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Igneous rocks  armetta
 

Igneous rocks armetta

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    Igneous rocks  armetta Igneous rocks armetta Document Transcript

    • ROCKS: You probably don’t realize it, but we depend on many rocks in our everyday lives. Rocks have different chemical and physical properties that make them quite useful to us. Besides providing a nice hard place for us to stand on Earth, we userocks for the construction of our homes, for fuel,and for the creation of statues and art. Go home today and look around your house. You may be surprised by what rocks you find.
    • ROCKS:A ROCK is composed of one or moreminerals. Rocks composed of only one mineral are said to be MONOMINERALLIC. This is a photo of a slice of Dunite, a monominerallic igneous rock, under a microscope. Almost all of the grains in this rock are olivine. Note the high order interference colors of olivine and the minor secondary calcite which occurs as veinlets through the sample.
    • ROCKS:Most rocks arePOLYMINERALLIC,that is, made ofmany differentminerals. There areover 2,500 differentminerals. However,there are 10-15 minerals known as the rock- forming minerals, which compose about 90% of all the rocks in Earth’s crust.
    • METHOD OF FORMATION: Rocks are classified by their METHOD OF FORMATION, into three groups:1) IGNEOUS2) SEDIMENTARY3) METAMORPHIC Let’s take a more detailed at each.
    • IGNEOUS ROCKS:Igneous rocks form from the MELTING and SOLIDIFICATION (hardening) of molten material from within the Earth.
    • IGNEOUS ROCKS:Molten material within the Earth is called MAGMA. When this molten material reaches Earth’s surface it’s called LAVA. LAVA: ON OR NEAR EARTH’S SURFACE MAGMA: INSIDE OF EARTH
    • IGNEOUS ROCKS:Igneous rocks are solid, hard, and compact and are composed of randomly arranged INTERGROWNMINERALCRYSTALS. GRANITE IS AN IGNEOUS MAYBE YOU CAN SEE ROCK WITH COARSE THEM BETTER CLOSE UP? GRAINED CRYSTALS.
    • TEXTURE:Igneous rocks are best identified by their texture, environment of formation, and mineral composition Texture describes a rock’s “grain appearance” which is determined by the size of the crystal and the arrangement of the crystals. There are FOUR textures: glassy, fine, coarse, and very coarse.
    • TEXTURE:1) GLASSY: A glassy texture forms when a mineral cools so quickly that no crystals are visible. Glassy textures occur when there is a rapid drop in temperature and pressure. This condition OBSIDIAN exists when magma reaches Earth’s surface through a volcano.
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • TEXTURE: There are TWO types of glassy texture: PUMICEa) VESICULAR: A vesicular texture exhibits gas pockets and the rock appears holey. Ex: Pumiceb) NON-VESICULAR: OBSIDIAN A non-vesicular texture looks like glass. Ex: Obsidian
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • TEXTURE:2) FINE: A fine texture RHYOLITE forms when a mineral cools quickly at or near Earth’s surface. The grain size is less than 1mm. Ex: Rhyolite BASALT SCORIA ANDESITE
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • TEXTURE:3) COARSE: A fine texture GRANITE forms when a mineral cools SLOWLY WITHIN the Earth under high pressure. The grain size ranges from 1-10 mm. Ex: Granite PERIDOITE DIORITE GABBRO
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • TEXTURE:4) VERY COARSE: A course PEGMATITE texture forms when a mineral cools very slowly within the Earth, producing grain sizes 10 mm or larger. Ex: Pegmatite A CLOSER LOOK!!!
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • TEXTURE: TEXTURE IS DETERMINED BY THE LENGTH OF COOLING! Rocks that cool FAST have SMALLER crystals. Rocks that cool SLOW have LARGER crystals. SMALL LARGECRYSTALS CRYSTALSCOOLED COOLED FAST SLOWLY
    • RATE & DEPTH OF COOLING: SUPER IMPORTANT FACT! The grain size of igneous rocks depends on the RATE and DEPTH at which magma cools. ROCK NAME GRAIN SIZE A ENVIRONMENT The diagram Basalt 0.1 mm Surface B shows the relationship Diabase 1 mm Nearbetween grain size C Surfaceand rate/depth of cooling. Granite 10 mm Deep Slow Moderate Fast COOLING RATE
    • RATE & DEPTH OF COOLING:CRYSTAL SIZE CRYSTAL SIZE CRYSTAL SIZE COOLING RATE COOLINGTIME DEPTH THESE ARE GRAPHING RELATIONSHIPS THAT YOU SHOULD KNOW.
    • RATE & DEPTH OF COOLING:CRYSTAL SIZE CRYSTAL SIZE CRYSTAL SIZE COOLING RATE COOLINGTIME DEPTH THESE ARE GRAPHING RELATIONSHIPS THAT YOU SHOULD KNOW.
    • ENVIRONMENT OF FORMATION:By studying a rock’s texture, you can infer a rock’s environment of formation. There are TWO different environments of formation.1) EXTRUSIVEorVOLCANIC: This is when an igneous rock hardens NEAR the Earth’s surface or ON the Earth’s surface to form a rock with small or no crystals. These rocks are found by volcanoes.
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • ENVIRONMENT OF FORMATION:2) INTRUSIVEorPLUTONIC: This is when an igneous rock hardens within the Earth to form large crystals. When magma doesn’t erupt it can flow underground. Underground magma flows are called INTRUSIONS because they can move into and through fractures (cracks) in rock. If an intrusion hardens, it produces a large mass of igneous rock called a PLUTON.
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • CHEMICAL COMPOSITION: A rock’s chemical composition refers to a rock’s mineral make-up. Igneous rocks are generally described as having either a FELSIC composition or a MAFIC composition.1) FELSIC COMPOSITION: Rocks with a felsic composition tend to contain a high percentage of the minerals potassium feldspar and quartz. They are RICH IN ALUMINUM (Al) and low in both iron (Fe) and magnesium (Mg). These rocks are usually LIGHTER IN COLOR and LOWER IN DENSITY than mafic rocks. Felsic rocks make up a large portion of continental crust. The granite family of rocks is felsic.
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT: NOTE:Even thoughOBSIDIAN is dark in color, it is consideredFELSIC, be cause it is low in density.This is the one exceptionto the rule!
    • CHEMICAL COMPOSITION:2) MAFIC COMPOSITION: Rocks with a mafic composition tend to contain a high percentage of the minerals plagioclase feldspar and pyroxene. They are RICH IN IRON (Fe) and MAGNESIUM (Mg) and low in ALUMINUM (Al). These rocks are usually DARKER IN COLOR and HIGHER IN DENSITY than felsic rocks. Mafic rocks are most common in the ocean basins. The Gabbro family of rocks is mafic.
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • MINERAL COMPOSITION: WHAT IS MINERAL COMPOSITION? Mineral composition refers to the different minerals that a rock is made up of and the percentages of these minerals.Granite is mostly made up of POTASSIUM FELDSPAR(pink/gray), BIOTITE MICA (black), and QUARTZ (clear/white).
    • MINERAL COMPOSITION:
    • SCHEME FOR IGNEOUS ROCK IDENTIFICATION IN YOUR ESRT:
    • FINDING THE MINERAL COMPOSITION USING YOUR ESRT: You can determine the possible mineral composition of specificigneous rocks by looking at your ESRT. Simplyfind a rock name on thechart, then look at the minerals found in the column under that rock name. Your rock name can contain varying amounts of those materials.
    • FINDING THE PERCENTAGE OF MINERALS IN A IGNEOUS ROCK USING YOUR ESRT: You can determine the possible mineral composition of specificigneous rocks by looking at your ESRT. Simplyfind a rock name on thechart, then look at the minerals found in the column under that rock name. Your rock name can contain varying amounts of those materials.
    • FINDING THE PERCENTAGE OF MINERALS IN A IGNEOUS ROCK USING YOUR ESRT: You can determine the possible mineral composition of specificigneous rocks by looking at your ESRT. Simplyfind a rock name on thechart, then look at the minerals found in the column under that rock name. Your rock name can contain varying amounts of those materials.
    • REVIEW OF IGNEOUS ROCKS: INTRUSIVE EXTRUSIVE ( PLUTONIC) (VOLCANIC) INSIDE EARTH ENVIRONMENT ON/NEAR EARTH’S OF FORMATION SURFACE SLOW SPEED OF FAST COOLING LARGE SIZE OF SMALL CRYSTALCOARSE, VERY COARSE NAME OF FINE, GLASSY TEXTUREGRANITE, DIORITE, GABB ROCK EXAMPLES OBSIDIAN, SCORIA, PURO, PERIDOITE, DUNITE, MICE, RHYOLITE, AND PEGMATITE ESITE, BASALT
    • REVIEW OF IGNEOUS ROCKS: FELSIC MAFIC Aluminum (Al) MINERAL Iron (Fe) Silicon (Si) COMPOSITION Magnesium (Mg) Light COLOR Dark Low DENSITY High TEMPERATURE AT Low WHICH MINERALS High IN ROCK CRYSTALLIZEGranite, Pegmatite, Rhyolite ROCK EXAMPLES Scoria, Basalt, Gabbro, , Pumice, Obsidian Peridoite, Dunite