Difference Between Absolute and Relative Dating

The main difference between absolute and relative dating is that the absolute dating is a technique to determine the numerical age of a rock or a fossil whereas the relative dating is a technique that determines the relative age. Furthermore, absolute dating can be done with the use of radiometric dating while relative age is determined with respect to other layers.

Absolute dating and relative dating are two techniques used in geology to evaluate the age and the period of a fossil or rock.

Key Areas Covered

1. What is Absolute Dating
     – Definition, Facts, Methods
2. What is Relative Dating
     – Definition, Facts, Methods
3. What are the Similarities Between Absolute and Relative Dating
     – Outline of Common Features
4. What is the Difference Between Absolute and Relative Dating
     – Comparison of Key Differences

Key Terms

Absolute Dating, Amino Acid Dating, Dendrochronology, Methods of Dating, Numerical Dating, Radiometric Dating, Relative Dating, Thermoluminescence

What is Absolute Dating

In geology, absolute dating is a technique that determines the exact numerical age of a historical remaining. Since it evaluates the exact age of the sample, absolute ageing is also called numerical dating. The four techniques used in absolute dating are radiometric dating, amino acid dating, dendrochronology, and thermoluminescence.

1. Radiometric dating: It determines the age of the sample by measuring the amount of a particular radioactive isotope present in the sample. The age can be determined by the rate of decay of that particular isotope. The type of radioactive isotope used depends on the type of sample. One of the most popular and widely used types of radioactive isotope in this type of techniques is the carbon-14.
   

   Figure 1: Radiocarbon Date Calibration Curve

2. Amino acid dating: The change in the protein content of a biological sample can be used to determine the age. A particular form of a living being may have a defined protein content in their bodies that deteriorates with the time.
3. Dendrochronology: The number of annual growth rings of a dicot is used in this technique to determine the age of the tree.
4. Thermoluminescence: This technique determines the final period during which the object absorbs light, emitting electrons. The age is determined with respect to the emissions.

What is Relative Dating

Relative dating is the technique used to determine the age by comparing the historical remaining to the nearby layers. It is a less advanced technique when compared to absolute dating. Some methods used in relative dating are stratigraphy, biostratigraphy, and cross dating.

1. Stratigraphy: This technique assumes that the lowest layer is the oldest while the topmost layer is the youngest layer. It is one of the oldest methods of relative dating.
   

   Figure 2: Igneous Rock Layers

2. Biostratigraphy: In this technique, the faunal deposits such as fossils of dead animals are used to establish a strategy for dating. It is an extended version of the stratigraphy.
3. Cross dating: In this method, the fossils of one layer are compared with another layer with known dating.

Similarities Between Absolute and Relative Dating

• Absolute and relative dating are the two types of techniques used to determine the age of a historical remaining.
• Both techniques help to understand the order of formation of the historical remaining.

Difference Between Absolute and Relative Dating

Definition

The absolute dating refers to a technique used to determine the exact age of the artefact or a site using methods such as carbon dating while relative dating refers to a technique used to determine which object or item is older in comparison to the other one.

Significance

Absolute dating determines the numerical age while relative dating arranges the fossils in an order.

Methods

The four methods involved in absolute dating are radiometric dating, amino acid dating, dendrochronology, and thermoluminescence while biostratigraphy, stratigraphy, and cross dating are involved in the relative dating.

Precision

The precision in absolute ageing is high while the precision of the relative ageing is low.

Quantitative/Qualitative

Absolute age is a quantitative measurement while relative age is a qualitative measurement.

Work Better for

Absolute dating works better for igneous and metamorphic rocks while relative dating works better for sedimentary rocks having layered arrangement of sediments.

Cost and Time

Absolute dating is expensive and takes time while relative dating is less-expensive and efficient.

Conclusion

Absolute dating is the technique that determines the exact age of a historical remaining while relative dating gives the order of age of several samples. Therefore, absolute dating is a quantitative measurement while relative dating is a qualitative measurement. The main difference between absolute and relative dating is the precision of the measurement.

Reference:

1. “Absolute Dating.” Science Learning Hub, Available Here
2. “Relative Dating.” Science Learning Hub, Available Here

Image Courtesy:

1. “Radiocarbon Date Calibration Curve” By HowardMorland – Own work based on information from: Reimer, P.J., et al. C.E. (2004). “IntCal04 Terrestrial radiocarbon age calibration”. Radiocarbon 46: 1029-58. (CC BY-SA 3.0) via Commons Wikimedia     
2. “Relative dating of fossils” By Jillcurie – Own work (CC BY-SA 3.0) via Commons Wikimedia