The law of superposition in sedimentary rocks is based on the observation that the oldest rocks tend to be closest to the Earth`s surface (i.e. closest to the surface that erosion will reach). A rock can be said to be young if it is made of a smaller, poorly sorted material, and old if it is made of a larger, better-sorted material. In fact, the surface of the floor consists of the surface of the younger material, which is covered with layers of older material. The law of superposition does not mean that all geological features can be explained by superposition alone. For example, the folding of layers in a mountain range is often explained by the law of convolution. Similarly, when looking at oil shale layers, there is a maximum age law, which can be explained by the fact that the last rock exposed is the oldest age. In general, however, many geological structures are more naturally explained by a combination of the laws of superposition and the law of sedimentary basin development, and not just by the law of superposition. One of the limitations of the principle of superposition geology is that it cannot be applied because it can be applied to certain neighboring areas such as archaeology. Stratigraphic superposition in archaeology differs from the law of stratigraphy in geology. Indeed, the processes involved in the deposit of archaeological layers differ from the geological processes that lead to structural stratification, which is necessary to explain the law of superposition.
The law of superposition explains why streams follow certain paths through surfaces such as rivers, where the layers are often more or less vertical. Horizontally separated water tends to be altered into shallow horizontal layers that can even be completely horizontal. However, the layers of a valley are younger than the upper layers, and as a result, the valley bed falls downwards when altered. In geology, the law of superposition states that the sequence of layers observed in sedimentary rocks marks the moment of deposition of layers. The lowest layer is the oldest deposition layer and the overlying layers are younger successive deposition layers according to the law of definition of superposition. Therefore, the principle of superposition geology is one of the important concepts to explain geological stratigraphy, which is widely used in the fields of geology, archaeology and other related fields. In a very simple way, the law of superposition states that if there is geological stratification, the first layers deposited or formed will be the oldest, followed by the younger ones that will form over time due to ever more recent deposits. But the condition for this law to be true is that the layers of the rock must not be deformed due to any of the exogenous processes such as weathering and erosion. This is the most important concept in stratigraphic dating, but it assumes that the law of superposition is true and that the layer formed by deposition cannot be older than the mineral content of the layer/layer. The law of superposition was first established by the Danish scientist Nicolas Steno. It was later propagated into English literature by William Smith, who also used the principle of superposition geology to create the first geological map of Britain.
Stratification behaves differently with magmatic deposits formed on the surface such as lava flows and ash falls, and therefore layering cannot always be successfully applied under certain conditions. In many cases, the law of superposition can be considered the most important basic principle behind a particular feature, rather than the sole explanation. For example, the shape of rivers can be explained by a combination of the law of superposition and the law of development of sedimentary basins. The law of superposition states that in each of the undisturbed rock sequences deposited in layers, the youngest layer will always be at the top and the oldest layer will always be below. The best example of the law of superposition is one of the sedimentary rocks that are not deformed because sedimentary rocks are formed by the deposition of various minerals and rock fragments. The law of superposition is a geological principle used to determine the relative age of rock layers. The law of superposition was first proposed in 1669 by the Danish scientist Nicolas Steno and is included as one of his main theses in the groundbreaking seminal work Dissertationis prodromus (1669). [1] The law of superposition is an axiom that constitutes one of the foundations of the sciences of geology, archaeology and other fields of geological stratigraphy. In its simplest form, it indicates that in undistorted stratigraphic sequences, the oldest layers are at the bottom of the sequence, while new material accumulates on the surface to form new deposits over time.
This is of paramount importance for stratigraphic dating, which requires a number of assumptions, including the fact that the law of superposition applies and that an object cannot be older than the materials it is made of. To illustrate the practical applications of layering in scientific research, sedimentary rocks that have not been deformed by more than 90° will have the oldest layers on the ground, allowing paleontologists and paleobotanists to identify the relative age of all fossils found in the layers, with the remains of the most archaic life forms being limited to the lowest. These results can inform the community about the fossil record covering relevant strata to determine which species coexisted over time and which species existed successively in a potentially evolutionary or phylogenetically relevant way. The law of superposition is one of the principles of geology that scientists use to determine the relative age of rock layers or strata. This principle states that rock layers are superimposed or superimposed. The oldest rock layers will be at the bottom and the youngest at the top. Think of it this way: you have a magazine subscription and receive a magazine in the mail every month. You read the January magazine and put it in a box when you`re done. When you`re done with the February magazine, place it on the January issue. This continues, month after month, until December.
If you now look in the box, you will only see the December issue at the top of the magazine stack. Below are eleven more, in order, with the oldest issue – January – at the bottom and the youngest magazine – December – at the top. The same goes for rock layers. It seems like a simple and even obvious concept, but it was a new idea in 1669. At that time, a Danish naturalist named Nichlaus Steno published his theory that older layers of sedimentary rock are buried deeper into the planet than younger layers deposited horizontally on older layers. This principle, which is fundamental today, became known as the law of superposition and is considered the fundamental law of geology. Using this principle, geologists were able to determine which rock layers were the oldest long before the technology to calculate the absolute age of rocks existed. However, it is important to know that before applying the law of superposition, a geologist must determine how the layers formed.
If the rock layers are the result of sedimentation, you can assume that the layers were deposited from bottom to top. However, if the rock layers are metamorphic, for example, the relative age of the layers can vary greatly because these layers have not evolved by deposition, but by pressure. This means that all these layers of metamorphic rock could have formed simultaneously, so the upper layer may not be younger than the lower layer. It`s also important to know that sedimentary rock layers can also be out of sequence if the layers have been altered – folding, intrusion, and cross-cutting are just a few methods that can alter rock layers. Paleontologists also use the principle of Steno superposition. They dig through layers of sedimentary rock to dig up fossils and are able to arrange them chronologically by noting the layers in which they are found. It also works the other way around: fossils can be a key to determining the relative age of sedimentary rocks. The order in which fossils associated with certain periods appear and disappear in rock layers provides information about the age of these layers. The overlap in archaeology, and in particular in the use of stratification during excavations, is somewhat different, as the processes of deposition of archaeological layers are somewhat different from geological processes.
Human interventions and activities in the archaeological record do not have to be formed chronologically from top to bottom or to be deformed from the horizontal, as are natural layers by equivalent processes. Some archaeological layers (often called contexts or layers) are created by undermining the earlier layers. An example would be that backfilling of sludge from an underground drain would form some time after the ground immediately above. Other examples of non-vertical overlay would be changes to standing structures such as creating new doors and windows in a wall. Overlay in archaeology requires a number of interpretations to correctly identify chronological sequences, and in this sense, overlay in archaeology is more dynamic and multidimensional.