What is the Difference Between Principle of Original Horizontality and Superposition

The main difference between principle of original horizontality and superposition is that principle of horizontality states that layers of sediments in a rock are originally deposited in a horizontal pattern whereas the principle of superposition states that the oldest strata are at the bottom line of the rock.

The principle of original horizontality and superposition are important geological concepts that describe the deposition pattern of a rock. Moreover, there are three major types of rock on planet Earth: igneous rocks, sedimentary rocks, and metamorphic rocks. These geological concepts can, therefore, describe the origin of these rock types based on observations and predictions.

Key Areas Covered

1. What is the Principle of Original Horizontality 
     – Definition, Characteristics, Rock-Formation
2. What is the Principle of Superposition
     – Definition, Characteristics, Rock-Formation
3. What is the Difference Between Principle of Original Horizontality and Superposition
     – Comparison of Key Differences

Key Terms

Principle of Original Horizontality, Principle of Superposition, Rocks

What is the Principle of Original Horizontality

The principle of original horizontality declares that the origin of rock is based on the horizontal deposition. In other words, this principle states that the layers of sediment (rock) are originally deposited in a horizontal pattern, which is governed by the action of gravity. Therefore, we can use this theory as a relative dating technique for rocks. Moreover, we can use this theory mainly for the analysis of folded and tilted strata. In fact, the founder of this principle was the Danish geologist Nicholas Steno.

Figure 1: Horizontal Pattern of Rock Formation via Deposition of Materials

Moreover, observations regarding the principle of original horizontality have led us to believe that the Earth has not been static as great forces have been applied on Earth over a long time period. In addition, this principle helps us to get build theories regarding plate tectonics, movement and collision of plates, etc.

What is the Principle of Superposition

Principle of superposition is a concept in geology that describes the patterns in undeformed stratigraphic sequences. In other words, this principle describes that the oldest strata in an un-deformed stratigraphic sequence occur at the bottom of the sequence. Thus, it is a way of relative dating rocks. Moreover, this theory has applications in geology, archaeology, and other areas that deal with geological stratigraphy. Also, similar to the principle of horizontality, the Danish geologist Nicholas Steno founded this principle too. 

Figure 2: An Un-deformed Sequence of Rock Layers

The above image shows a particular rock in Norway, which is composed of layer upon layer of rock material. Moreover, there is no overturning in this rock, which leads it to have the oldest rock layer at the bottom.

Difference Between Principle of Original Horizontality and Superposition

Definition

The principle of original horizontality states that the origin of rock is based on the horizontal deposition while the principle of superposition is a concept in geology that describes the patterns in undeformed stratigraphic sequences.

Theory

Moreover, the principle of original horizontality states that the layers of sediment (rock) are originally deposited in a horizontal pattern, which is governed by the action of gravity. In contrast, the principle of superposition describes that the oldest strata in an un-deformed stratigraphic sequence occur at the bottom of the sequence.

Cause

In the principle of original horizontally, the action of gravity causes horizontal deposition while in the principle of superposition, un-deformation occurs due to absence of overturning.

Conclusion

In conclusion, the principle of original horizontality and superposition are important geological concepts that describe the deposition pattern of a rock. The main difference between principle of original horizontality and superposition is that principle of original horizontality states that the layers of sediment in a rock are originally deposited in a horizontal pattern whereas the principle of superposition states that the oldest strata are at the bottom line of the rock.

Reference:

1. “Principle of Original Horizontality.” Geology In, 1 Jan. 1970, Available here.
2. “Principle of Original Horizontality.” Wikipedia, Wikimedia Foundation, 5 Feb. 2019, Available here.
3. “Law of Superposition.” Wikipedia, Wikimedia Foundation, 20 Apr. 2020, Available here.

Image Courtesy:

1. “SEUtahStrat” By Matt Affolter (QFL247) (CC BY-SA 3.0) via Commons Wikimedia
2. “IsfjordenSuperposition” By Wilson44691 – Own work (Public Domain) via Commons Wikimedia