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.Continue Reading
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
Chemical weathering is the decomposition and disintegration of rock due to chemical reactions. According to Eastern Illinois University, chemical agents break down the bonds holding rocks together, causing the rocks to fall apart, forming smaller and smaller pieces over time. Chemical weathering includes dissolution, oxidation and hydrolysis.Full Answer >
A laccolith is a geological structure that forms when magma pushes through layers of rock above it and pools in a dome shape. Laccoliths are characterized by their shape, as they are typically flat on the bottom and rounded or dome shaped on top. These structures are also called plutonic formations or igneous intrusions, which are related to sills.Full Answer >
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 >