Metamorphic rock is formed underground through a process that changes a rock's molecular structure due to pressure, heat and chemical reactions. A metamorphic rock forms from a parent rock called a protolith. Depending on conditions, a protolith can transform into any metamorphic rock. Because protoliths are capable of undergoing vast changes, identifying them is sometimes difficult for geologists.Know More
Under extreme pressures, such as between two colliding tectonic plates, the minerals of a metamorphic rock group together and align to form foliation, which appears as stripes in the rock. One example of a heavily foliated rock is gneiss.
Alternatively, highly heated areas, such as near magma chambers, produce vastly different metamorphic rocks. One example is hornfels.
Another area for metamorphism is at a subduction zone where oceanic plates collide with and bend under continental plates. Because these high-pressure areas are near the ocean, they are cooler and produce different metamorphic results. One example of this is the creation of a blue mineral called glaucophane. This mineral in the rock foliates from high pressure and creates blueschist, a blue-tinted version of schist.
A protolith may change a number of times before reaching its final metamorphic stage. For example, gneiss may begin as shale that turns into slate, phyllite, schist and finally gneiss.Learn more about Geology
The rock cycle is the transformation of one type of rock to another through heat, pressure, weathering and erosion. First proposed by James Hutton in the late 18th century, the cycle is an ongoing process that affects the rock that composes mountains as well as rock deep below the Earth’s surface. However, it is important to realize that not all rocks go through every stage of the cycle.Full Answer >
Talc is a metamorphic rock, which means it was originally a different kind of rock that changed under heat and pressure. Talc is composed of hydrated magnesium silicate, and its chemical formula is Mg3Si4O10(OH)2.Full Answer >
"Seafloor spreading" is a process that produces basalt, a rock that makes up the ocean's crust. Seafloor spreading takes place at mid-ocean ridges. Two examples of such ridges are the Mid-Atlantic Rise and the East Pacific Rise.Full Answer >
Marble is formed from limestone when the limestone is affected by heat and high pressure during a process known as metamorphism. During metamorphism the calcite limestone recrystallizes, forming the interlocking calcite crystals that make up the marble.Full Answer >