The Blake concordance shows 324 occurences of the word rock .
The Dome of the Rock is sacred to Judaism, Christianity, and Islam. We can be sure that Blake was fully cognizant of these, and it seems likely in this common awareness he used the terms: Rock of Eternity ( the Rock of eternity), Rock of Ages, Rock of Albion, and many other significant Rocks..
Rock of Eternity:
He [Albion] wept & he divided & he laid his gloomy head
Down on the Rock of Eternity on darkness of the deep
Torn by black storms & ceaseless torrents of consuming fire
Within his breast his fiery sons chaind down & filld with cursings
Rock of Ages:
First Milton saw Albion upon the Rock of Ages,
Deadly pale outstretchd and snowy cold, storm coverd;
A Giant form of perfect beauty outstretchd on the rock
In solemn death: the Sea of Time & Space thunderd aloud
Against the rock, which was inwrapped with the weeds of death
Also FZ1-18.11-15 E310:
Now Man was come to the Palm tree & to the Oak of Weeping
Which stand upon the Edge of Beulah he [Albion] sunk down
From the Supporting arms of the Eternal Saviour; who disposd
The pale limbs of his Eternal Individuality
Upon The Rock of Ages. Watching over him with Love & Care"
Rock of Albion:
Luvah & Vala trembling & shrinking, beheld the great Work master [Urizen]
And heard his Word! Divide ye bands influence by influence
Build we a Bower for heavens darling in the grizly deep
Build we the Mundane Shell around the Rock of Albion
Albion Cold Lays on His Rock
The Rock, above the Sea of Time and Space, lies on the verge of Beulah, where Albion, forgiven and saved, awaits the Resurrection.