Joints

Joints

• Joints are produced by tensional forces. These forces may be a result of folding, cooling or unloading rocks.
• They give rocks a blocky appreance when they outcrop at the earths surface.
• Joints will only form in competent rocks, these are brittle and break when put under tension.
• Include: sandstone, limestone and grantie.
• Joints in sedimentary rocks are usually found perpendicular to the beds.

Joints formed by folding (Tectonic Joints)

• Produced by tension created in rocks when they are folded by earths movements.
• Compressive forces fold the rocks but cause some of the surrounding rocks to be put under tensional pressure.
• The rocks fracture because the outer surface of the bed is stretched more than the inner surface.
• The rock is conpetent so does not change thickness…