What are two sources of the heat and pressure that cause metamorphism?

There are two sources of heat, one comes from the geothermal gradient - the increase in temperature that occurs with increase in depth in the earth. The average Geothermal Gradient is approximately 1 degree C for every 30 meters (~100 feet) of depth, although under local conditions it may vary from this ideal.

    The second source of heat is from intrusive bodies of magma, such as Batholiths. As these bodies cool they release heat to the surrounding country rock, leading to metamorphism.

Explanation:

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.