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 Word in the desert
Is most attacked by voices of temptation,
The crying shadow in the funeral dance,
The loud lament of the disconsolate chimera.”
—T.S. (Thomas Stearns)
“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)