The way that this form of metamorphism works is that rocks are scraped against each other causing them to be ground into a powder. Then this powder is reformed due to the pressure in the zone and the heat caused by friction of the two rock surfaces.ocks are classified by the processes under which they were formed. The differences in formation account for variations in the appearance of the rocks and, with some practice, you can learn to recognize the different types by sight. Metamorphic Rocks are rocks that have changed form due to heat and pressure.
Growing 4 to 6 feet in height and width, both mophead and lacecap hydrangeas can be used as specimen plants, in mixed borders or in mass plantings. The mountain hydrangea (H. macrophylla subsp. serrata) is a subspecies of bigleaf hydrangea that has slightly smaller leaves and flowers (see image at right).
The upright shrub can grow to 25 feet tall in USDA zones 3 though 8, and blooms on new wood. The showy terminal panicles are up to 8 inches long and blush pink or pale purple as they age. Although panicle is one of the latest hydrangeas to bloom, the flower clusters keep on coming into September.