Basalt

basalticcolumnar basaltpillow basaltbasaltspillow basaltsbasalt columnsbasaltic soilsbasaltic rockbasalt rockbasalt column
Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon.wikipedia
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Flood basalt

basaltbasalt floodbasalt flow
Flood basalt describes the formation in a series of lava basalt flows.
A flood basalt is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava.

Mafic

basicferromagnesianbasaltic lava
Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon.
Common mafic rocks include basalt, diabase and gabbro.

Andesite

andesiticadesiticandesidic
Due to weathering or high concentrations of plagioclase, some basalts can be quite light-coloured, superficially resembling andesite to untrained eyes.
In a general sense, it is the intermediate type between basalt and rhyolite, and ranges from 57 to 63% silicon dioxide (SiO 2 ) as illustrated in TAS diagrams.

Diabase

doleritedoleritesdolorite
The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarser) groundmass are generally referred to as diabase (also called dolerite) or, when more coarse-grained (crystals over 2 mm across), as gabbro.
Diabase or dolerite or microgabbro is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro.

Igneous rock

igneousigneous rocksdecompression melting
Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon.
Basalt is a common extrusive igneous rock and forms lava flows, lava sheets and lava plateaus.

Faroe Islands

FaroeseFaroesFaeroe Islands
It is the most common volcanic rock type on Earth, being a key component of oceanic crust as well as the principal volcanic rock in many mid-oceanic islands, including Iceland, the Faroe Islands, Réunion and the islands of Hawaiʻi.
The Faroe Islands are made up of a approximately 6 kilometers thick succession of mostly basaltic lava which was part of the great North Atlantic Igneous Province during the Paleogene period.

Scoria

reticulitescoriaceousVolcanic scoria
Basalt with a vesicular texture is called vesicular basalt, when the bulk of the rock is mostly solid; when the vesicles are over half the volume of a specimen, it is called scoria.
It is typically dark in color (generally dark brown, black or purplish red), and basaltic or andesitic in composition.

Igneous textures

aphanitictexture
Basalt is defined by its mineral content and texture, and physical descriptions without mineralogical context may be unreliable in some circumstances.
Examples of aphanitic igneous rock include basalt, andesite and rhyolite.

Iceland

IcelandicISLRepublic of Iceland
It is the most common volcanic rock type on Earth, being a key component of oceanic crust as well as the principal volcanic rock in many mid-oceanic islands, including Iceland, the Faroe Islands, Réunion and the islands of Hawaiʻi.
The island is composed primarily of basalt, a low-silica lava associated with effusive volcanism as has occurred also in Hawaii.

Volcanic rock

volcaniclava rockvolcanic rocks
More than 90% of all volcanic rock on Earth is basalt.
The initial composition of most volcanic rocks is basaltic, albeit small differences in initial compositions may result in multiple differentiation series.

Columbia River Basalt Group

Columbia River BasaltColumbia River basaltsColumbia River basalt flows
The basalt group includes the Steen and Picture Gorge basalt formations.

Komatiite

komatiiteskomatiitic
These ultramafic volcanic rocks, with silica (SiO 2 ) contents below 45% are usually classified as komatiites.
Basaltic lavas normally have eruption temperatures of about 1100 to 1250 °C.

Extrusive rock

extrusiveextrusionextruded
Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon.
If the magma contains abundant volatile components which are released as free gas, then it may cool with large or small vesicles (bubble-shaped cavities) such as in pumice, scoria, or vesicular basalt.

Ocean island basalt

OIBoceanic basaltsoceanic island basalts
Above sea level basalt is common in hotspot islands and around volcanic arcs, specially those on thin crust.
Ocean island basalt (OIB) is a volcanic rock, usually basaltic in composition, erupted in oceans away from tectonic plate boundaries.

Olivine

olivine basaltchrysoliteolivine group
These phenocrysts usually are of olivine or a calcium-rich plagioclase, which have the highest melting temperatures of the typical minerals that can crystallize from the melt.
That magma crystallizes to mafic rocks such as gabbro and basalt.

Oceanic crust

oceanicoceanic plateocean crust
It is the most common volcanic rock type on Earth, being a key component of oceanic crust as well as the principal volcanic rock in many mid-oceanic islands, including Iceland, the Faroe Islands, Réunion and the islands of Hawaiʻi.

Asthenosphere

asthenosphericasthenospheric mantleaesthenosphere
In the Hadean, Archean, and early Proterozoic eras of Earth's history, the chemistry of erupted magmas was significantly different from today's, due to immature crustal and asthenosphere differentiation.
It is considered the source region of mid-ocean ridge basalt (MORB).

Alkali basalt

alkali basaltsalkali olivine basaltalkaline
Alkali basalts typically have mineral assemblages that lack orthopyroxene but contain olivine.
Alkali basalt is characterized by relatively high alkali (Na 2 O and K 2 O) content relative to other basalts and by the presence of olivine and titanium-rich augite in its groundmass and phenocrysts, and nepheline in its CIPW norm.

Stolpen

Burg StolpenSchloßbergStolpen Castle
Agricola applied "basalt" to the volcanic black rock of the Schloßberg (local castle hill) at Stolpen, believing it to be the same as the "very hard stone" described by Pliny the Elder in Naturalis Historiae.
Schloßberg is a hill just to the south of the town formed of prominent basalt columns.

Porphyritic

porphyryporphyricPorphyritic texture
Basalt has a fine-grained mineral texture due to the molten rock cooling too quickly for large mineral crystals to grow; it is often porphyritic, containing larger crystals (phenocrysts) formed prior to the extrusion that brought the magma to the surface, embedded in a finer-grained matrix.
Porphyritic rocks may be aphanites or extrusive rock, with large crystals or phenocrysts floating in a fine-grained groundmass of non-visible crystals, as in a porphyritic basalt, or phanerites or intrusive rock, with individual crystals of the groundmass easily distinguished with the eye, but one group of crystals clearly much bigger than the rest, as in a porphyritic granite.

Phenocryst

phenocrystsphyricaphyric
Basalt has a fine-grained mineral texture due to the molten rock cooling too quickly for large mineral crystals to grow; it is often porphyritic, containing larger crystals (phenocrysts) formed prior to the extrusion that brought the magma to the surface, embedded in a finer-grained matrix.
Similarly, a basalt with olivine as the dominate phenocrysts, but with lesser amounts of plagioclase phenocrysts, might be termed a olivine-plagioclase phyric basalt.

Proterozoic

Proterozoic EonLate ProterozoicProterozoic Era
In the Hadean, Archean, and early Proterozoic eras of Earth's history, the chemistry of erupted magmas was significantly different from today's, due to immature crustal and asthenosphere differentiation.
As a result of remelting of basaltic oceanic crust due to subduction, the cores of the first continents grew large enough to withstand the crustal recycling processes.

Back-arc basin

back-arcback-arc spreadingback-arc extension
These ridges erupt basalts that are similar to those erupted from the mid-ocean ridges; the main difference is that back-arc basin basalts are often very rich in magmatic water (typically 1-1.5 weight % H 2 O), whereas mid-ocean ridge basalt magmas are very dry (typically

Volcanic glass

glassyglassbrownish glass
Basalt commonly features a very fine-grained or glassy matrix interspersed with visible mineral grains.

Phlogopite

fluorphlogopite micatetraferriphlogopite
Minerals such as alkali feldspar, leucite, nepheline, sodalite, phlogopite mica, and apatite may be present in the groundmass.
Several igneous associations are noted: high-alumina basalts, ultrapotassic igneous rocks, and ultramafic rocks.