This type of rock may have crystals, air bubbles or a glassy surface. The magma can be derived from partial melts of existing rocks in either a planets mantle or crust. Igneous textures the texture of a rock is a result of various processes that controlled the rock s genesis and, along with mineralogy and chemical composition, provides information that we may use to interpret the rock s origin and history table 3. Classification of igneous rocks gill 2010 chemical composition. This worksheet has 14 earth science regents questions about igneous rocks. Plutonic bodies with different dimensions and geometry form.
Pdf chemical composition of igneous rocks and origin of the sill. There are both multiple choice and fillin questions. Because of the dominance of oxygen and silicon in the crust, igneous rocks are mostly made up of silicate minerals. Igneous rock evolution plate tectonics and igneous rock distribution. You may also want to refer to barker, 1983, pages 106120. The felsic minerals include quartz, tridymite, cristobalite, feldspars plagioclase and alkali feldspar, feldspathoids nepheline and leucite, muscovite, and corundum. Igneous rocks with low silica content and very high levels of magnesium and iron. Ternary classification of felsic to mafic igneous rocks. Intrusive rocks become exposed on the earths surface when overlying material is eroded away. Note that rocks with glassy or pyroclastic textures may be described by the above compositions, but that for these specimens the final rock name must still. From the pictures pupils should identify some trends eg. These minerals are high in magnesium and ferric oxides, and their presence gives mafic rock its characteristic dark colour. Show pupils some igneous rocks, stress which ones they should be able to name later as examples.
Describe the process of igneous evolution and the role of 7. Identify how igneous rock color relates to chemical 5. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Chemical composition of igneous rocks and origin of the sill and pillowbasalt complex of nauru basin, southwest pacific. The igneous rocks are those which have solidified from a molten condition.
Apr 16, 2014 general characteristics of magma igneous rocks form as molten rock cools and solidifies general characteristics of magma parent material of igneous rocks forms from partial melting of rocks magma at surface is called lava rocks formed from lava extrusive, or volcanic rocks rocks formed from magma at depth intrusive, or plutonic rocks the. Lecture notes 3 igneous rocks glendale community college. The major mineralogical components of igneous rocks can be divided into two groups. Mafic rock, in geology, igneous rock that is dominated by the silicates pyroxene, amphibole, olivine, and mica. Rocks formed from lava are extrusive, or volcanic rocks. An introduction to igneous and metamorphic petrology, john winter, prentice hall. Igneous rocks and processes city university of new york. Forms and structures of igneous rocks springerlink. We have recently completed computations of the average chemical composition of the igneous rocks of various countries, of the.
Contain 10% dark silicate minerals like biotite mica and amphibule. Occurrence, texture, and classification of igneous rocks. By comparison of their characters with those of certain igneous rocks intercalated in the geological column, it can be shown that the latter are the lavas of. Igneous rocks are the oldest type of rock and is a volcanic rock. Chemical composition of igneous rocks and origin of the sill and pillowbasalt complex of nauru basin, southwest pacific article pdf available august 1981 with 464 reads how we measure reads. Earth, forms one of the most common igneous rocks, granite.
Igneous rocks igneous rocks form by cooling and crystallization of molten rock molten material residing below earths surface is known as magma, whereas the same material at the surface is called lava. Introduction rock is defined as a mixtures formed of aggregates of one or more minerals aggregate of minerals. You will also definitely want to look at mackenzie et al. Characteristics of igneous rocks most igneous rocks are very hard made of crystals layering is not common in igneous rocks metamorphic rocks sedimentary and igneous rocks can become buried deep in the earths crust. Igneous rock identification university of washington. Some cool thus quickly that they type an amorphous glass. Explain the difference between intrusive and extrusive igneous rocks. Youll also find a handson activity to try at home or at school, as well as a glossary of unfamiliar words, resources to help you locate additional information, and a useful index. Typical occurrences of igneous rock bodies on the surface include lava flows, lava domes, necks and spines. Igneous rock derived from the latin word ignis meaning fire, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic.
Intrusive igneous rocks cool slowly and form very large crystals. Igneous rocks are classified according to their texture and composition. Intrusive igneous rocks form when the magma cools slowly under the earths surface. Igneous rocks originated through solidification of molten material either at or below the surface. Igneous rock texture igneous rocks are commonly classified by their composition and texture. Ultramafic rocks are dominated by olivine andor pyroxene mafic rocks are dominated by plagioclase and pyroxene even if you cant see them with the naked eye and smaller amounts of olivine. Read igneous rocks to find the answers to these questions and many more. Questions relate to using the earth science reference tables page 6 scheme for igneous rocks, environment of formation extrusive vs. May 14, 2017 learning objectives be able to name some igneous rocks be able to describe how igneous rocks are formed. Pictures and brief descriptions of some common igneous rock types are shown on this page. Igneous rocks formed of cooled lava or volcanic ejecta are common, but most molten material cools below earths surface. Chemical composition of igneous rocks expressed by means of.
Extrusive igneous rocks tend to cool much more rapidly, and the minerals grow quicker and can not get as large. Petrography the branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. Igneous rocks are formed when magma cools, either on earths surface or beneath it, though some may form by fragmentation of solidifying magma. Typical occurrences of igneous rock bodies on the surface include lava flows, lava domes, necks and spines, and pyroclastic deposits. For instance, the name of a coarse grained intrusive igneous rock with a felsic composition is granite whereas the name. An igneous texture consisting of large crystals embedded in a matrix of much smaller crystals. Intermediate compositions lie between these two end members. The most obvious and unequivocal examples are the lavas which have been poured out from presentday volcanoes. Igneous rocks and processes revised on 102011 page 5 of 10 finegrained or aphanitic. Magmas and igneous rocks magma and igneous rocks igneous rocks are formed by crystallization from a liquid, or magma. When the molten rock magma cools and solidifies before it reaches the surface it forms intrusive igneous rock.
It comes from deep in the earth where magma is formed. Identify the information revealed by igneous texture 4. Because igneous rocks form under diverse conditions, they differ widely in texture, mineral composition, and appearance. Igneous rock is formed through the cooling and solidification of magma or lava. In contrast, extrusive igneous rocks are formed outside the earths crust, when lava cools. A quick introduction to igneous rocks including the ways in which they form and their identifiable physical characteristics like inter grown crystals and vesicular gas pockets. This will lead us into discussions on magma, silicate minerals, and the construction of a useful illustration that may be used to both name an igneous rock and determine its mineral content. A coarsegrained intermediate igneous rock with a composition between that of granodiorite and that of gabbro. A magma consists mostly of liquid rock matter, but may contain crystals of various minerals, and may contain a gas phase that may be dissolved in the liquid or may be present as a separate gas phase. Parent material of igneous rocks forms from partial melting of rocks magma at surface is called lava general characteristics of magma general characteristics of magma.
The classification and nomenclature of igneous rocks are treated in the final section. The sio 2 may occur as free quartz or be combined with varying proportions of elements to form minerals such as feldspar. Igneous rocks form as molten rock cools and solidifies general characteristics of magma. Composition of igneous rocks reflects the chemistry of the original magma. To simplify the discussion we are severely reducing the number of igneous rocks you need to know to an essential few. From the pictures pupils should identify some trends eg crystals and colour. Most are composed of the eight most abundant elements in the earths crust. Igneous rocks that crystallize slowly beneath the earth s surface, typically have visible individual minerals. Pdf chemical composition of igneous rocks and origin of the. The top diagram is for extrusive rocks and the lower is for intrusive rocks. An introduction to igneous rocks requires exploration of three core ideas. Feb 18, 2015 introduction to the formation of igneous rocks, including, extrusive and intrusive rocks. When the magma reaches the earths surface and turns into lava, it cools and turns into igneous rock. Principles of igneous and metamorphic petrology second.
Igneous rocks are formed when rocks are melted and then cooled again. To identify rocks, you must not be shy about taking a hand lens to carefully examine a rock before announcing its identity. These silicates can be generally divided into light and dark silicates. Norman bowen 18871956 father of experimental petrology. If it crystallizes before it reaches the surface it will form an igneous rock at depth called a plutonic or intrusive igneous rock. Hydrothermal activity spatially associated with ultramafic rocks, usually serpentinites, has been observed at several localities proximal.
In practice, this means that the average dimension of the crystals is less than 1 millimeter. These rocks embody andesite, basalt, obsidian, pumice, rhyolite, scoria, and tuff. Texture is the term applied to the overall appearance of a rock based on the size, shape, and arrangement of the interlocking mineral crystals which form it. Classification of igneous rocks streckheisen classification is based on only three minerals. Teacher notes if your students have completed the plate tectonic units on volcanoes, they should be familiar with different volcanic environments. Samples of intrusive igneous rocks are igneous rock, gabbro, granite, pegmatite, and peridotite. Introduction to the formation of igneous rocks, including, extrusive and intrusive rocks. Introduction to igneous rocks an igneous rock is any crystalline or glassy rock that forms from cooling of a magma. Molten rock inside the earth is called magma, while molten rock on the earths surface is called lava. Igneous rocks formed of cooled lava or volcanic ejecta are common, but most molten material cools below.
General characteristics of magma igneous rocks form as molten rock cools and solidifies general characteristics of magma parent material of igneous rocks forms from partial melting of rocks magma at surface is called lava rocks formed from lava extrusive, or volcanic rocks rocks formed from magma at depth intrusive, or plutonic rocks the. Metamorphic rocks form when the buried rock is changed under high temperature and pressure. Types of magma chemical composition of magma is controlled by the abundance of elements in the earth. Igneous rocks comprise such types as the common granites which formed from tremendously large masses of molten material intruded from depths of the earth into the crust, then 1. Glg 333 igneous textures and structures the following is a reorganization and amplification of blatt and tracy, 1996, pages 3944. In the modern oceans, the mafic association is found in two specific settings. Igneous rocks are classified by texture and chemical composition.
Ultramafic rocks are dominated by olivine andor pyroxene mafic rocks are dominated by plagioclase and pyroxene even if you cant see them with the naked eye and smaller amounts of olivine intermediate rocks are roughly even mixtures of felsic minerals mainly plagioclase and mafic minerals mainly hornblende. Since oxygen is so abundant, chemical analyses are usually. Characteristics of sedimentary rocks often contain layers look for grains in the rock igneous rocks igneous rocks come from the cooling of melted rock material, called magma. Igneous rocks are classified according to their mineral content. Igneous rocks are formed when molten rock magma cools and solidifies, with or without crystallization, either below the surface as intrusive plutonic rocks. Formation, classification, and identification of igneous rocks next. Mafic rock is commonly contrasted with felsic rock, in which. Extrusive igneous rocks erupt onto the surface, wherever they cool quickly to make little crystals.
Learning objectives be able to name some igneous rocks be able to describe how igneous rocks are formed. Igneous rock igneous rock mineralogical components. Intrusive igneous rocks form inside the earth, when magma cools. The processes that lead to the formation of igneous rocks have brought earths water to the surface as well as the atmosphere and the chemicals that make up all of organic life, produced most of its metallic ore. The table below shows classification of major groups of igneous rocks based on their mineral composition and texture.
They include two types zvolcanic or extrusive igneous rocks form when the magma cools and crystallizes on the surface of the earth zintrusive or plutonic igneous rocks wherein the magma crystallizes at depth in the earth. This reader emphasizes how all igneous rocks are formed and explores how the formation is related to igneous rock classification. These rocks include andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff. Each of these is introduced simplistically below, and then further explored in other pages of the site. Contain 70% silica and are major rocks of the continental shelf.
Principles of igneous and metamorphic petrology second edition. Some cool so quickly that they form an amorphous glass. Bowens reaction series predictable mineral associations. Igneous rocks and processes introduction igneous rocks comprise the bulk of the crust of the earth. Geologists sometimes classify igneous rocks based on how much silica they have. Igneous rocks pictures of intrusive and extrusive rock types. An igneous rock or a part of an igneous rock with a finegrained or aphanitic texture has crystals, but they are too small to recognized with the unaided eye. Describe the environments where basalt accumulates learning objectives lo 1. Igneous rock composition igneous rocks are commonly classified by their composition and texture. The bulk chemical composition of magma is dominated by the. Physical geology in our overview of the earth, we found out that earths internal heat combined with other mechanisms causes rocks to melt in the asthenosphere and lithosphere. Even experienced geologists presented with a simplelooking rock will examine it closely before identifying it.
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