Full Answer
How is magma mixed in andesites?
Evidence of magma mixing is provided by the presence of phenocrysts in some andesites that are not in chemical equilibrium with the melt in which they are found. High-magnesium andesites ( boninites) in island arcs may be primitive andesites, generated from metasomatized mantle.
What is the composition of andesite and diorite?
Andesite and diorite have a composition that is intermediate between basalt and granite. This is because their parent magmas formed from the partial melting of a basaltic oceanic plate. This magma may have received a granitic contribution by melting granitic rocks as it ascended or mixed with granitic magma.
What is an andesitic rock?
Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Martian crust . The name andesite is derived from the Andes mountain range, where this rock type is found in abundance.
What is the temperature of andesitic magma?
It ranges in temperature from about 1000 oC to 1200 oC (1832 oF to 2192 oF). Andesitic magma has moderate amounts of these minerals, with a temperature range from about 800 oC to 1000 oC (1472 oF to 1832 oF).
How does magma affect the shape of a volcano?
What is the temperature of basaltic magma?
What is the name of the rock that erupts from the mantle?
What is the liquid rock that forms under the Earth's surface?
How does solid material turn into liquid?
Is magma a solid or a mixture?
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What is the composition of andesitic magma?
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende.
How does magma become andesitic?
Andesitic magma is formed through wet partial melting of the mantle. The mantle under the ocean has contact with water. When subduction, or continental plates pulling away from one another, occurs, the mantle will heat up and water is pushed into it.
What are the characteristics of andesitic magma?
Andesitic magma has moderate amounts of these minerals, with a temperature range from about 800oC to 1000oC (1472oF to 1832oF). Rhyolitic magma is high in potassium and sodium but low in iron, magnesium, and calcium. It occurs in the temperature range of about 650oC to 800oC (1202oF to 1472oF).
Where is andesitic magma formed?
convergent plate boundariesgeneration. Granitic, or rhyolitic, magmas and andesitic magmas are generated at convergent plate boundaries where the oceanic lithosphere (the outer layer of Earth composed of the crust and upper mantle) is subducted so that its edge is positioned below the edge of the continental plate or another oceanic plate.
How andesite is formed?
How was it formed? Andesite is a volcanic rock. It is fine-grained because it forms by the rapid cooling of magmas usually when it erupts onto the Earth's surface and forms lava flows. Andesite forms from magma that contains less quartz (silica) than rhyolite but more than basalt.
What is the characteristics of andesite?
Andesite is a dark, fine-grained, brown or greyish intermediate volcanic rock which is a commonly found in lava. The mineral composition of andesite includes biotite, pyroxene, or amphibole.
Does andesitic magma have high viscosity?
Andesitic magmas, in particular, have a wide range of magma viscosities, from 102 to 107 Pa s, which is due to a wide range in phenocryst contents from 0 (phenocryst‐free andesitic melt) to ∼50 vol % (50 vol % rhyolitic melt + 50 vol % phenocrysts).
How do you identify andesite?
0:071:20Identifying Andesite - YouTubeYouTubeStart of suggested clipEnd of suggested clipThis rock is andesite porphyry it's really stratovolcanoes it's erupted it's a volcanic rock. If youMoreThis rock is andesite porphyry it's really stratovolcanoes it's erupted it's a volcanic rock. If you look at the color scale it's an intermediate composition.
Which type of volcano is commonly composed of andesite?
Andesite (named after the Andes Mountains), is perhaps the most common rock type of stratovolcanoes, but stratovolcanoes also erupt a wide range of different rocks in different tectonic settings.
Where is andesite formed?
Andesite is a rock typically found in volcanoes above convergent plate boundaries between continental and oceanic plates.
What does the word andesite mean?
Definition of andesite : an extrusive usually dark grayish rock consisting essentially of oligoclase or feldspar.
Is andesitic magma high in silica?
Types of magma are determined by chemical composition of the magma. Three general types are recognized: Basaltic magma -- SiO2 45-55 wt%, high in Fe, Mg, Ca, low in K, Na. Andesitic magma -- SiO2 55-65 wt%, intermediate.
What process produces the most andesite volcanism?
Most of the explosive magma produced on Earth is produced by the process of subduction and is andesitic to rhyolitic in composition.
What is the difference between basaltic andesitic and rhyolitic magma?
Viscosity is most affected by temperature and silica content. There are three common types of magma which are as follows from high temperature to low temperature: basaltic (50% SiO2); andesitic (60% SiO2); and rhyolitic (70% SiO2). Basaltic magma has a low viscosity whereas rhyolitic magma has a high viscosity.
How is basaltic magma formed?
Basaltic magma is commonly produced by direct melting of the Earth's mantle, the region of the Earth below the outer crust. On continents, the mantle begins at depths of 30 to 50 km. Shield volcanoes, such as those that make up the Islands of Hawai'i, are composed almost entirely of basalt.
Is andesitic magma viscous?
Andesitic magmas, in particular, have a wide range of magma viscosities, from 102 to 107 Pa s, which is due to a wide range in phenocryst contents from 0 (phenocryst‐free andesitic melt) to ∼50 vol % (50 vol % rhyolitic melt + 50 vol % phenocrysts).
4 Different Types of Magma - Elist10
Simply put, magma is formed when solid rock and other constituents in the upper mantle or lower crust melts as the result of heat and pressure exerted upon them over a considerable length of time by a number of factors including ‘hotspots’, which are areas where the much hotter lower mantle effectively superheats the cooler material of the upper mantle and lower crust above and melts them.
magma | Components, Types, & Facts | Britannica
magma, molten or partially molten rock from which igneous rocks form. It usually consists of silicate liquid, although carbonate and sulfide melts occur as well. Magma migrates either at depth or to Earth’s surface and is ejected as lava. Suspended crystals and fragments of unmelted rock may be transported in the magma; dissolved volatiles may separate as bubbles and some liquid may ...
Magma Definition & Meaning - Merriam-Webster
The meaning of MAGMA is dregs, sediment. 3: molten rock material within the earth from which igneous rock results by cooling
What is high magnesium andesite?
High-magnesium andesites in island arcs may be primitive andesites, generated from metasomatized mantle. Experimental evidence shows that depleted mantle rock exposed to alkali fluids such as might be given off by a subducting slab generates magma resembling high-magnesium andesites.
What is the mineral composition of andesite?
However, it is often not possible to determine the mineral composition of volcanic rocks, due to their very fine grain size, and andesite is then defined chemically as volcanic rock with a content of 57% to 63% silica and not more than about 6% alkali metal oxides.
How does magma evolve?
Magmas in these reservoirs become evolved in composition (dacitic to rhyolitic) through both the process of fractional crystallization and partial melting of the surrounding country rock. Over time as crystallization continues and the system loses heat, these reservoirs cool. In order to remain active, magma chambers must have continued recharge of hot basaltic melt into the system. When this basaltic material mixes with the evolved rhyolitic magma, the composition is returned to andesite, its intermediate phase.
What is the extrusive equivalent of plutonic diorite?
Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, they are a major component of the Martian crust.
What happens to magma chambers when it mixes with rhyolitic magma?
When this basaltic material mixes with the evolved rhyolitic magma, the composition is returned to andesite, its intermediate phase.
What is the diameter of a andesite sample?
A sample of andesite (dark groundmass) with amygdaloidal vesicles filled with zeolite. Diameter of view is 8 cm.
What are some examples of accessory minerals?
Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals. Alkali feldspar may be present in minor amounts. Classification of andesites may be refined according to the most abundant phenocryst. Example: hornblende-phyric andesite, if hornblende is the principal accessory mineral.
What type of rock is Andesite?
Andesite is a fine-grained rock that forms when the magma erupts onto the surface and crystallizes quickly. Andesite and diorite have a composition that is intermediate between basalt and granite. This is because their parent magmas formed from the partial melting of a basaltic oceanic plate.
What are andesites crystals?
Occasionally, andesites contain large, visible grains of plagioclase, amphibole, or pyroxene. These large crystals are known as "phenocrysts." They begin forming when a magma, which is cooling at depth, approaches the crystallization temperature of some of its minerals. These high-crystallization-temperature minerals begin forming below the surface and grow to visible sizes before the magma erupts.
What is Andesite?
Andesite is the name of a family of fine-grained, extrusive igneous rocks that are usually light to dark gra y in color. They have a mineral composition that is intermediate between granite and basalt. Andesite is a rock typically found in volcanoes above convergent plate boundaries between continental and oceanic plates.
How does a volcano behave?
A volcano behaves in a similar manner. A rising magma chamber can instantly be depress urized by a landslide, faulting, or other event and an enormous volume of rapidly expanding gas will explode through the overlying rock. Many volcanic plumes and ash eruptions occur when gas-charged andesitic magmas erupt.
What is the name of the rock that forms when magma erupts?
This produces a rock with two different crystal sizes: large crystals that formed slowly at depth (the "phenocrysts"), and small crystals that formed quickly at the surface (known as "groundmass"). "Andesite porphyry" is the name used for these rocks ...
What is andesite porphyry?
There are many other environments where andesite might form. Hornblende Andesite Porphyry: A specimen of andesite with large visible hornblende phenocrysts. This type of rock could be called an "andesite porphyry" because of its texture. It could also be called a "hornblende andesite" because of its composition.
What is the difference between diorite and andesite?
Diorite is a coarse-grained igneous rock that forms when the magma remains below Earth's surface and cools slowly. Slow cooling facilitates the growth of large mineral crystals in the rock. Andesite is a fine-grained rock that forms when the magma erupts onto the surface and crystallizes quickly.
How does magma affect the shape of a volcano?
Both the temperature and mineral content of magma affect how easily it flows. The viscosity (thickness) of the magma that erupts from a volcano affects the shape of the volcano. Volcanoes with steep slopes tend to form from very viscous magma, while flatter volcanoes form from magma that flows easily. Lava (magma that has erupted onto the Earth's ...
What is the temperature of basaltic magma?
Basaltic magma is high in iron, magnesium, and calcium but low in potassium and sodium. It ranges in temperature from about 1000oC to 1200oC (18 32oF to 2192oF). Andesitic magma has moderate amounts of these minerals, with a temperature range from about 800oC to 1000oC (1472oF to 1832oF).
What is the name of the rock that erupts from the mantle?
Much of the planet’s mantle consists of magma. This magma can push through holes or cracks in the crust, causing a volcanic eruption. When magma flows or erupts onto Earth’s surface, it is called lava. Like solid rock, magma is a mixture of minerals. It also contains small amounts of dissolved gases such as water vapor, carbon dioxide, and sulfur.
What is the liquid rock that forms under the Earth's surface?
Magma . Magma is extremely hot liquid and semi-liquid rock located under Earth’s surface. Earth has a layered structure that consists of the inner core, outer core, mantle, and crust. Much of the planet’s mantle consists of magma. This magma can push through holes or cracks in the crust, causing a volcanic eruption.
How does solid material turn into liquid?
solid material turned to liquid by heat.
Is magma a solid or a mixture?
Like solid rock, magma is a mixture of minerals. It also contains small amounts of dissolved gases such as water vapor, carbon dioxide, and sulfur. The high temperatures and pressure under Earth’s crust keep magma in its fluid state.
Overview
Genesis
Intermediate volcanic rocks are created via several processes:
1. Fractional crystallization of a mafic parent magma.
2. Partial melting of crustal material.
3. Magma mixing between felsic rhyolitic and mafic basaltic magmas in a magma reservoir
Description
Andesite is an aphanitic (fine-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the feldspar in the rock consisting of plagioclase. This places andesite in the basalt/andesite field of the QAPF diagram. Andesite is further distinguished from basalt by its silica content o…
Andesitic volcanism
Andesite lava typically has a viscosity of 3.5 × 10 cP at 1,200 °C (2,190 °F). This is slightly greater than the viscosity of smooth peanut butter. As a result, andesitic volcanism is often explosive, forming tuffs and agglomerates. Andesite vents tend to build up composite volcanoes rather than the shield volcanoes characteristic of basalt, with its much lower viscosity resulting from its lower s…
Generation of melts in island arcs
Though andesite is common in other tectonic settings, it is particularly characteristic of convergent plate margins. Even before the Plate Tectonics Revolution, geologists had defined an andesite line in the western Pacific that separated basalt of the central Pacific from andesite further west. This coincides with the subduction zones at the western boundary of the Pacific Plate. Magmatism in island arc regions comes from the interplay of the subducting plate and the mantle …
Extraterrestrial samples
In 2009, researchers revealed that andesite was found in two meteorites (numbered GRA 06128 and GRA 06129) that were discovered in the Graves Nunataks icefield during the US Antarctic Search for Meteorites 2006/2007 field season. This possibly points to a new mechanism to generate andesite crust.
Along with basalts, andesites are a component of the Martian crust. The presence of distinctive …
See also
• List of rock types – List of rock types recognized by geologists
• Metamorphism – Change of minerals in pre-existing rocks without melting into liquid magma
• Oceanic crust – Uppermost layer of the oceanic portion of a tectonic plate
External links
• Origins of the Continental Crust, Abstract
• Origins of the Continental Crust, Full paper
• Island arc magmatism
• Experimental and Theoretical Constraints on Peridotite Partial Melting in the Mantle Wedge