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:
“Whether changes in the sibling relationship during adolescence create long-term rifts that spill over into adulthood depends upon the ability of brothers and sisters to constantly redefine their connection. Siblings either learn to accept one another as independent individuals with their own sets of values and behaviors or cling to the shadow of the brother and sister they once knew.”
—Jane Mersky Leder (20th century)
“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)