A report on Volcano and Igneous rock

Magma is the molten or semi-molten natural material from which all igneous rocks are formed.

Following its ascent through the crust, magma may feed a volcano and be extruded as lava, or it may solidify underground to form an intrusion, such as a dike, a sill, a laccolith, a pluton, or a batholith.

In geology, an igneous intrusion (or intrusive body or simply intrusion ) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth.

Volcanic necks are feeder pipes for volcanoes that have been exposed by erosion.

Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption.

Tuff can be classified as either igneous or sedimentary rock.

Carbonatite is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals.

Only one carbonatite volcano is known to have erupted in historical time, the active Ol Doinyo Lengai volcano in Tanzania.

Ignimbrites are igneous rocks made up of crystal and rock fragments in a glass-shard groundmass, albeit the original texture of the groundmass might be obliterated due to high degrees of welding.

Ignimbrite is the deposit of a pyroclastic density current, or pyroclastic flow, which is a hot suspension of particles and gases flowing rapidly from a volcano and driven by being denser than the surrounding atmosphere.

Usually, country rock is intruded by an igneous body of rock which formed when magma forced upward through fractures, or melted through overlying rock.

When describing recent alluvium, the material that has arrived through volcanic, glacial or fluvial action can be described as a veneer on the (older) country rock.

Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists.

Volcanoes near plate boundaries and mid-ocean ridges are built by the decompression melting of mantle rock that rises on an upwelling portion of a convection cell to the crustal surface.

Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content).

Volcanic ultramafic rocks are rare outside of the Archaean and are essentially restricted to the Neoproterozoic or earlier, although some boninite lavas currently erupted within back-arc basins (Manus Trough, New Guinea) verge on being ultramafic.

In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.

Felsite is a petrologic field term used to refer to very fine-grained or aphanitic, light-colored volcanic rocks which might be later reclassified after a more detailed microscopic or chemical analysis.