Harivamsha in the mahAbharata - bhaviShyaparva Chapter 34 describes as to how viShNu takes varAha avatAra to lift the Earth from Netherworld
There is a legend of creation in the Taittiriya Brahmana.
In the beginning there was nothing except water and a lotus leaf standing out of it. Prajapati dived in the shape of a boar and brought up some earth and spread it out and fastened it down by pebbles. This was the earth.
Similar story appears in Satapatha brahmana.
He desired, 'May it become more than one, may it reproduce itself!' He toiled and practised austerity; and worn out with toil and austerity, he created foam. He was aware that 'this indeed looks different, it is becoming more (than one): I must toil, indeed!' Worn out with toil and austerity, he created clay, mud, saline soil and sand, gravel (pebble), rock, ore, gold, plants and trees: therewith he clothed this earth.
Peculiarly, a mantra is available in Rig Veda II.20.7
sa vṛtrahendraḥ kṛṣṇayonīḥ purandaro dāsīrairayad vi | ajanayan manave kṣāmapaśca satrā śaṃsaṃ yajamānasya tūtot ||
Smasher of Vr̥tra, splitter of fortresses, Indra razed the Dāsa (fortresses) with their dark wombs. He gave birth to the earth and the waters for Manu. In every way he makes the sacrificer’s laud powerful.
My question is - Was the creation of Earth story has roots in the Rig Veda or somewhere else?