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Topic: Igneous rock

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In the News (Thu 18 Apr 19)

  Igneous Rock Identification Exercise
Igneous rocks are crystalline or glassy rocks formed by the cooling and solidification of molten magma.
Rocks formed from the cooling and solidification of magma deep within the crust are distinct from those erupted at the surface mainly owing to the differences in conditions in the two environments.
As discussed earlier, texture is used to subdivide igneous rocks into two major groups: (1) the plutonic rocks, with mineral grain sizes that are visible to the naked eye, and (2) the volcanic types, which are usually too fine-grained or glassy for their mineral composition to be observed without the use of a microscope.
geology.csupomona.edu /alert/igneous/ignrxs.htm   (1238 words)

  ScienceDaily: Igneous rock   (Site not responding. Last check: 2007-11-02)
Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.
Igneous rock -- Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive...
Sedimentary rock -- Sedimentary rock is one of the three main rock groups (along with igneous and metamorphic rocks) and is formed in four main ways: by the deposition of the weathered remains of other rocks (known as...
www.sciencedaily.com /encyclopedia/Igneous_rock   (1460 words)

  CVO Website - Igneous Rocks
Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies.
Igneous rocks are classified by the geologic environment where they formed from the crystallization of molten material, and perhaps more importantly, by their mineral composition.
Rocks of intermediate composition are derived from the mixing of continental and oceanic crust.
vulcan.wr.usgs.gov /LivingWith/VolcanicPast/Notes/igneous_rocks.html   (852 words)

  Igneous rock - Wikipedia, the free encyclopedia
Oceanic crust is composed primarily of basalt, gabbro and peridotite.
Igneous rocks make up approximately ninety five percent of the upper part of the Earth's crust, but their great abundance is hidden on the Earth's surface by a relatively thin but widespread layer of sedimentary and metamorphic rocks.
Igneous rock are classified according to mode of occurrence, texture, chemical composition, and the geometry of the igneous body.
en.wikipedia.org /wiki/Igneous_rock   (1948 words)

 Igneous rock - Wikipedia, the free encyclopedia
Most of the magma which forms igneous rocks is generated within the upper parts of the mantle at temperatures estimated between 600 to 1600 °C. As magma cools, minerals crystallize from the melt at different temperatures (fractional crystallization).
Igneous rocks are classified according to mode of occurrence, texture, chemical composition, and the geometry of the igneous body.
Extrusive igneous rocks (also called volcanic rocks, named after Vulcan, the Roman name for the god of fire) are formed at the Earth's surface as a result of volcanic activity.
www.hoover.us /project/wikipedia/index.php/Volcanic_rock   (1513 words)

 igneous rock - Hutchinson encyclopedia article about igneous rock   (Site not responding. Last check: 2007-11-02)
Granite is an igneous rock, normally found deep in the earth's crust and made of crystals formed from the cooling of molten magma.
Rock formed from the cooling and solidification of molten rock called magma.
The acidic nature of this rock type means that areas with underlying igneous rock are particularly susceptible to the effects of acid rain.
encyclopedia.farlex.com /igneous%20rock   (296 words)

 Rock (geology) - Wikipedia, the free encyclopedia
Rocks are classified by mineral and chemical composition; the texture of the constituent particles; and also by the processes that formed them.
Igneous rocks are formed from molten magma and are divided into two main categories: plutonic rock and volcanic rock.
Plutonic or intrusive rocks result when magma cools and crystallises slowly within the Earth's crust, while volcanic or extrusive rocks result from magma reaching the surface either as lava (when the molten rock is in the mantle, it is called magma, when it is above the crust, it is called lava) or fragmental ejecta.
en.wikipedia.org /wiki/Rock_(geology)   (324 words)

 Amateur Geologist Structured Geological Glossary: Igneous Rocks
Igneous rock that is interpreted as a former intrusion from its cross-cutting contacts, chilled margins, or other field relations.
The unsorted, angular, and un-rounded texture of the fragments in a pyroclastic rock.
An igneous rock texture in which the mineral grain are large enough to be seen with the unaided eye and are of approximately equal size.
www.amateurgeologist.com /content/glossary/rock/igneous.html   (4089 words)

 Igneous Rock - MSN Encarta
Igneous rocks are one of the three main types of rocks; the other types are sedimentary rocks and metamorphic rocks.
Igneous rocks may also be classified according to the minerals they contain.
Rocks formed within the earth are called intrusive or plutonic rocks because the magma from which they form often intrudes into the neighboring rock.
encarta.msn.com /encyclopedia_761555655/igneous_rocks.html   (588 words)

 How Igneous Rocks Are Formed   (Site not responding. Last check: 2007-11-02)
Igneous rocks are called fire rocks and are formed either underground or above ground.
Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets.
Igneous rocks are formed as the lava cools above ground.
sln.fi.edu /fellows/payton/rocks/create/igneous.htm   (93 words)

 Introduction to Igneous Rocks
Igneous rocks are classified in several different ways (link), but all rock classifications are a combination of texture and color/composition of the rock.
A final outcome of all this is that different igneous rocks are found in different places on the earth, and all these different distributions are related to plate tectonic processes, and to the history of the earth.
At its simplest, continents are made of felsic igneous rocks (such as granite), ocean basins made of mafic igneous rocks (such as basalt and gabbro), and volcanic arcs of intermediate igneous rocks (such as diorite and andesite.)
csmres.jmu.edu /geollab/Fichter/IgnRx/Introigrx.html   (1420 words)

 Earth Floor: Cycles
Igneous rock can change into sedimentary rock or into metamorphic rock.
Igneous rock forms when magma cools and makes crystals.
Igneous rock can form underground, where the magma cools slowly.
www.cotf.edu /ete/modules/msese/earthsysflr/rock.html   (365 words)

 Igneous Rock: Face of the Earth   (Site not responding. Last check: 2007-11-02)
Igneous rock is rock formed by the hardening and crystallization of molten material that originates deep within the earth.
Rocks that have hardened from magma, the hot liquid beneath the earth's crust, are called igneous rocks.
Extrusive rocks form when magma flows onto the surface of the earth or floor of the ocean through deep cracks or fissures and at volcanic vents, and then cools and hardens.
www.edu.pe.ca /southernkings/igneousjj.htm   (311 words)

 Classification of Igneous Rocks - flow chart   (Site not responding. Last check: 2007-11-02)
One criticism of the IUGS classification of rocks, discussed by Le Bas and Streckeisen (1991), is that it is deficient in a strong genetic component.
Lamprophyres are mesocratic to melanocratic igneous rocks, usually hypabyssal, with a panidiomorphic texture and abundant mafic phenocrysts of dark mica or amphibole (or both) with or without pyroxene, with or without olivine, set in a matrix of the same minerals, and with feldspar (usually alkali feldspar) restricted to the groundmass.
Rocks falling in the shaded areas of the triangular diagrams may be further subdivided according to the diagram within the shaded rectangle.
www.geol.lsu.edu /henry/Geology3041/lectures/02IgneousClassify/IUGS-IgneousClassFlowChart.htm   (10379 words)

 Igneous rock
Igneous rocks are formed when molten rock (magma derived from the Earth's mantle, or, pre-existing rocks molten by extreme temperature) cools and solidifies, with or without crystallization.
The most important distinction in igneous rocks is texture, which is related to the size and shape of the constituent crystallite gains.
Granite is an igneous, intrusive rock (crystallyzed at depth), with felsic acid composition (rich in silica and with more than 10% of felsic minerals) and phaneritic, subeuedral texture (minerals are visible for the unaided eye and some of them retain original crystallographic shapes).
www.knowledgefun.com /book/i/ig/igneous_rock.html   (630 words)

 Igneous Rocks
Igneous rocks get their name from the Latin word ignis, meaning "fire." Small wonder: the magma from which igneous rocks form can reach temperatures close to 1200°C (2192°F).
Igneous rocks are formed by solidification of magma -- a complex melt in the earth's crust.
Igneous rocks are formed from molten magma or lava.
www.cdli.ca /CITE/rocks_igneous.htm   (441 words)

 The 3 basic rock types   (Site not responding. Last check: 2007-11-02)
Igneous rocks are crystalline solids which form directly from the cooling of magma.
Igneous rocks are given names based upon two things: composition (what they are made of) and texture (how big the crystals are).
In most places on the surface, the igneous rocks which make up the majority of the crust are covered by a thin veneer of loose sediment, and the rock which is made as layers of this debris get compacted and cemented together.
jersey.uoregon.edu /~mstrick/AskGeoMan/geoQuerry13.html   (484 words)

 10(e) Characteristics of Igneous Rocks
The type of igneous rocks that form from magma is a function of three factors: the chemical composition of the magma; temperature of solidification; and the rate of cooling which influences the crystallization process.
Rocks that begin their cooling at low temperatures tend to be rich in minerals composed of silicon, potassium, and aluminum.
Mafic igneous rocks tend to be dark in color because they contain a large proportion of minerals rich in iron and magnesium (pyroxene, amphiboles, and olivine).
www.physicalgeography.net /fundamentals/10e.html   (1097 words)

 Petrology - Igneous Rock
Igneous rock has played a major role in Earth's crustal evolution and is the precursor of sedimentary and metamorphic rock (Raymond, 1995, p.
Igneous rocks are named and classified based on texture and mineral make-up, and color provides a measure for estimating the general mineral compositions.
Igneous rock with a carbonate mineral assemblage, primarily calcite, is not common, but may occur in carbonatite.
www.emporia.edu /earthsci/amber/go240/igneous.htm   (1078 words)

 USGS Learning Web :: Explorers :: Rocks and Images
Igneous rocks, also called volcanic rocks, are formed from melted rock that has cooled and solidified.
When rocks are buried deep within the Earth, they melt because of the high pressure and temperature; the molten rock (called magma) can then flow upward or even be erupted from a volcano onto the Earth's surface.
Igneous rocks cooled beneath the Earth's surface are called intrusive rocks.
interactive2.usgs.gov /learningweb/explorer/topic_rocks_igneous.htm   (213 words)

 Igneous Rock Texture
Aphanitic rock is igneous rock in which the grain or crystalline structure is too fine to be seen by the unaided eye.
Phaneritic rock is igneous rock with large, identifiable crystals of roughly equal size.
Porphyritic rock is igneous rock which is characterized by large crystals surrounded by a background of material with very small crystals.
hyperphysics.phy-astr.gsu.edu /hbase/geophys/texture.html   (421 words)

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