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:
“Part of every misery is, so to speak, the misery’s shadow or reflection: the fact that you don’t merely suffer but have to keep on thinking about the fact that you suffer. I not only live each endless day in grief, but live each day thinking about living each day in grief.”
—C.S. (Clive Staples)
“I open with a clock striking, to beget an awful attention in the audience—it also marks the time, which is four o’clock in the morning, and saves a description of the rising sun, and a great deal about gilding the eastern hemisphere.”
—Richard Brinsley Sheridan (1751–1816)