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Principle of superposition

From CreationWiki, the encyclopedia of creation science

The principle of superposition, now known as the scientific law of superposition, is an axiom that forms one of the bases of the sciences of geology, archaeology, and other fields dealing with stratigraphy. It was first put forth in the 17th century by the Danish scientist Nicolas Steno.

1 The Process of Superposition
- 1.1 Assumptions and problems
2 References
3 See Also

The Process of Superposition

In its plainest form, it states that layers of rock (strata) are arranged in a time sequence, provided that they have been unaltered since their formation. In other words, each layer or stratum is younger than the one beneath it and older than the one above it, so that the youngest stratum will be at the top of the sequence and the oldest at the bottom. This interpretation follows from the basic logic that a layer of sediment cannot accumulate unless there is already a substrate on which it can collect, and when the lower stratum forms, none of the strata above it existed. The principle is derived in part, from the Principle of Original Horizontality.

Assumptions and problems

The main problem with the principle of superposition is that it takes into account only one particular case of sedimentation. That is the case of an absence of current. In such cases the strata form vertically, that is bottom to top, implying succession of time on a global scale in accordance with the vertical sequence of strata.

Superposition ignores the general case of sedimentation in moving water and most bodies of water have moving water. In moving water, sediment layers form horizontally. The process of sedimentation in moving water has been demonstrated in laboratory experiment. In these examples, thin layers of sediment built horizontally at a noticeable rate with these layers forming one on top of the other as the edge moved forward. There were other layers beneath them but the two on top were easier to watch. In fact it can be shown that Superposition goes against both experiments and observations in sedimentology.