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Flow banding is the result of a process of fractional crystallization which occurs by convection, if the crystals which are caught in the flow-banded margins are removed from the melt. The friction and viscosity of the magma causes phenocrysts and xenoliths within the magma or lava to slow down near the interface and become trapped in a viscous ...
These rocks are fine-grained and sometimes cool so rapidly that no crystals can form and result in a natural glass, such as obsidian, however the most common fine-grained rock would be known as basalt. Any of the three main types of rocks (igneous, sedimentary, and metamorphic rocks) can melt into magma and cool into igneous rocks. [2]
Grain size in igneous rocks results from cooling time so porphyritic rocks are created when the magma has two distinct phases of cooling. [18] Igneous rocks are classified on the basis of texture and composition. Texture refers to the size, shape, and arrangement of the mineral grains or crystals of which the rock is composed. [citation needed]
Cumulate rock – Igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. Flow banding – Bands or layers that can sometimes be seen in rock that formed from magma; Fractional crystallization (chemistry) – Method for refining substances based on differences in their solubility
Partial melting is the phenomenon that occurs when a rock is subjected to temperatures high enough to cause certain minerals to melt, but not all of them. Partial melting is an important part of the formation of all igneous rocks and some metamorphic rocks (e.g., migmatites), as evidenced by a multitude of geochemical, geophysical and petrological studies.
A chilled margin is a shallow intrusive or volcanic rock texture characterised by a glassy or fine-grained zone along the margin where the magma or lava has contacted air, water, or particularly much cooler rock. This is caused by rapid solidification of the melt near the contact with the surrounding low temperature environment.
Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of magma or lava. Volcanism is the surface expression of magmatism.
Scoria or cinder is a pyroclastic, highly vesicular, dark-colored volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air to form discrete grains called clasts. [ 1 ] [ 2 ] It is typically dark in color (brown, black or purplish-red), and basaltic or andesitic in composition.