What are PTT paths discuss different types of PTT paths?
The P-T-t paths are generally classified into two types: clockwise P-T-t paths, which are related to collision origin, and involve high pressures followed by high temperatures; and anticlockwise P-T-t paths, which are usually of intrusion origin, and involve high temperatures before high pressures.
How do you identify metamorphism retrograde?
In general, the changes in mineral assemblage and mineral composition that occur during burial and heating are referred to as prograde metamorphism, whereas those that occur during uplift and cooling of a rock represent retrograde metamorphism.
What is prograde metamorphism?
Prograde metamorphism refers to the changes in a rock that accompany such increasing metamorphic grade. Retrograde refers to decreasing grade as a body of rock cools and recovers from a metamorphic or igneous event, and retrograde metamorphism describes any accompanying changes.
What are some ways in which geologists can determine the temperatures and pressures of metamorphism?
Therefore, by studying the mineral composition of a metamorphic rock, geologists can determine the temperature at which the rock has formed. Metamorphic mineral assemblages are natural geothermometers. The depth at which metamorphism occurs depends on the geothermal gradient.
What metamorphic rocks are formed at high pressures and temperatures?
Foliated metamorphic rocks are formed within the Earth’s interior under extremely high pressures that are unequal, occurring when the pressure is greater in one direction than in the others (directed pressure).
How do temperature and pressure affect metamorphism?
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.
What is Mercury retrograde?
Mercury normally moves faster than Earth around the sun. But when Mercury is retrograde, it is moving slower than Earth around the sun. (Mercury usually moves 88 days around the sun versus the 365 days that Earth does.) This creates an optical illusion in which we think that Mercury is moving backward.
What is the difference between retrograde and prograde?
Prograde refers to an object that spins in the same direction as its orbit. Retrograde refers to an object that spins in the opposite direction of its orbit.
What is the difference between prograde and retrograde metamorphism?
How do temperature and pressure affect the metamorphism?
What happens to the rock temperature?
Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand (with heat) and contract (with cold). As this happens over and over again, the structure of the rock weakens. Over time, it crumbles.