"Geologists have found that streams in the Karoo basin of South Africa changed suddenly at the end of the Permian period 250 million years ago"

The part of the sentence mentioned above is an independent clause. The From... To.... Structure modifies not just the part right before the comma. It is modifying the "streams...changed suddenly" and hence informing us that the streams changed suddenly from x shape to y pattern. We can look at the proximity of the phrase and determine that this is a case of the absolute phrase.

For more, check out, https://grockit.com/blog/gmat/2011/09/06 ... te-phrase/

Interesting. So is the absolute phrase allowed to start with prepositions? The typical pattern that I've seen so far was "Main clause, noun + modifier".

Yes. That is mostly the pattern, "Main clause, noun + modifier". But, mostly not always. As in the case above, the IC before the comma has been modified by the phrase after the comma.

PFB a link which may be of help :
https://www.testmagic.com/grammar/explan ... uction.asp

I couldn't find a better source At this point if you have any more doubts, call in the experts Coz m learning just like you.

Thanks a lot, digvijayk. Those links were very useful.

This is not an absolute modifier here. This is simply a prepositional modifier - and since all prepositional modifier with comma act as an adverb, this too does.

Absolute phrase is composed of a noun and a noun modifier.

Researchers have found alarming levels of radioactivity in certain species of ferns, findings(noun) that suggest the detrimental effects of nuclear power plants in nearby areas ( noun modifier - a relative clause).

The coach tried to put 5 receivers on the line, a strategy(noun) that failed (relative clause). - from Ron's Thursday session.

His head (noun) held high(adjective), John went out of the room. - MGMAT SC example

Here, "from the meandering shape typically found in well-vegetated zones to the braided patters found in areas without deep-rooted vegetation to hold the soil together" is just a prepositional phrase acting as an adverb of manner.

yes, both are adverbs, but not an absolute phrase.


Hope this helps !!