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:
“Erasmus was the light of his century; others were its strength: he lighted the way; others knew how to walk on it while he himself remained in the shadow as the source of light always does. But he who points the way into a new era is no less worthy of veneration than he who is the first to enter it; those who work invisibly have also accomplished a feat.”
—Stefan Zweig (18811942)
“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)