"kind of rock may thus be traced gradually merging into those of another. Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series. Igneous rock (derived from the Latin word ""igneus,"" meaning ""of fire,"" from ""ignis"" meaning ""fire)"" is formed through the cooling and solidification of magma or lava. This magma may be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in"
"rapidly it cools. Magma that reaches the surface to become lava cools rapidly, resulting in rocks with small crystals such as basalt. Some of this magma may cool extremely rapidly and will form volcanic glass (rocks without crystals) such as obsidian. Magma trapped below ground in thin intrusions cools more slowly than exposed magma and produces rocks with medium-sized crystals. Magma that remains trapped in large quantities below ground cools most slowly resulting in rocks with larger crystals, such as granite and gabbro. Existing rocks that come into contact with magma may be melted and assimilated into the magma. Other"
"known processes by which magma changes: by crystallization within the crust or mantle to form a pluton, or by volcanic eruption to become lava or tephra. When magma cools it begins to form solid mineral phases. Some of these settle at the bottom of the magma chamber forming cumulates that might form mafic layered intrusions. Magma that cools slowly within a magma chamber usually ends up forming bodies of plutonic rocks such as gabbro, diorite and granite, depending upon the composition of the magma. Alternatively, if the magma is erupted it forms volcanic rocks such as basalt, andesite and rhyolite"
"(the extrusive equivalents of gabbro, diorite and granite, respectively). During a volcanic eruption the magma that leaves the underground is called lava. Lava cools and solidifies relatively quickly compared to underground bodies of magma. This fast cooling does not allow crystals to grow large, and a part of the melt does not crystallize at all, becoming glass. Rocks largely composed of volcanic glass include obsidian, scoria and pumice. Before and during volcanic eruptions, volatiles such as CO and HO partially leave the melt through a process known as exsolution. Magma with low water content becomes increasingly viscous. If massive exsolution"
"and forming a denser conglomerate of minerals which sinks (cumulative rock). Upon cooling, new mineral phases saturate and the rock type changes (e.g. fractional crystallization), typically forming (1) gabbro, diorite, tonalite and granite or (2) gabbro, diorite, syenite and granite. If magma resides in a chamber for a long period, then it can become stratified with lower density components rising to the top and denser materials sinking. Rocks accumulate in layers, forming a layered intrusion. Any subsequent eruption may produce distinctly layered deposits; for example, the deposits from the 79 AD eruption of Mount Vesuvius include a thick layer of"
"sea floor beneath the American continental mass. As it sank, or subducted, beneath the western margin of the North American plate portions of the sea floor and overlying continental crust heated and melted, producing large molten masses (magma). Being lighter and hotter than the ancient continental crust above it, this magma forced its way upward, cooling as it rose to become the granite rock found throughout the Sierra Nevada and other mountains in California today. As the hot magma cooled, solidified, and came in contact with water, minerals with similar melting temperatures tended to concentrate together. As the magma solidified,"
"magmas, such as those that form rhyolite. Low viscosity leads to gentler, less explosive eruptions. Characteristics of several different magma types are as follows: Temperatures of most magmas are in the range 700 °C to 1300 °C (or 1300 °F to 2400 °F), but very rare carbonatite magmas may be as cool as 490 °C, and komatiite magmas may have been as hot as 1600 °C. At any given pressure and for any given composition of rock, a rise in temperature past the solidus will cause melting. Within the solid earth, the temperature of a rock is controlled by the"
"of magma that heats the surrounding rock causes contact metamorphism—a temperature-dominated transformation. Pressure metamorphism occurs when sediments are buried deep under the ground; pressure is dominant, and temperature plays a smaller role. This is termed burial metamorphism, and it can result in rocks such as jade. Where both heat and pressure play a role, the mechanism is termed regional metamorphism. This is typically found in mountain-building regions. Depending on the structure, metamorphic rocks are divided into two general categories. Those that possess a texture are referred to as foliated; the remainders are termed non-foliated. The name of the rock is"
"zones radiating from the summit. The type of lava erupted in this stage of activity is alkali basalt. Due to stretching forces, the development of two or more rift zones is common. The lava accumulates in a shallow magma storage reservoir. Because the eruptions occur with the volcano underwater, the form of lava typically erupted is pillow lava. Pillow lava is rounded balls of lava that was given very little time to cool due to immediate exposure to water. Water pressure prevents the lava from exploding upon contact with the cold ocean water, forcing it to simmer and solidify quickly."
"the lighter siliceous minerals such as aluminosilicates rise to the surface and form the crust, making up 0.4% of the Earth's mass. The crystallisation of igneous rocks from magma depends on a number of factors; among them are the chemical composition of the magma, the cooling rate, and some properties of the individual minerals to be formed, such as lattice energy, melting point, and complexity of their crystal structure. As magma is cooled, olivine appears first, followed by pyroxene, amphibole, biotite mica, orthoclase feldspar, muscovite mica, quartz, zeolites, and finally, hydrothermal minerals. This sequence shows a trend toward increasingly complex"
"as the magma flowed up the borehole, cooling into clear, colorless glass. The magma, at a temperature of approximately 1922°F (1050°C), was dacitic—similar to the granitic rock that forms continents—consisting of approximately two-thirds silica, which contrasts with the dark, iron-rich basaltic rock that forms most of the Hawaiian Islands. It was encountered after drilling through a layer of diorite igneous rock, which suggested to researchers that the magma had chemically separated as it dwelled for a long period of time. As quoted in the journal ""Nature"", the team said it was possibly the first time that ""the actual process of"
"of a planet, surrounded by pre-existing rock (called country rock); the magma cools slowly and, as a result, these rocks are coarse-grained. The mineral grains in such rocks can generally be identified with the naked eye. Intrusive rocks can also be classified according to the shape and size of the intrusive body and its relation to the other formations into which it intrudes. Typical intrusive formations are batholiths, stocks, laccoliths, sills and dikes. When the magma solidifies within the earth's crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, or diorite. The central cores of major mountain"
"form above the ring fracture. As the magma chamber empties, the center of the volcano within the ring fracture begins to collapse. The collapse may occur as the result of a single cataclysmic eruption, or it may occur in stages as the result of a series of eruptions. The total area that collapses may be hundreds or thousands of square kilometers. Some calderas are known to host rich ore deposits. One of the world's best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario, Canada, which formed during the Neoarchean era about 2,700 million years ago. If the magma"
"frozen in place as the rock cools and solidifies. Scoria may form as part of a lava flow, typically near its surface, or as fragmental ejecta (lapilli, blocks and bombs), for instance in Strombolian eruptions that form steep-sided scoria cones. Most scoria is composed of glassy fragments, and may contain phenocrysts. The word ""scoria"" comes from the Greek σκωρία, ""skōria"", rust. A colloquial term for scoria is cinder. Scoria differs from pumice, another vesicular volcanic rock, in having larger vesicles and thicker vesicle walls, and hence is denser. The difference is probably the result of lower magma viscosity, allowing rapid"
"rocks may display some degree of porphyritic texture. One main type of rock that has a porphyritic texture are porphyry, though not all porphyritic rocks are porphyries. Porphyritic rocks are formed when a column of rising magma is cooled in two stages. In the first stage, the magma is cooled slowly deep in the crust, creating the large crystal grains, with a diameter of 2 mm or more. In the final stage, the magma is cooled rapidly at relatively shallow depth or as it erupts from a volcano, creating small grains that are usually invisible to the unaided eye typically"
"Cryovolcano A cryovolcano (sometimes informally called an ice volcano) is a type of volcano that erupts volatiles such as water, ammonia or methane, instead of molten rock. Collectively referred to as cryomagma, cryolava or ice-volcanic melt, these substances are usually liquids and can form plumes, but can also be in vapour form. After eruption, cryomagma is expected to condense to a solid form when exposed to the very low surrounding temperature. Cryovolcanoes may potentially form on icy moons and other objects with abundant water past the Solar System's snow line (such as Pluto). A number of features have been identified"
"volatile diffusion, bubble growth, coalescence, and bursting. As rising magma encounters lower pressures, dissolved gases are able to exsolve and form vesicles. Some of the vesicles are trapped when the magma chills and solidifies. Vesicles are usually small, spheroidal and do not impinge upon one another; instead they open into one another with little distortion. Volcanic cones of scoria can be left behind after eruptions, usually forming mountains with a crater at the summit. An example is Maungarei in New Zealand, which like Te Tatua-a-Riukiuta in the south of the same city has been extensively quarried. Quincan, a unique form"
"barrier to the re-release of CO into the atmosphere. Basalt 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. More than 90% of all volcanic rock on Earth is basalt. Basalt lava has a low viscosity, due to its low silica content, resulting in rapid lava flows that can spread over great areas before cooling and solidification. Flood basalt describes the formation in a series of lava basalt flows. By definition, basalt is an aphanitic (fine-grained)"
"cooling liquid magma, and subsequently solidified on or near the atmosphere (volcanic or extrusive). These are found at the mid-western portion of the municipality (Dupinga) as well as on the south-eastern boundary of San Luis with the municipality of Dingalan. These rocks are composed of basalt, andesite, greywackes and breccia. Metamorphic rocks are altered rocks from sedimentary and igneous origin and are formed due to intense pressure and temperature. Their composition includes amphibolites, quartz feldspar, Phyllites and slate. Metamorphic rocks are largely found at the western and eastern portion of the municipality (mountainous areas facing the Pacific Ocean). Four (4)"
"a primitive melt, and identifying whether the magma has dropped out cumulate minerals is equally important even for rocks which carry no phenocrysts. The primary cause of change in the composition of a magma is ""cooling"", which is an inevitable consequence of the magma being created and migrating from the site of partial melting into an area of lower stress - generally a cooler volume of the crust. Cooling causes the magma to begin to crystallize minerals from the melt or liquid portion of the magma. Most magmas are a mixture of liquid rock (melt) and minerals (phenocrysts). Contamination is"
"or without suspended crystals and gas bubbles, is called magma. It rises because it is less dense than the rock from which it was created. When magma reaches the surface from beneath water or air, it is called lava. Eruptions of volcanoes into air are termed ""subaerial"", whereas those occurring underneath the ocean are termed ""submarine"". Black smokers and mid-ocean ridge basalt are examples of submarine volcanic activity. The volume of extrusive rock erupted annually by volcanoes varies with plate tectonic setting. Extrusive rock is produced in the following proportions: Magma that erupts from a volcano behaves according to its"
"forming a lobe, until the pressure of the magma becomes sufficient to rupture the skin and start the formation of a new eruption point nearer the vent. This process produces a series of interconnecting lobate shapes that are pillow-like in cross-section. The skin cools much faster than the inside of the pillow, so it is very fine-grained, with a glassy texture. The magma inside the pillow cools slowly, so is slightly coarser grained than the skin, but nevertheless it is still classified as fine grained. Pillow lavas can be used as a way-up indicator in geology; that is, study of"
"in a rock under pressure can stabilize a melt fraction. The presence of even 0.8% water may reduce the temperature of melting by as much as 100 °C. Conversely, the loss of water and volatiles from a magma may cause it to essentially freeze or solidify. Also a major portion of almost all magma is silica, which is a compound of silicon and oxygen. Magma also contains gases, which expand as the magma rises. Magma that is high in silica resists flowing, so expanding gases are trapped in it. Pressure builds up until the gases blast out in a violent,"
"veins. Ore minerals, including the incompatible elements, remain dissolved in the hot solution, then crystallize out when the solution cools. Deposits created by means of these hot solutions are called hydrothermal deposits. Some of the world's most significant deposits of gold, silver, lead, mercury, zinc, and tungsten started out this way. Nearly all the mines in the northern Black Hills of South Dakota came to be because of hot water deposits of minerals. Cracks often form when a mass of magma cools because magma contracts and hardens when it cools. Cracks occur both in the frozen magma mass and in"
"gas bubbles. If the magma is rising slowly enough, these bubbles will have time to rise and escape, leaving a less buoyant magma behind that fluidly flows out. Effusive basalt lava flows cool to either of two forms, ʻaʻā (pronounced “ah ah”) or pāhoehoe (pronounced “puh hoy hoy”). This type of lava flow builds shield volcanoes, which are numerous in Hawaii, and is how the island was and currently is being formed. Silicic magmas most commonly erupt explosively, but they can erupt effusively. These magmas are water saturated, and many orders of magnitude more viscous than basaltic magmas, making degassing"
"crystallized slowly below Earth's surface. As magma cools slowly the minerals have time to grow and form large crystals. The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye. Examples of phaneritic igneous rocks are gabbro, diorite and granite. ""Porphyritic"" textures develop when conditions during cooling of a magma change relatively quickly. The earlier formed minerals will have formed slowly and remain as large crystals, whereas, sudden cooling causes the rapid crystallization of the remainder of the melt into a fine grained (aphanitic) matrix. The result is an aphanitic rock with"
"the southern margin of the Tibetan Plateau. Granite and rhyolite are types of igneous rock commonly interpreted as products of the melting of continental crust because of increases in temperature. Temperature increases also may contribute to the melting of lithosphere dragged down in a subduction zone. Most magmas only entirely melt for small parts of their histories. More typically, they are mixes of melt and crystals, and sometimes also of gas bubbles. Melt, crystals, and bubbles usually have different densities, and so they can separate as magmas evolve. As magma cools, minerals typically crystallize from the melt at different temperatures"
"Basalt 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. More than 90% of all volcanic rock on Earth is basalt. Basalt lava has a low viscosity, due to its low silica content, resulting in rapid lava flows that can spread over great areas before cooling and solidification. Flood basalt describes the formation in a series of lava basalt flows. By definition, basalt is an aphanitic (fine-grained) igneous rock with generally 45–53% silica (SiO) and less"
"rock from the Earth's core, producing projectiles composed of lava, or miniature volcanoes. When using her powers, Magma typically assumes an energized form that emits intense light and heat. She can also create orbs of a fire-like substance and use them as projectiles or a source of light. Although Magma has triggered small earth tremors without taking on her energized form, she has never been seen to use her power to control lava while in her ordinary human appearance. On M-Day, she traveled within the heated gases of an active volcano, and demonstrates an immunity to volcanic gases, heat, and"
"magma forms by partial melting of silicate rocks either in the mantle, continental or oceanic crust. Evidence for magmatic activity is usually found in the form of igneous rocks – rocks that have formed from magma. Magmatism is associated with all stages of the development of convergent plate boundaries, from the initiation of subduction through to continental collision and its immediate aftermath. The subduction of oceanic crust, whether beneath oceanic of continental crust, is associated in almost all cases with partial melting of the overlying asthenosphere due to the addition of volatiles (especially water) expelled from the downgoing slab. Only"
"two classes: Volcanic pyroclastic rocks are formed by explosive eruption of lava and any rocks which are entrained within the eruptive column. This may include rocks plucked off the wall of the magma conduit, or physically picked up by the ensuing pyroclastic surge. Lavas, especially rhyolite and dacite flows, tend to form clastic volcanic rocks by a process known as ""autobrecciation"". This occurs when the thick, nearly solid lava breaks up into blocks and these blocks are then reincorporated into the lava flow again and mixed in with the remaining liquid magma. The resulting breccia is uniform in rock type"
"In modern times, the apron of material around the volcano's main vent extends at least from its source in places that were covered by ice. In other areas its extent is less and its slope is steeper. Stratovolcanoes are a common feature of subduction zones. The magma that forms them arises when water, which is trapped both in hydrated minerals and in the porous basalt rock of the upper oceanic crust, is released into mantle rock of the asthenosphere above the sinking oceanic slab. The release of water from hydrated minerals is termed ""dewatering"", and occurs at specific pressure/temperature conditions"
"downwards before the magma becomes completely solid, allowing concentration of rare elements to proceed so far that they produce their own distinctive minerals. The resulting rock is igneous in appearance but formed at a low temperature from a water-rich melt, with large crystals of the common minerals such as quartz and feldspar, but also with elevated concentrations of rare elements such as beryllium, lithium, or niobium, often forming their own minerals; this is called a pegmatite. The high water content of the magma made it possible for the crystals to grow quickly, so pegmatite crystals are often quite large, which"