What structures can be found on joints that can reveal their growth history?

What will be an ideal response?


Ans: Joints may show the elliptical arrest lines or hesitation lines that indicate paleo-fracture tip lines and the plumose or feather-like hackles that indicate the propagation direction. Hackles are perpendicular to the arrest lines. Shear fractures are single structures, commonly referred to as surfaces but with a very small thickness (generally <1 mm). A fault is a more composite structure with a thicker zone of strongly deformed rocks (the fault core) in which there may be one or more slip surfaces. A fault also contains a damage zone of deformation bands and/or fractures where strain is much lower than in the fault core.

Environmental & Atmospheric Sciences

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