Cambering is a phenomenon typically seen at a valley crest or plateau margin whereby blocks of competent strata such as sandstone stretch, tilt or rotate with respect to underlying incompetent rock layers such as clay or mudstone.
Gulls are fractures in competent strata that typically form parallel to a valley side in association with cambering.
The gulls may be voids open to the sky or they may be partially or wholly filled with unconsolidated material such as earth or brecciated rock.
Multiple gulls and areas of cambering occur in the Cotswolds where for example the limestones of the Inferior Oolite overlie relatively weak Liassic mudstones.
Recognition of these features is important for engineering geologists advising developers of physical infrastructure such as roads, bridges and dams in such areas.