Petrology and petrography of the igneous rocks of the. Students record data such as the color, the texture, if its intrusive or extrusive, if. Give a few examples of extrusive and intrusive igneous rocks. Theyre all connected to the endless rock cycle, moving from one type to a different and dynamic form, texture and even chemical composition of the method. Igneous and metamorphic petrology textures of igneous rocks lab 3 handout source. 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. What are engineering properties of igneous rock answers. Magma can cool to form an igneous rock either on the surface of the earth in which case it produces a volcanic or extrusive igneous rock, or beneath the surface of the earth, in which case it produces a plutonic or intrusive igneous rock. This can happen either above or below the earths surface, creating two different kinds of igneous rocks intrusive and extrusive. Igneous rocks that crystallize slowly beneath the earth s surface, typically have visible individual minerals. Igneous rocks and processes revised on 102011 page 5 of 10 finegrained or aphanitic.
Igneous rocks igneous rock forms when magma cools and hardens. Basalt, tuff, pumice are examples of extrusive igneous rock. Volcanic extrusive igneous rocks are usually fine grained, whereas plutonicintrusive igneous rocks are medium or coarse grained. If magma cooled inside the crust of the earth, the rocks will have larger minerals and referred to as plutonic or intrusive rocks. Intrusive rock is igneous rock, that is formed by the crystallized magma deep within the earth. An introduction to igneous rocks for the beginner a very simple igneous classification pdf version for printing alphabetical listing of igneous rocks links to picturesdescriptions bowens reaction series and igneous rock forming minerals pdf version magma types ultramafic, mafic, intermediate, felsic strategies of igneous rock classification. The rapid cooling of extrusive igneous rocks does not allow for the formation of crystallization, producing finegrained, vesicular and glassy rock. The rocks in the blue column are lighter in color and granitic. Describing igneous rocks worksheet students will learn how extrusive and intrusive igneous rocks form and get handson practice at telling extrusive and intrusive igneous rocks apart. Igneous rocks are formed when magma cools, either on earths surface or beneath it, though some may form by fragmentation of solidifying magma. As it does so, dissolved gases bubble out of the magma in much the same way as coke fizzes when you open the bottle. Those three different settings create three main types of igneous rocks.
Extrusive igneous rocks form as lava and ash become solid. Igneous rocks from the greek word for fire form when hot, molten rock crystallizes and solidifies. Glass no crystals forms in extrusive igneous rock subjected to extremely fast cooling. Igneous rocks pictures of intrusive and extrusive rock types.
Magma can cool to form an igneous rock either on the surface of the earth in which case it produces a volcanic or extrusive igneous rock. Igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material. Extrusive rock, any rock derived from magma molten silicate material that was poured out or ejected at earths surface. Extrusive igneous rocks tend to cool much more rapidly, and the minerals grow quicker and can not. A common example of an extrusive igneous rock is basalt. They are known as intrusive or plutonic igneous rocks. Igneous rocks form from cooled and solidified magma or lava. These rocks erupt onto the surface resulting in small crystals as the cooling takes place quickly. Typical occurrences of igneous rock bodies on the surface include lava flows, lava domes, necks and spines. Magmas and igneous rocks magma and igneous rocks igneous rocks are formed by crystallization from a liquid, or magma. Learn vocabulary, terms, and more with flashcards, games, and other study tools.
Intrusive igneous rocks form below the earths crust when magma cools and hardens before reaching the surface. When magma cools within the earth, the cooling proceeds slowly. So, intrusive igneous rocks would not let gases escapes, while extrusive igneous rocks will. They contain less than 45 percent silica, and are believed to originate from the mantle. Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the earth flows out extrudes onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. Two characteristics used to classify igneous rocks are and. The three minerals at the bottom do not form by reaction with the firstformed crystals. Therefore the rocks formed by this process are hard with large and coarsegrained crystals. Broadly igneous rocks are divided in two categories 1 extrusive rock 2 intrusive rocks.
Intrusive rocks form plutons and so are also called plutonic. The melt originates deep within the earth near active plate boundaries or hot spots, then rises toward the surface. Describe the process of igneous evolution and the role of 7. Most igneous rocks can be classified into three compositional groups, based on a particular assemblage of minerals. Plutonic bodies can be tabular, cylindrical or somewhere between equidimensional and irregular. Describe the environments where basalt accumulates learning objectives lo 1. Rocks that contain dark silicate minerals and plagioclase feldspar have an. Volcanic extrusive igneous rocks form by cooling and crystallization of lava or by consolidation of pyroclastic material. Extrusive igneous rocks form when magma reaches the earths surface a volcano and cools quickly. When volcanic material erupts and cools and crystallizes on earths surface, it forms a type of igneous rock called extrusive rock. Diagnostic properties of the common igneous rock forming minerals. Volcanic extrusive igneous rocks form by cooling and crystallization of lava or by consolidation of. Classifying igneous rocks mafic 4552% silica igneous rocks are dark colored because they are largely composed of caplagioclase and pyroxene. 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.
All igneous rocks derive either directly or indirectly from magma. Determination of intrusive and extrusive igneous rocks. Identify how igneous rock color relates to chemical 5. Formed from the cooling and consolidation of magma. Igneous rocks and processes revised on 102011 page 3 of 10 reaction series contains all of the common ironforming ferromagnesian minerals. When lava cools quickly at or near earths surface, we get extrusive volcanic igneous rocks with small or no crystals. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Glass no crystals forms in extrusive igneous rock subjected to extremely fast cooling this occurs when lava is ejected into the air or flows into water obsidian, pumice, volcanic ash, scoria obsidian. Rock formed of lava is called extrusive, rock from shallow magma is called intrusive, and rock from deep magma is called plutonic. Its the first thing you learn in a geology class very briefly the three types of rocks are igneous they form from the cooling of magma deep inside the earth.
There are 3 nice classes of rocks, igneous, sedimentary and metamorphic, and most of the time, they are easy to inform apart. Feb 18, 2015 introduction to the formation of igneous rocks, including, extrusive and intrusive rocks. Field description of igneous rocks pdf part of the successful field guide series, this book includes revised sections on granitic and basaltic rocks and for the first time a new chapter on the engineering. These rocks are finegrained since minerals crystallize too rapidly to form large crystals.
Lava flows are typically finer grained than intrusive igneous rocks. Some volcanic rocks like obsidian dont have any crystals at all. Chapter 4 magmas, igneous rocks, and intrusive activity. Igneous rocks reading, a supplement to the lab manual i introduction. By contrast, intrusive rocks are formed from magma that was forced into older rocks at depth within earths crust. The key difference between intrusive and extrusive igneous rocksthe size of crystals making them upis related to how rapidly melted rock cools. Igneous rock that was once underground can become exposed on earths surface. Igneous rocks form from the cooling of magma molten materials in the earths crust. Extrusive igneous rocks cool and solidify more quickly than intrusive igneous rocks.
Magma cools quickly less time for crystals to form. Igneous rocks that are composed primarily of quartz and feldspar have a granitic composition. Petrography the branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. Molten rock that flows out onto the surface is called lava.
This intrusive cooling process occurs very slowly in comparison to extrusive rock. A pluton is an igneous intrusive rock body that has cooled in the crust. Igneous rocks are rocks that solidify from molten rock. The rate of cooling of magma inside the earth is very slow. Igneous rocks form as molten rock cools and solidifies general characteristics of magma. The lower part of oceanic crust is comprised of gabbro. Large crystals form in intrusive igneous rocks, because they crystalize at depth and thus cool very slowly small crystals you can barely see without magnification, form in extrusive igneous rocks because the magma can cool rapidly. Identify the information revealed by igneous texture 4. The classification and nomenclature of igneous rocks are treated in the final section. When magma cools slowly inside earth, we get intrusive plutonic igneous rocks with large crystals. The igneous rocks of the stansbury mountains consist of several hypabyssal intrusions of intermediate and basic composition and four patches of extrusive s. The second edition of this unique pocket field guide has been thoroughly revised and updated to include advances in physical volcanology, emplacement of. Volcanoes erupt when magma reaches the earths surface.
Presentation slides include a graphic depiction of magma below earths surface, photographs of lava exploding and flowing, and closeups of. When molten rock is underground we call it magma whereas when it is above ground we call it lava, even though it is the same stuff. 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. Extrusive igneous whats your favorite rocks volcano. They are formed by the cooling of molten magma on the earths surface. Intrusive igneous rocks form inside the earth where they cool slowly, so they have large crystals. A less common group are the ultramafic rocks, which consist almost entirely of ferromagnesian minerals and have no feldspars or quartz.
Extrusive igneous rocks cool and harden quickly since they form on the earths surface, so they do not have the time to form crystals. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate. Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies. Hand out rock box to each pair and a magnifying glass to each student. Which magma is most likely to quench congeal to a natural glass. Plutonic rocks are always intruded into preexisting sedimentary. Pictures and brief descriptions of some common igneous rock types are shown on this page. Basalt is the most common extrusive volcanic igneous rock.
These rocks are called volcanic or extrusive rocks. The rocks resulting from volcanic eruptions cool rapidly and are known as extrusive igneous rocks, because the magma was extruded from the earth. Examples of finegrained extrusive rock include rhyolite, andesite and basalt. Characteristics of magma types of magma types of magma are determined by chemical composition of the. Depending on where the magma cools determines the relative size of the crystals in the igneous rock. Volcanic rocks are also called extrusive igneous rocks, as opposed to intrusive igneous rocks. The sizes, shapes, and arrangements of mineral grains in an igneous rock are known as. Write the names of three igneous rocks in the provided spaces.
Describes the features of intrusive and extrusive igneous rocks that cool slowly and rapidly, respectively. In contrast, intrusive rock refers to rocks formed by magma which cools below the surface. Intermediate rocks, such as andesite, fall between the mafic and felsic classifications. Some igneous rocks consist of mineral grains that are too small to be seen with the naked eye.
This file is licensed under the creative commons attributionshare alike 4. Two sills, one sole injection, and two plugs represent an andesitic to trachyandesitic phase of intrusion and three or four diabase dikes appear to be volcanic fissures. Fossils n the rock 1 these are formed from layers rock fragments or dead matter laid down in lakes or seas over millions of years. Examples include basalt, rhyolite, andesite, and obsidian. The violence of an erupon is related to how easily gases can. Understanding igneous rocks and the minerals of which they are comprised are fundamental knowledge taught within the k12. Plagioclase makes up the continuous reaction series. Extrusive rocks there are two types of igneous rocks. This 3page worksheet is to be used for notes and a handson activity.
Extrusive igneous rocks volcanoes and volcanic rocks igneous rock names and compositions intrusive rock name peridotite gabbro diorite granite composition name ultramafic mafic intermediate silicic felsic volcanic rock name komatiite basalt andesite rhyolite. Intrusive rocks, in general, have density 150200pcf their compressive strength ranges form 330 psi100. In practice, this means that the average dimension of the crystals is less than 1 millimeter. The deeper the magma, the slower it cools, and it forms larger mineral crystals. Examples of intrusive igneous rock include granite, diorite, gabbro and peridotite. Dynamic music pumps up viewers as they learn about intrusive and extrusive igneous rocks. Some cool so quickly that they form an amorphous glass. Plutonic intrusive igneous rocks form as magma cools and crystallizes within earth. Igneous rocks are called intrusive when they cool and solidify beneath the surface.1288 248 640 1384 317 559 50 1082 1347 477 859 1047 411 1134 931 693 1009 1391 196 397 1412 1465 1256 1318 9 289 780 1660 557 1066 1575 89 1040 1441 767 994 334 380