When most people think about igneous rocks they envision a volcano erupting pumice and lava. Texturs and structures of igneous rocks are controlled by the physic8. Theres just a bewildering number of rocks to remember, minerals to be familiar with and textures to recognise. A more indepth investigation of rock types occurs when students observe the rocks around the schoolyard during a rock walk. Basalt extrusive rock and granite intrusive rock are two of the most common igneous rock types on the earth, and cover most of the igneous deposits on the planet. Petrogenesisthe interpretive part of the science in which we try to constrain the origin of igneous rocks, i. Each of these is introduced simplistically below, and then further explored in other pages of the site. In this structure, the volcanic igneous body appears as a pile of numerous overlapping pillows or sacks.
Rock cycle notes three types of rocks sedimentary igneous metamorphic sedimentary rocks sediment is produced through the process of weathering. An igneous rock is any crystalline or glassy rock that forms from cooling of a magma 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. Usually, the rocks in deep ocean floors are known to be basaltic in nature, while the rocks in the continental mass are granitic in nature. In volcanic environments they generally result from explosive activity or the incorporation of solid fragments by moving lava. Rocks that are formed on the surface of the earth by solidification lithification of weathered or dissolved material are sedimentary. The book encourages a deeper comprehension of the subject by explaining the. Find materials for this course in the pages linked along the left. Mineral resources of igneous and metamorphic origin. 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 structures the structures of igneous rocks are large scale features, which are dependent on several factors like. Describe the process of igneous evolution and the role of 7.
When the molten rock magma cools and solidifies before it reaches the surface it forms intrusive igneous rock. 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. Extrusive igneous rocks erupt onto the surface, wherever they cool quickly to make little crystals. Introduction structural geology is study of the three dimensional of the rock units with respect to their deformational histories. Owing to their interlocked crystals, igneous rocks boast of a strong and stable structure. Igneous rocks result from the final solidification of magma at the surface or at variable depths within the earth, as well as from the eventual consolidation of fragmented debris. Intrusive rocks are also called plutonic rocks, named after the greek god pluto, god of the underworld. Ternary classification of felsic to mafic igneous rocks. Phaneritic, vesicular, aphanitic, porphyritic, poikilitic, glassy, pyroclastic, equigranular, and spinifex. Primary structures of sedimentary and igneous rocks. Igneous rocks form from the cooling of magma molten materials in the earths crust. Poikilitic and ophitic structures remain unaffected, and the min erals are fresh.
Mount rushmore, where the presidents faces are carved in the mountainside, was chiseled out of granite, another igneous rock. Calculated viscosities of anhydrous silicate liquids at one atmosphere pressure, calculated by the method of bottinga and weill 1972 by hess 1989, origin of igneous rocks. Magmas and igneous rocks magma and igneous rocks igneous rocks are formed by crystallization from a liquid, or magma. Ii occurrence, texture, and classification of igneous rocks gezahegn yirgu encyclopedia of life support systems eolss summary in this article, the manner in which igneous rocks occur in nature is introduced, followed by a discussion of the general textural features and appearance of these rocks. Primary structures of sedimentary and igneous rocks 1. Atlas of igneous rocks and their textures a companion volume to the atlas of rockforming minerals in thin section, this fullcolour handbook is designed to be used as a laboratory manual both by elementary students of earth sciences undertaking a study of igneous rocks in thin section under the microscope, and by more advanced students and teachers as a reference work. Igneous rocks formed of cooled lava or volcanic ejecta are common, but most molten material cools below earths surface. Igneous rocks are classified through the simultaneous consideration of two factors. Igneous rock is formed by magma or lava cooling and solidifying. Principles of igneous and metamorphic petrology second edition this textbook provides a basic understanding of the formative processes of igneous and metamorphic rocks through quantitative applications of simple physical and chemical principles. Igneous structures and field relationships figure 4. Textures and structures of igneous rocks igneous rock. Which observation about the rock best supports this classification.
Principles of igneous and metamorphic petrology second. Igneous textures are used by geologists in determining the mode of origin igneous rocks and are used in rock classification. Extrusive igneous rocks tend to cool much more rapidly, and the minerals grow quicker and can not get as large. 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. 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. A good example of intrusive igneous rock is granite. Igneous rocks, sedimentary rocks and metamorphic rocks. These rocks embody andesite, basalt, obsidian, pumice, rhyolite, scoria, and tuff. 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. Igneous rocks are formed by the solidification and cooling of magma in volcanic. Arc 3 delves into how rocks and landforms change over time. They are usually brown to gray in color and may have fossils and water or wind marks. Rock composed entirely of crystals which may or may not be visible without magnification. Read igneous rocks to find the answers to these questions and many more.
If grains are not apparent, can fall back on the observation that mafic minerals tend to be dark or green, whereas felsic minerals tend to be light grey or pink. Identify the information revealed by igneous texture 4. In the modern oceans, the mafic association is found in two specific settings. Some cool so quickly that they form an amorphous glass.
Igneous rocks are produced this way but most igneous rocks are produced deep underground by the cooling and hardening of magma. 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. Under high temperature and pressure, the sediment becomes compacted. Igneous rocks that crystallize slowly beneath the earth s surface, typically have visible individual minerals. Indicates cooling so rapid that no crystal growth could occur, i. Examples of intrusive igneous rocks are diorite, gabbro, granite, pegmatite, and peridotite. This structure refers to linear and nearly parallel features occurring in volcanic rocks which develop as a consequences of the flow of the lava.
Each kind of texture has a variety of different characteristics that make them unique. Textures and structures of igneous rocks free download as powerpoint presentation. Occurrence, texture, and classification of igneous rocks. Igneous rocks and processes introduction igneous rocks comprise the bulk of the crust of the earth. Larger scale features, such as fractures and layering, are considered rock structures in comparison. In this sense, igneous rocks are formed when molten rock magma solidifies either underneath the earth crust to form plutonic intrusive igneous rocks or on the surface of the earth to form volcanic extrusive igneous rocks. Igneous rocks formed of cooled lava or volcanic ejecta are common, but most molten material cools below.
Apr 21, 2017 primary structures of sedimentary and igneous rocks 1. Mineral resources of igneous and metamorphic origin learning outcomes 1. Igneous and sedimentary rocks deep below the earths surface are buried under the huge weight of the rocks, sediments and soil above them. The felsic minerals include quartz, tridymite, cristobalite, feldspars plagioclase and alkali feldspar, feldspathoids nepheline and leucite, muscovite, and. Glg 333 igneous textures and structures the following is a reorganization and amplification of blatt and tracy, 1996, pages 3944. Important facts about the popular igneous rock science. This cheat sheet pack contains some practical advice on how to do. Lecture 5 plutonic structures and field relationships friday, february 4th, 2005. Sedimentary rocks such as limestone or shale are hardened sediment with sandy or claylike layers strata. The texture of igneous rocks igneous rock, rock science. These rocks include andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff. This reader emphasizes how all igneous rocks are formed and explores how the formation is related to igneous rock classification. The sio 2 may occur as free quartz or be combined with varying proportions of elements to form minerals such as feldspar. There are nine main types of igneous rock textures.
In practice, this means that the average dimension of the crystals is less than 1 millimeter. Internal structures of igneous rocks the rocks shows little trace of any crushing or recrystallization. Teacher notes if your students have completed the plate tectonic units on volcanoes, they should be familiar with different volcanic environments. Igneous rocks such as granite or lava are tough, frozen melts with little texture or layering. 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. In either the mantle or crust of a planet, the magma can be derived from partial melts of existing rocks. Extrusive igneous rocks finegrained or glassy lava flows volcanoes intrusive igneous rocks medium to coarsegrained hypabyssal transitional between fine and coarsegrained.
Igneous rock evolution plate tectonics and igneous rock distribution. Igneous rocks and processes revised on 102011 page 5 of 10 finegrained or aphanitic. Find interesting information and a range of examples that help explain what igneous rocks are and what makes them different from other kinds of rocks. Types of tabular igneous bodies in bedded strata based on method of emplacement. Lecture notes 3 igneous rocks glendale community college. This type of structure is produced under stress and in.
Forms and structures of igneous rocks springerlink. More information aphanitic a not, phaner visible rocks in contrast to phaneritic rocks, typically form from lava which crystallize rapidly on or. Describe the processes that act to form igneous rock. In the last lecture we looked at the nature and classification of igneous rocks. You will also definitely want to look at mackenzie et al. Rock identification adapted from don peck page 5 of 16 the rock identification key about the rock identification key this rock key has been designed and written to assist children and adults in identifying the common rocks they find in their back yards and on memorable vacations. Igneous rock is formed when magma cools and solidifies, it. We established that igneous rocks do vary in both texture and composition, and that the two properties can be used to classify them. It occurs particularly in soda rich basaltic rocks known as spillites.
To simplify the discussion we are severely reducing the number of igneous rocks you need to know to an essential few. The term igneous comes to us from the latin word ignis which means fire. Feb 18, 2015 introduction to the formation of igneous rocks, including, extrusive and intrusive rocks. Hydrothermal activity spatially associated with ultramafic rocks, usually serpentinites, has been observed at several localities proximal. Rocks formed from magma at depth are intrusive, or plutonic rocks. An introduction to igneous rocks requires exploration of three core ideas. The rocks resulting from volcanic eruptions cool rapidly and are known as extrusive igneous rocks, because the magma was extruded from the earth. Metamorphic rocks can likewise form sedimentary rocks. Metamorphic structures definite mechanical conditions and recrystallization determine the metamorphic structures. 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. The top diagram is for extrusive rocks and the lower is for intrusive rocks. 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. Introduction to igneous rocks an igneous rock is any crystalline or glassy rock that forms from cooling of a magma. While some igneous rocks are formed as a result of the solidification of melts produced by highgrade metamorphism, most are formed as a result of the partial melting of the mantle.
Recognizing igneous composition need to be able to identify the common minerals in igneous rocks. The igneous rocks are those which have solidified from a molten condition. Thus, rapid cooling at the earths surface of extrusive molten material, or lava, results in the growth. These are various features that express the accumulation of fragments or the rupturing and dislocation of solid material. Igneous rock igneous rock mineralogical components. South orangetown central school district educational. Intrusive igneous rocks cool slowly and form very large crystals. Jan 15, 20 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. Gradational border zones between homogeneous igneous rock light and country rock dark.
Degassingvolatiles release hydrothermal alteration and lowgrade metamorphism crystal accumulation presence of xenocrysts and. Explain how different mineral resources both igneous and metamorphic form at plate boundaries. Model to assess the quality of magmatic rocks for reliable. Igneous rock or magmatic rock, is one of the three main rock types, the others being. 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.
Some very common metamorphic textures and structures are discussed briefly as follows. Identify how igneous rock color relates to chemical 5. Igneous petrology cheat sheet 1 imperial college london. Bostonitic radial texture found in certain medium and finegrained dike rocks. The table below shows classification of major groups of igneous rocks based on their mineral composition and texture. Students then simulate the rock cycle using a dice game in the classroom and try to determine which type of rock their pet rock is. Igneous rock textures principlethe fundamental principle behind igneous rock textures is that grain size is controlled by cooling rate. Intrusive rocks become exposed on the earths surface when overlying material is eroded away. Igneous rocks that cooled on the surface are termed extrusive. Igneous rocks pictures of intrusive and extrusive rock types. Describe the processes that act to form metamorphic rock. Describe the environments where basalt accumulates learning objectives lo 1.
Experimental studies indicate that crystals with simple structures tend to nucleate more easily than those with more complex structures e. Five major types of metamorphic structures have been recognised as follows. Rocks formed from lava are extrusive, or volcanic rocks. Rocks like these contain mostly black, white andor gray minerals. Igneous rocks form as molten rock cools and solidifies general characteristics of magma. Igneous petrology cheat sheet 1 practical igneous petrology for dummies we can all be dummies when it comes to looking at igneous rocks. Igneous rock identification university of washington. Pdf types and physical properties of igneous rocks of popov. Igneous rocks thus occur in two ways, either as extrusive on the surface rocks or as intrusive below the surface bodies. The molten rock, or lava, has cooled to form igneous rocks. This is a singularly unilluminating definition, because it doesnt conjure up in the mind of the uninitiated any of the great variety of interesting and significant geometries that get produced by the physical. The associated earlier flows and sediments show no such structure as would have developed if the gabbro had been metamorphosed.
The classification for igneous, sedimentary, metamorphic, and pyroclastic rocks is shown on figures 41, 42, 4. You may also want to refer to barker, 1983, pages 106120. 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. Igneous rocks constitute one of the three principal classes of rocks, the others being metamorphic and sedimentary. Metamorphic textures and structures geology universe. Igneous rocks form when magma molten rock cools and crystallizes, either at volcanoes on the surface of the earth or while the melted rock is. Large rocks are broken down very gradually and the smaller pieces are transported by wind, water, and ice. Coastal igneous rocks oceanic igneous rocks igneous rock classification origins and differentiation of magma origins of magma magmatic differentiation continental igneous rocks a wide variety of igneous rocks occur in the continental lithosphere, a reflection of its heterogeneous nature compared to oceanic lithosphere. Formation, classification, and identification of igneous rocks next. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals.
1510 71 888 638 685 914 952 563 1410 1500 836 876 519 493 663 1566 1201 1304 658 1094 106 321 373 1160 1055 407 899 939 377 1303 697