Many other instances mentioned in the scriptures can actually refer to geological events. First is the incident of Indra killing the dragon Vritra and releasing the life-giving waters which could actually be a poetic description of Indra's lightening splitting open a mountain to make way for water that had been till then perhaps dammed in the form of a lake. Check the Rig Veda Verse 1.32.10-12:
10 Rolled in the midst of never-ceasing currents flowing without a rest for ever onward.
The waters bear off Vṛtra's nameless body: the foe of Indra sank to during darkness.
11 Guarded by Ahi stood the thralls of Dāsas, the waters stayed like kine held by the robber.
But he, when he had smitten Vṛtra, opened the cave wherein the floods had been imprisoned.
12 A horse's tail wast thou when he, O Indra, smote on thy bolt; thou, God without a second,
Thou hast won back the kine, hast won the Soma; thou hast let loose to flow the Seven Rivers.
Again Verse 1.51.4, 1.52 and Verses 1.54.1 & 10 also seem to point to a major geological change resulting from this feat of Indra:
1.51.4 Thou hast unclosed the prisons of the waters; thou hast in the mountain seized the treasure rich in gifts.
When thou hadst slain with might the dragon Vṛtra, thou, Indra, didst raise the Sun in heaven for all to see.
1.52.14 Whose amplitude the heaven and earth have not attained, whose bounds the waters of mid-air have never reached,—
Not, when in joy he fights the stayer of the rain: thou, and none else, hast made all things in order due.
1.52.15 The Maruts sang thy praise in this encounter, and in thee all the Deities delighted,
What time thou, Indra, with thy spiky weapon, thy deadly bolt, smotest the face of Vṛtra.
1.54.1 URGE us not, Maghavan, to this distressful fight, for none may comprehend the limit of thy strength.
Thou with fierce shout hast made the woods and rivers roar: did not men run in crowds together in their fear?
1.54.10 There darkness stood, the vault that stayed the waters’ flow: in Vṛtra's hollow side the rain-cloud lay concealed.
But Indra smote the rivers which the obstructer stayed, flood following after flood, down steep declivities.
There are many more verses that wax eloquent on this particular feat of Indra and it could certainly be a big geological event:
R.V. 1.62.6 This is the deed most worthy of all honour, the fairest marvel of the Wonder-Worker,
That, nigh where heaven bends down, he made four rivers flow full with waves that carry down sweet water.
R.V. 2.15.88 Praised by the Aṅgirases he slaughtered Vala, and burst apart the bulwarks of the mountain.
He tore away their deftly-built defences. These things did Indra in the Soma's rapture.
Even the Puranas have plenty of references some of whom have been covered in the other answers. I'll share one of the biggest geological events in our history - Saraswati's arrival on earth. The Skanda Purana Section VII.1. 33. 11-100 & Chapter 34 detail the story of how Saraswati was forced to arrive on earth in order to take a terrible devastating fire to the ocean so that it would not destroy the whole world. This fire known as the Vadavagni was generated by Rishi Aurva and the verse also give an idea of the various locations associated with the river:
11-12. Ganga said: O Lord, O master of the worlds, I do not have the strength to carry Aurva. He is huge and terrific in form. This Anala (Fire) burns excessively. Thereupon the liberal-minded Lord spoke to Yamuna first, to Sindhu thereafter, and to various rivers severally.
13-15. They were asked by the excellent one among Suras and they proved unable to take (Aurva). Then Janardana, the Lord of Devas, spoke to Sarasvati: “O auspicious one, you yourself go over to the west of the briny sea. If this is carried out, all the Suras will be rid of their fear. Otherwise they will be burned by the Vadava through its refulgence. So, save Vibudhas (Suras)
from this terrible fear.
21-23. On hearing the words uttered by Visnu, the Great-
grandfather sniffed the head of his virgin daughter and said
lovingly: “O fair lady, do go. Save all the Devas caught in the
midst of fearful danger. Take this Vadava with you and cast it
into the salt sea.” On hearing her father’s words she said:
Sarasvati said: At your instance, O dear father, I am now setting out
undoubtedly. This Vadava fire is very horrendous. He will consume
my body.
24-30. It is the advent of the terrible Kali Age now on the
earth. O Lord, folks of evil conduct will be coming into contact
with me. What can be more painful than contact with sinners!
The next verses actually give the reason why the river disappears at certain places and resurfaces at others:
Brahma said: If you do not like the earth’s surface fully infested with
sinful folks, do take the Vahni (Fire) to the great ocean con-
fining yourself to the Patalatala (nether worlds).
44-48 With the rapidity of her current, she pierced the ground
and came to the surface of the Earth. Whenever she (the river)
became weary and got scorched by the Vadava fire, the river
became visible in the mortal world. Thereupon, Praci (Eastern quarter) became scorched by the Vadava. Thereat all the Tirthas glorified by the ancient
seers, O beautiful woman, the Tirthas of heaven, intermediate
space and the earth asserted their presence there. On being
consoled by them, the river Sarasvati went over to the nether
worlds to the ocean, the abode of sharks and
crocodiles. O beautiful woman among the Suras, she (river) reached
Khadiramoda and there saw the ocean. Afterwards she took up
the Vahni and began to proceed onwards. She thought of the fact that it was at the behest of the Lord that she had herself taken up the burden and was there-
fore delighted. With a clear conscience, she went ahead facing
the South.
The next verses mention how she splits into five channels just before entering the ocean. This is clearly the description of a delta formed by the river before she joins the sea:
52-56. Thereupon, she began to reflect, ‘How can I attain
some merit!’ Further the chaste lady (river) was afraid of the
curse (of the sages). She then turned herself into one of five
channels. O lady of excellent complexion (Gauri), she propiti-
ated each of the sages. Then, she had five different names on
the earth. They are: HarinI, VajrinI, Nyariku, Kapila, and Sarasvati.
The river Sarasvati flowing in five channels shall dispel all the
five sins of men if they plunge into it or drink the waters.
The next verses even mention the destruction of a mountain standing in its path probably referring to an actual geographical event:
88-89. “I am alone and isolated. I lament. Still if you are
inclined to marry me, hold this Vadava in your hands while I
take my holy bath.” 89. When this was said, Krtasmara, the excellent Moun-
tain, seized the Vadava handed over by Sarasvatl. Due to its
contact, Krtasmara was reduced to (a heap of) ash insta-
ntly.
- After burning Krtasmara and holding the Vadava once
again, the divine lady (river) came near the sea and stood
there with hairs standing on end due to delight.
I hope these references help you understand some of the geological events from ancient scriptures.
