Answer:
1. Igneous rocks form when hot, molten rock crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface.
2. Metamorphic series include the Barrovian and Buchan series of metamorphic rocks. George Barrow was a geologist in Scotland who discovered the Barrovian series.[1] These are also called metamorphic facies series. A metamorphic facies series is a sequence of metamorphic facies which plot in a temperature-pressure diagram along a line, and this line represents a certain geothermal gradient. They are not the same as metamorphic zones, as these are defined as a region on a geological map where the pressure-temperature conditions for an index mineral (a mineral that indicates the approximate metamorphic grade of a rock), were appropriate for these minerals to form.
3. Regional metamorphism is metamorphism that occurs over broad areas of the crust. Most regionally metamorphosed rocks occur in areas that have undergone deformation during an orogenic event resulting in mountain belts that have since been eroded to expose the metamorphic rocks.
4. Low-grade metamorphic rocks tend to be fine-grained (the newly formed metamorphic mineral grains that is). High-grade metamorphic rocks tend to be coarse-grained