What % of the rocks in the world are igneous and what % is Metamorphic?
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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.
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A rock is a naturally occurring aggregate of minerals and/or mineraloids. Rocks are classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. These indicators separate rocks into igneous, sedimentary and metamorphic. They may also be classified according to grain size, in the case of conglomerates and breccias or in the case of individual stones.\n\nMinerals are natural compounds formed through geological processes. The term "mineral" encompasses not only the material's chemical composition, but also the mineral's structure. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms (organic compounds are excluded). The study of minerals is called mineralogy.
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Igneous, they tell us a lot about what the age of the Earth and location of the poles.\n\nSedimentary, tell us the climate of an area and preserve fossils.\n\nMetamorphic, they look cool but are hard to tell anything from.  Their general location tells us of orogenies and faults.\n\nAll rocks are important and different geologists study different things.  Oil bearing shale is important to some geologist since if we can figure out an economical method of extraction we wouldn't be dependent on other countries for oil.\n\nGeology is like a big puzzle, and it's interesting seeing how the pieces fit together.
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Magma is the molten rock when it is under the surface.  It becomes lava when it reaches the surface.\n\nThe tremendous pressures in the Earth's mantle heat rock and liquify it.
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Mostly quartz and orthoclase feldspar. Any number of other minerals can make up the rest.
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Porphyry & Basalt are both igneous.\n\nPorphyry is an intrusive igneous rock w/ different crystal sizes.\n\nPorphrytic is a texture term that is often used to describe certain types of igneous rocks having two distinct crystal sizes. The large crystals inside the rock are called phenocrysts. Porphyrtic granite is an example. I tell students that it reminds me of a chocolate chip cookie w/ the large crystals representing the chocolate chips. That usually helps them to get it.\n\nBasalt is an extrusive igneous rock composed mainly of darker minerals such as magnesium.\n\nLimestone is a sedimentary rock as is shale.
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Feldspar is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earth's crust. Feldspars crystallize from magma in both intrusive and extrusive rocks; they occur as compact minerals, as veins, and are also present in many types of metamorphic rock. Rock formed entirely of plagioclase feldspar (see below) is known as anorthosite. Feldspars are also found in many types of sedimentary rock.\n\nThis group of minerals consists of framework or tectosilicates:\n\n- orthoclase a potassium-aluminium silicate,\n- microcline also a potassium-aluminium silicate, and\n- plagioclase a sodium-aluminium silicate to a calcium-aluminium silicate isomorphous series:\n          o albite\n          o oligoclase\n          o andesine\n          o labradorite\n          o bytownite\n          o anorthite.
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Well, sedimentary has "sediment" in it. You know, the yucky mud stuff on the bottom of a river or stream. That's what sedimentary rocks are made of.\n\nIgneous looks like ignite, which is to start a fire. Volcanoes have red-hot magma in them, and that's what igneous rocks are formed from.\n\nA metamorphosis is a change from being one thing to being something else (like a caterpillar becoming a butterfly.) Metamorphic rocks are formed when other rocks are transformed by heat and pressure deep withing the earth's crust. \n\nI know you probably wanted some kind of clever mnemonic device, but in this case all you have to do is remember the meanings of three common words.
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3 basic types of rocks\n\nIgneous Rocks-Igneous rocks are crystalline solids which form directly from the cooling of magma. This is an exothermic process (it loses heat) and involves a phase change from the liquid to the solid state. The earth is made of igneous rock - at least at the surface where our planet is exposed to the coldness of space. Igneous rocks are given names based upon two things: composition (what they are made of) and texture (how big the crystals are).\n\nSedimentary Rocks-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. Sedimentary rocks are called secondary, because they are often the result of the accumulation of small pieces broken off of pre-existing rocks. There are three main types of sedimentary rocks:\n\nMetamorphic Rocks-The metamorphics get their name from "meta" (change) and "morph" (form). Any rock can become a metamorphic rock. All that is required is for the rock to be moved into an environment in which the minerals which make up the rock become unstable and out of equilibrium with the new environmental conditions. In most cases, this involves burial which leads to a rise in temperature and pressure. The metamorphic changes in the minerals always move in a direction designed to restore equilibrium. Common metamorphic rocks include slate, schist, gneiss, and marble.
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pre-cambrian: 88%\n\npaleozoic: 7%\n\nMesozoic: 4%\n\nCenozoic: 1%
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* Igneous Rocks\nIgneous 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. As these pockets of magma cool slowly underground, the magma becomes igneous rocks. \n\nIgneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground.\n\n* Metamorphic Rocks\nMetamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks. How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change. If you exam metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.\n\n* Sedimentary Rocks\nFor thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away\nby wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.
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Here is a chart of various estimates of the mantle's composition that have been made:\nhttp://www.mpch-mainz.mpg.de/~jesnow/Ozeanboden/2004/Lecture4/Composition.html\n\nThe answer in terms of minerals is (I quote) "The uppermost mantle is comprised of a peridotite with about 60% olivine 30% enstatite 6% clinopyroxene, 2% plagioclase and 2% spinel. At slightly greater depth, the plagioclase disappears and is replaced by spinel and clinopyroxene. Deeper still, garnet appears." from the above site. \n\nThe other thing you should realize is that while the earth's mantle may be 'plastic' it is not molten. From Wikipedia: "Although these temperatures far exceed the melting points of the mantle rocks at the surface, particularly in deeper ranges, they are almost exclusively solid. The enormous lithostatic pressure exerted on the mantle prevents them from melting."  From: http://en.wikipedia.org/wiki/Mantle_%28geology%29\n\nMagma coming from volcanoes actually originates in the asthenosphere, which is above the mantle.
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Metamorphic rocks are already existing rocks that change under heat, pressure or in chemical reactions (usually underground). Examples are Gneiss (that froms from Granite), Slate (formed from Shale), and Quartzite (formed from Sandstone).\n\nSedimentary rocks are rocks made from sediment (haha makes sense, no?) which can be both organic (fossils!) or inorganic. They are formed into a solid rock through a variety of different forces, including erosion, deposition, compaction, and cementation. There are 3 major groups of sedimentary rocks, which are clastic (formed from the compression of rock fragments), organic rocks (Key word: ORGANIC, aka the remains of plants and animals), and chemical rocks (formed when a solution dissolves, & minerals are left behind). Examples:\nClastic: Shale, Sandstone, Conglomerate, and Breecia\nOrganic: Coal, Limestone\nChemical: Halite, Gypsum\n\nIgneous rocks are formed from magma or lava. They are classifed according to where they were formed-- extrusive rocks are formed from lava on Earth's surface, while intrusive rocks are formed from hardened magma beneath Earth's surface. Texture and mineral composition are also factors of classification. Examples include granite (which is extremely abundant), Rhyolite, Pegmatite, Porphyry, Basalt, Pumice, and Obsidian.
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Orogeny is the building of mountains.  Most mountains are formed when one techtonic plate subducts under another pushing the top plate up.  Mount Everests includes sedimentary rock that was part of the sea.  The subduction can sweep seawater and silt under a plate setting up the conditions for huge volcanoes as magma is formed and rises through the stratta above as in the Andes.
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Minerals are what make up rocks.  When Earth's rocks erode, these minerals are released.  A lot of times, erosion takes place in higher elevation areas because the denudation (erosion) rate of higher elevations is also higher than lower elevations and streams usually stem from places of higher elevation.  Minerals then are deposited into these streams.
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The other answerer has a point. However, a little thought will get you the answer. \n\nD. Sialic or Mafic? These terms describe composition. What could that have to do with grain size?\nC. % Ferromagnesian minerals? Again, composition has nothing to do with grain size. \nD. % Quartz? Same reason again. \nA. magma or lava? Okay, do you know the definitions of these? Magma is BENEATH the earth surface, lava is erupted onto the surface. Which one cools faster? It will have the SMALLEST crystals. The slow cooling rock will have time for LARGE crystals to grow.
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Igneous rocks are formed with heat. They are most commonly found around volcanoes. Metamorphic rocks are formed with heat and pressure. Sedimentary rocks, like sandstone and limestone, are formed by pressure.