Metamorphic rocks


Some rocks, originally deposited as sediments, may be severely changed by the effects of heat and pressure; these are called metamorphic rocks. Intense heat may alter the minerals of which the original sedimentary rock was composed, while immense pressures associated with major earth movements may buckle and deform the original bedding, as in this example of an intensely deformed marble from Co. Donegal.

Fossils can still be found in metamorphic rocks if they have not been too severely altered, but very often all trace is obliterated of any fossils that the rock might once have contained.

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