How Rocks Were Formed: Metamorphic Metamorphic rocks are formed from existing rock by the action of heat, pressure, and chemicals.

Regional Metamorphism Occurs when large areas of rock are under intense heat and pressure, which occurs during mountain-building movements Heat from the friction of moving rock layers is added to the heat already in deeply buried rocks, water and other liquids and gases joins with heat and pressure Regional metamorphism takes place over very large areas Pressure squeezes the grains together Heat and chemicals rearrange the particles, forming or reforming minerals

Metamorphism of Shale The rock becomes more dense and more crystalline The elements recombine to form new minerals like mica and hornblende The pressure squeezes the flakes of mica into parallel layers, along which the rock splits easily: foliation Slate, phyllite, and schist form from regional metamorphism of shale, depending upon the intesity of the metamorphism Phyllite Slate

Schist can form from shales, sandstones, and basalt Gneiss is formed from shale, granite, conglomerate, and many others. It has the coarsest foliation of all the metamorphic rocks. Schist Gneiss

Contact Metamorphism This process occurs when hot magma forces its way into overlying rock The heat of the magma bakes the rock that are in contact with it Hot liquids and gases also enter the intruded rock and react with its minerals Much less rock is affected than in regional metamorphism Changes in the rock are less drastic, with no foliation Hornfels Geology.com Link to Pictures

Rock Cycle

Rock Cycle (with shortcuts)