From sea +stack(“a heap, pile; large vertical column of rock in the sea”); stack is derived from Middle Englishstak(“a heap, pile, stack; large vertical column of rock in the sea”)[and other forms],[1] from Old Norsestakkr(“a heap, pile; haystack; barn”) (compare Faroesestakkur(“sea stack”)),[2] from Proto-Germanic*stakkaz(“pile of hay, haystack”), ultimately from Proto-Indo-European*(s)teg-(“beam, pole, stick”).
1854 May 15, “Notes on Books”, in Norton’s Literary Gazette and Publishers’ Circular, volume I (New Series), number X, New York, N.Y.: Baker, Godwin & Co.,[…] [for Charles Benjamin Norton], →OCLC, page 248, column 3:
The sea-gull sprang upwards from where he had floated on the ripple, and hied him slowly away to his lodge in his deep sea-stack; the dusky cormorant flitted past, with heavier and more frequent stroke, to his whitened shelf high on the precipice;[...]
That this defile may have been partly eroded by the action of the sea is also very probable; and there are certain isolated pinnacles and irregular columns of agglomerate in its immediate neighbourhood which have all the appearance of being old sea-stacks.
1895, Grenville A[rthur] J[ames] Cole, “Along the Shore”, in Open-air Studies: An Introduction to Geology Out-of-doors (Griffin’s Scientific Text Books), London: Charles Griffin and Company, […], →OCLC, page 94:
The sea, with its tremendous battering-power, is excavating caves, just as the streams make pot-holes; only the action is horizontal, rather than vertical, the water lashing like a whip around the flanks of the sea-stacks and islets.
Off the shore of still another island they found a stand of sea stacks, weird towers of rock sculpted by sand and wind and engulfed in flocks of gulls and cormorants, and as they banked for another look, Kate saw three bald eagles take wing.
2004, J. Murray Neil, “Hills of Hoy”, in The Scots Fiddle: Tunes, Tales & Traditions of the Western Highlands, Hebrides, Orkney & Shetland, Glasgow: Neil Wilson Publishing, published 2012, →ISBN, page 157:
Lying off the north-west coast of the island is the Old Man of Hoy, the most famous sea stack in the world. At a height of 450ft it dominates the neighbouring cliffs of which it was once part.
A tall island in the sea, a geologic bone, the sea stack represents rock harder than what once surrounded it and has been eroded away. [...] The sea stack—which in desert country might be called a chimney, pinnacle, needle, knob, horn, or pillar—rises in the ocean, and is often favored by cormorants, puffins, and gulls for nesting and whitewashing with clamorous possession.
2009, Claudia Nice, Down by the Sea with Brush & Pen: Draw and Paint Beautiful Coastal Scenes, Cincinnati, Oh.:North Light Books, →ISBN:
Some sea stacks are far off shore, while others like the one on the facing page, are in the tidal zone. Consider for a moment the contrasts the sea stack brings to the painting.