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:
“Yet there is a mystery here and it is not one that I understand: without the sting of otherness, of—even—the vicious, without the terrible energies of the underside of health, sanity, sense, then nothing works or can work. I tell you that goodness-what we in our ordinary daylight selves call goodness: the ordinary, the decent—these are nothing without the hidden powers that pour forth continually from their shadow sides. Their hidden aspects contained and tempered.”
—Doris Lessing (b. 1919)
“If any personal description of me is thought desirable, it may be said, I am, in height, six feet, four inches, nearly; lean in flesh, weighing, on an average, one hundred and eighty pounds; dark complexion, with course black hair, and grey eyes—no other marks or brands recollected.”
—Abraham Lincoln (1809–1865)