Shadow marks are a form of archaeological feature visible from the air. Unlike cropmarks, frost marks and soil marks they require upstanding features to work and are therefore more commonly seen in the context of extant sites rather than previously undiscovered buried ones.
They are caused by the differences in height on the ground produced by archaeological remains. In the case of ancient, eroded earthworks these differences are often small and they are most apparent when viewed from the air, when the sun is low in the sky. This causes long shadows to be cast by the higher features, which are illuminated from one side by the sun, with dark shadows marking hollows and depressions.
Shadow marks are best viewed obliquely rather than from directly above in order to emphasise the effect of the shadows.
Famous quotes containing the words shadow and/or marks:
“Beneath the sun’s rays our shadow is our comrade;
When clouds obscure the sun our shadow flees.
So Fortune’s smiles the fickle crowd pursues,
But swift is gone whenever she veils her face.”
—Ovid (Publius Ovidius Naso)
“I regard almost all quarrels of princes on the same footing, and I see nothing that marks man’s unreason so positively as war. Indeed, what folly to kill one another for interests often imaginary, and always for the pleasure of persons who do not think themselves even obliged to those who sacrifice themselves for them!”
—Mary Wortley, Lady Montagu (1689–1762)