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:
“The shadow of the Venetian blind on the painted wall,
Shadows of the snake-plant and cacti, the plaster animals,
Focus the tragic melancholy of the bright stare
Into nowhere, a hole like the black holes in space.”
—John Ashbery (b. 1927)
“Modernity exists in the form of a desire to wipe out whatever came earlier, in the hope of reaching at least a point that could be called a true present, a point of origin that marks a new departure.”
—Paul De Man (1919–1983)