The responsibility of sustaining the earth well has been given by MahaVishnu to the men of Dharma in the beginning of creation. The story is told in the 𝗩𝗶𝘀𝗵𝗻𝘂 𝗦𝗮𝗺𝗵𝗶𝘁𝗮, chapter 1, which is an Agama text.

In the beginning of creation, Vishnu took his Varaha form, and lifted the earth from the depths of the primordial ocean. Once lifted, He left the earth and retired to a place out of normal visibility.

Earth was worried. Now that Janardana has left, who will sustain her? Bhudevi took form of a mesmerizing woman, and walked to Kashyapa to ask this very question. Her brilliance of her beauty was such the heavens and the world around were alight.

Kashyapa knew the question in her mind, and told her to go to Vishnu Himself, who is now retired to His abode in the Ksheer Sagara, on the bed sustained by Aadi-Shesha. Vishnu was lying resplendent there, bright like a thousand suns.

On receiving that very vision, she felt as if all the bad karma from eons past just evaporated from her being.

Finally, she asked, "You have to put me to my proper place by lifting me. But who will now sustain me, now that you have retired to your abode?"

"Persons proficient in the shashtras, conversant with the rules of varnashramas, will sustain you. Your charge has been given to them now."

She then sang praises to Vishnu, and requested Him to elaborate to her what are the rules of the varnashramas. What would be their duties, right conducts, and the esoteric interpretations of the same.

Shree Vishnu obliged, and described it to her. For the details, read Vishnu Samhita!

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