al-Muzzammil 73:14

Yawma tarjufu'l-arḍu wa'l-jibālu wa kānati'l-jibālu kathīban mahīlā "On the day the earth and the mountains shake; and the mountains become a heap of sand that pours away."

Root: ر-ج-ف. Its concrete sense: to be shaken violently, to tremble, to be moved from its place.

• رَجْفَة (rajfa) — a shaking, an earthquake. In the Qurʾān it is used of the peoples that were destroyed: "So the shaking seized them" (al-Aʿrāf 7/78, 7/91, 7/155; al-ʿAnkabūt 29/37).
• رَاجِفَة (rājifa) — that which shakes; used at al-Nāziʿāt 79/6 of the resurrection.
• إِرْجَاف (irjāf) — unsettling people by spreading baseless news. In the Qurʾān: "…and those who spread baseless news in the city (al-murjifūn)…" (al-Aḥzāb 33/60).

The last derivative is striking: the same root names both the shaking of the earth and the shaking of a society. Rumour and baseless news are what set a community trembling.

The most concrete and most local image in the sūra.

كَثِيب (kathīb) — from the root ك-ث-ب: a sand hill, a dune, a heaped-up mass of sand. The sense of the root is "to gather, to be piled together".

مَّهِيل (mahīl) — from the root ه-ي-ل, a passive participle: that which pours away and scatters when it is trodden on or drawn out from beneath.

Hāla'l-ramla — he poured the sand out, made it run. Ahāla — he made it run, made it slide.

What the word describes is a behaviour everyone who lives in the desert knows: when a handful is taken from the foot of a dune, the sand above runs down to fill the hollow. The heap does not hold; at every intervention it slides.

That is, the verse describes not the disappearance of the mountain but its losing the property of holding together. The mountain is still there — but it is now a heap, and when it is touched it runs.

The Qurʾān describes the state of the mountains at the resurrection with more than one image, and these form a series:

And the series shows an ascent: heap of sand → wool → dust → winnowing → mirage. At each step the matter grows a little lighter, and at the end the appearance remains and the matter does not.

The comparison with manfūsh (carded wool) was treated in al-Qāriʿa; sarāb was taken up in al-Nabaʾ. The link added here is the heaviest end of the series: sand is still matter, still heavy — it simply no longer holds.

And the choice of the comparison is meaningful. In the Arab imagination the mountain is the symbol of fixity and endurance; the Qurʾān qualifies mountains as awtād (pegs, al-Nabaʾ 78/7). Sand, by contrast, is the least stable material of the same country.

That is, the verse turns the most fixed thing of that country into its most unsteady thing. It is not a distant comparison; it is a scene in which the addressee sees both every day.

An observation — as my own reading.

The difference between sand and rock is not a difference of material; it is a difference of grain size. Sand is broken rock.

This is why the verse does not choose a different material. It says the mountain turns into a state that is of the same material but no longer stands together.

And what this describes is this: destruction is not a thing's disappearing; it is the loosening of its bonds. The material stays, what holds it together goes.

I do not present this as a claim in geology and I do not load scientific knowledge onto the verse; that sand is broken rock is something anyone who takes sand in his hand can see. What I record is the aptness in the choice of the comparison.

The two preceding verses had enumerated the recompense of the deniers — and those deniers had been qualified as "the people of ease".

Now what is shaken is the mountains.

The observation recorded in al-Fajr looks here: there the three structures of three peoples (the column, the hewn rock, the peg) were set beside the individual's wealth and it was said that "what is written on stone and what is written on wealth are the same claim to permanence".

The same move is made here: to those who trust in their own firmness, the day is shown on which the firmest-looking thing pours away.

I make this link as my own reading; the verse does not say it openly, but the two verses standing side by side support this reading.