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ShareVolcanic rock is an igneous rock of volcanic origin.
Volcanic rocks are usually fine-grained or aphanitic to glassy in texture.
They often contain clasts of other rocks and phenocrysts.
Phenocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye.
They were created during fractional crystallization of magma before extrusion.
Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a very fine grained matrix.
For more information about the topic Volcanic rock, read the full article at Wikipedia.org, or see the following related articles:
Igneous rock — Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive ... > read more
Pumice — Pumice is a highly vesicular pyroclastic igneous rock of intermediate to siliceous magmas including rhyolite, trachyte and phonolite. Pumice is ... > read more
Basalt rock — Basalt is a common gray to black volcanic rock. It is usually fine-grained due to rapid cooling of lava on the Earth's surface. It may be porphyritic ... > read more
Volcanic cone — Volcanic cones are among the simplest volcano formations. They are built by fragments (called ejecta) thrown up (ejected) from a volcanic vent, ... > read more
Volcanic ash — Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. Ash is created when ... > read more
Pyroclastic flow from volcanoes — Pyroclastic flows are a common and devastating result of some volcanic eruptions. They are fast-moving fluidized bodies of hot gas, ash and rock ... > read more
Caldera — A caldera is a volcanic feature formed by the collapse of a volcano into itself, making it a large, special form of volcanic crater. A caldera ... > read more
Metamorphic rock — Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means ... > read more
Stratovolcano — A stratovolcano is a tall, conical volcano composed of one layer of hardened lava, tephra, and volcanic ash. These volcanoes are characterized by a ... > read more
Supervolcano — A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruption on Earth. The actual explosivity of these ... > read more
Note: This page refers to an article that is licensed under the GNU Free Documentation License. It uses material from the article Volcanic rock at Wikipedia.org. See the Wikipedia copyright page for more details.
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