According to wikipedia "The Phalgu or Falgu, a river that flows past Gaya, India in the Indian state of Bihar, is a sacred river for Hindus and Buddhists. Lord Vishnu's Temple Vishnupad Mandir is situated on the bank of Phalgu river."
My question is "Why is this river subterranean?"
I know that according to Hindu mythology it is believed that "During their exile, Rama and Sita decided to rest for a while on the Falgu's sandy banks. When it was time for pind-daan, the offering of food to ancestors to enable them to have peace, Rama went to secure the necessary provisions while Sita waited on the banks. While he was still away, Rama's ancestors appeared in front of her and requested that the ceremony be conducted without delay. Rather than wait for the offerings of food, she performed the ceremony offering sand to the ancestors instead, thereby granting them salvation.
Fearful that her husband would not believe her, she asked the sacrificial fire, a cow, the Falgu, a brahman and a tree to stand witness for her act. Sadly, when Rama arrived on the scene and questioned the witnesses, they all turned false. The hope of a second round of offerings if Rama conducted the ceremony one more time, prompted all the witnesses other than the tree to say that Sita was lying. Enraged, she cursed all the witnesses but the faithful tree. Thus, the Falgu was condemned to run below the ground hiding her head in shame, for all time."
But I want to know what's the scientific geological reason behind it.
Thanks in advance.