 years ago with no carbon-14 in it whatsoever (no C14), I could go about finding that answer one of two ways – by trying to figure out when it came into existence or when its last decay took place.

To continue our example from before, if we found three layers of stratified deposits and needed to get down closer than four inches on the laminated siltstone layer, taking samples at different intervals will give us better accuracy.


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