This is an irregular verb and the conjugations need to be memorized. A short lesson explains how. Mentir - French Verb Conjugations Learn how to conjugate mentir, an irregular -ir French verb. This is not an easy verb to conjugate, so you will need a good lesson to show you how.
Metamorphism occurs because some minerals are stable only under certain conditions of pressure and temperature. When pressure and temperature change, chemical reactions occur to cause the minerals in the rock to change to an assemblage that is stable at the new pressure and temperature conditions.
As the temperature and/or pressure increases on a body of rock we say the rock undergoes prograde metamorphism or that the grade of metamorphism increases. Metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form.rade of Metamorphism. 1  Note that Diagenesis is also a change in form that occurs in sedimentary rocks. 2  Metamorphism, therefore occurs at temperatures and pressures higher than 200 o C and 300 MPa. 3  The upper limit of metamorphism occurs at the pressure and temperature where melting of the rock in question begins.