Exfoliation Joint - General Characteristics of Exfoliation Joints

General Characteristics of Exfoliation Joints

• Commonly follow topography (Gilbert, 1904; Matthes, 1930; Goodman, 1993).
• Divide the rock into sub-planar slabs (Goodman, 1993).
• Joint spacing increases with depth from a few centimeters near the surface to a few meters (Dale, 1923; Jahns, 1943; Goodman, 1993).
• Maximum depth of observed occurrence is around 100 meters (Dale, 1923; Jahns, 1943; Holzhausen, 1989; Goodman, 1993).
• Deeper joints have a larger radius of curvature, which tends to round the corners of the landscape as material is eroded (Gilbert, 1904; Dale, 1923; Matthes, 1930; Jahns, 1943; Goodman, 1993).
• Fracture mode is tensile (Bahat et al., 1999; Mandl, 2005).
• Occur in many different lithologies and climate zones, not unique to glaciated landscapes (Bradley 1963; Twidale, 1973; Goodman, 1993).
• Host rock is generally sparsely jointed, fairly isotropic, and has high compressive strength (Gilbert, 1904; Jahns, 1943; Twidale, 1973).
• Can have concave and convex upwards curvatures (Gilbert, 1904; Matthes, 1930; Romani and Twidale, 1999).
• Often associated with secondary compressive forms such as arching, buckling, and A-tents (buckled slabs) (Romani and Twidale, 1999).