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:
“I have often told you that I am that little fish who swims about under a shark and, I believe, lives indelicately on its offal. Anyway, that is the way I am. Life moves over me in a vast black shadow and I swallow whatever it drops with relish, having learned in a very hard school that one cannot be both a parasite and enjoy self-nourishment without moving in worlds too fantastic for even my disordered imagination to people with meaning.”
—Zelda Fitzgerald (1900–1948)
“The unread story is not a story; it is little black marks on wood pulp. The reader, reading it, makes it live: a live thing, a story.”
—Ursula K. Le Guin (b. 1929)