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HomeNews ReportsAs ASI begins scientific survey of Gyanvapi structure, read how archaeologists determine age and...

As ASI begins scientific survey of Gyanvapi structure, read how archaeologists determine age and other aspects of ancient buildings and sculptures

ASI has assured the court it will be a non-invasive survey, and there will be no digging at the site and no damage would be caused to the structure by the methods used.

The Archaeological Survey of India (ASI) team arrived at the Gyanvapi mosque premises adjacent to the Kashi Vishwanath Temple in Uttar Pradesh’s Varanasi on Friday morning and began a scientific assessment of the complex amid tight security after Allahabad High Court gave the go-ahead for the survey. While the nation has its eyes set on what the findings of the ASI will reveal, let’s understand how the archaeologists determine the age, time and style of sculptures as well as what methods ASI will be using at the Gyanvapi survey site in Varanasi. 

It is notable that ASI has assured the court it will be a non-invasive survey, and there will be no digging at the site and no damage would be caused to the structure by the methods used.

Stone sculptures can be dated by style, strata and other traits. Several methods such as relative dating are employed by archaeologists for the same. 

Relative Dating 

The relative dating method is a technique for determining the chronological sequence of artefacts without knowing their actual age. It refers to the stratigraphic or archaeological age of a specimen or formation. These archaeology dating techniques can be used to assess the relative ages of fossils or artefacts in a collection without knowing their exact absolute ages. 

A pillar at Gyanvapi disputed site (Image via IndiaToday)

Seriation

Seriation is another method that examines variations for certain forms of objects found at a site. A chronology is established on the concept that one ethnic design would gradually replace an old style over the period. It is used in situations where absolute dating methods like radiocarbon cannot be applied. Seriation can be used to date stone tools, pottery fragments etc.

The method basically arranges various objects found at a site in chronological order. While this method does tell the exact age of an object, it can identify the older and newer objects at a site.

Carbon 14 dating 

It is notable that the Hindu plaintiffs in the Gyanvapi case in their plea had sought permission for carbon dating of the Shivling found on the disputed Gyanvapi compound, walls and other structures on the premises. In this context, it is important to understand, what carbon dating is and how it works.

Radiocarbon dating, often known as carbon-14 dating, is a scientific process that can establish the age of organic materials as old as 60,000 years. Willard Libby invented the approach in the late 1940s at the University of Chicago. The carbon-14 dating method is based on the idea of radiative decay of Carbon-14 isotopes over thousands of years. 

Graphics representing how carbon-14 dating works (Image via Byjus)

Carbon dating cannot be used in all situations. It cannot be used to establish the age of non-living things such as rocks.

Carbon-14 dating is one of the many techniques under a broader term Radiometric dating. 

Radiometric dating is a method of determining the age of anything based on the presence of a radioactive isotope within it, such as a wooden object, a rock, or a fossil. Radiometric dating uses a short-lived radioactive element to establish the age of geologic materials. Carbon-14 and potassium-14/argon-40 dating procedures are the most advanced.

The basic premise of radiometric dating is that by comparing the presence of a radioactive isotope in a sample to its known abundance on Earth and its known half-life (rate of decay), one can compute the age of the sample.

One of the method’s shortcomings is that it cannot date a sculpture. That is why, geologists employ materials with longer half-lives. For example, the half-life of potassium-40 decaying to argon is 1.26 billion years, and the half-life of beryllium-10 decaying to boron is 1.52 million years. Geologists use the abundance of these radioisotopes to date rocks.

Ground Penetrating Radar 

A GPR survey, or ground penetrating radar survey, is a geophysical imaging radar technique that uses radio waves to obtain photographs of entities below ground level without digging up the soil. The things that need to be photographed should not be too deep in the ground (no more than tens of metres below ground level). The ASI team will be conducting a GPR survey at the area below the three domes at Gyanvapi disputed site to determine if the Gyanvapi ‘mosque’ is constructed over a pre-existing structure of a Hindu temple.

GPR Surveys are used to determine the exact location of natural or man-made objects underneath, natural elements, or to identify changes in their position. It takes pictures by sending high-frequency (50 – 1,500MHz) electromagnetic pulses into the ground. The transmitter and the antenna are the two most important pieces of equipment in GPR systems. The transmitter, which would be near the ground, would deliver radar signals to the earth, and the antenna would detect the reflected signals. The received signals would be analysed and shown on a graphic recorder. 

Effect of a buried object on the radar signal reflection (Image via ScienceDirect)

A good GPR survey yields data lines that reflect a segment image of the earth’s subsurface. All of the lines collected in a given area would be combined and utilised to create a 3D depiction of the surveyed area. Ground Penetrating Radar signals may identify and capture images of concrete, plastic, natural materials, metal, and other materials.

While the Archaeological Survey of India (ASI) surveys the Gyanvapi complex in Varanasi, the Anjuman Intezamia Masjid Committee has appealed the Allahabad High Court ruling to the Supreme Court. The Masjid Committee’s counsel sought that the Supreme Court rule against a high court order allowing ASI to conduct the survey. However, Supreme Court says it will look into the issue.

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