|
|
|
|
|
|
|
|
|
|
|
|
| The
Earth´s crust as well as being intruded by magma, is from time to time subjected
to stresses generated within the crust and mantle which are sufficiently
great to cause it to break to form faults, and also to bend forming folds.
These forces are often concentrated along relatively narrow, sinuous belts when the folding, usually combined with intrusion and extrusion of magma, gives rise to mountain chains. The rocks within a mountain chain not only sustain considerable pressures but are also heated both generally and by the large scale of intrusion of magma, with the effect that rocks are deformed and recrystallized to varying degrees. Such rocks are called metamorphic rocks. (Hamilton et al 1976, 148) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|