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FOLDS AND STRUCTURES DUE TO FOLDING.
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Folding generally takes place in areas of sedimentary rocks that have been laid down in horizontal layers called strata. When compression produces thrust [convergence], the earth folds along lines of strength and weakness. This creates long ranges of FOLD MOUNTAINS – Alps, Himalayas, Rockies…
Faulting –adjacent surfaces are displaced relative to one another
Normal Fault • In normal faulting, the hanging wall block moves down relative to the footwall block. • Normal faults are associated with crustal TENSION.
Reverse Fault • In reverse faulting, the hanging wall block moves up relative to the footwall block. • Reverse faults are associated with crustal COMPRESSION and are also known as thrust faults.
A horst occurs when a mass of the earth's crust that lies between two faults and is higher than the surrounding land.
A graben is an elongated depression between geologic faults.
Strike-slip Fault • In strike-slip faulting, the two blocks move either to the left or to the right relative to one another.