silathoranam

 

This notified National Geo-heritage Monument is a distinctive geological feature. The arch is also called Silathoranam in the local language (Telugu language: sila means ‘rock’ and thoranam means a garland strung over a threshold, connecting two vertical columns or an ‘arch’ as in this case). The arch is naturally formed in the quartzites of Cuddapah Supergroup of Middle to Upper Proterozoic (1600 to 570 Ma) due to natural erosive forces. In the 1980s, during excavations for a geological fault in the Tirumala hills, geologists found this rare geological formation of the rock arch which has two dissimilar sets of rocks with a connecting thin link. The assessed geological age of the rock arch is 2.5 million years. Formation of the arch is attributed to intensified weathering and erosion of stream action that has withstood the torque of nature. This is a rare geological fault which is technically called in the geological idiom as ‘Eparchaean Unconformity.