That would be if the action that stopped it would depend on Vivec's power, but as it depends on love of the people for Vivec, Vivec's power is not required to hold it up.
"I would have done so myself if I wanted, silly Hortator. I shall keep it there with its last intention intact, so that if the love of the people of this city for me ever disappear, so shall the power that holds back their destruction."
http://www.gamesas.com/bgsforums/index.php?showtopic=821219#
Also, the story of Lie Rock, and vivec's halting it has many (poorly) veiled sixual themes.
Lie Rock is "born from Vivec's second aperture.", and his act of suspending it's decent makes the act of "piercing the second aperature forbidden"-- If we suppose that Lie Rock is a "Turd", and that Vivec's "Second Aperature" is his butt, (which is where turds come from) it stands to reason that homosixual male six is now forbidden after vivec jabbed his muatra into the lie rock. (Apparently Vivec didnt like it.
)
Spear Biting is also "Forbidden" now, because of the Pomegranate Banquet. So, I guess feilatio is out too.
I suppose one could use these mythic precepts against these sixual practices, and use them to concoct some rather sanguine rituals of immense power, but I wont go there.
The whole sermons thing seems preoccupied with various sixual acts.
Still-- What is "Land Fall"?
People stop loving vivec -> Vivec's Giant Turd lands on Vvardenfell -> Nearly everyone dies.