#ROCKS #IGNEOUS #question-what do you think is the most valuable type of igneous rock? Why did you say so? WHAT DO WE KNOW ABOUT THE IGNEOUS ROCK? -Igneous rocks are formed from the solidification of molten rock material. According to the discovery, There are two basic types of IGNEOUS ROCK: 1) intrusive igneous(PLUTONIC:crystallizes at the dept in the earth) rocks such as diorite, gabbro, granite and pegmatite that solidify below Earths surface. 2) extrusive igneous(VOLCANIC:cools & crystallizes on the surface of the earth) rocks such as andesite, basalt, obsidian, pumice, rhyolite and scoria that solidify on or above Earths surface. Pictures and brief descriptions of some common igneous rock types are shown on this page. ABOUT THE IGNEOUS: The main thing about igneous rocks is that they were once hot enough to melt. The following traits are all related to that. -Because their mineral grains grew together tightly as the melt cooled, they are relatively strong rocks. -Theyre made of primary minerals that are mostly black, white or gray. Any other colors they may have are pale. -Their textures generally look like something that was baked in an oven. The even texture of coarse-grained granite is familiar from building stones or kitchen counters. Fine-grained lava may look like black bread (including gas bubbles) or dark peanut brittle (including larger crystals). ORIGIN:WHY IGNEOUS ROCK? The word igneous comes from the Latin for fire, and what igneous rocks have in common is that they formed by the cooling and crystallization of a melt. THERE ARE SOME TYPES OF IGNEOUS ROCKS: Igneous rocks are classified by the minerals they contain. The main minerals in igneous rocks are hard, primary ones: feldspar, quartz, amphiboles and pyroxenes (together called dark minerals by geologists), and olivine along with the softer mineral mica. WHERE IGNEOUS ROCKS ARE FOUND The deep sea floor (the oceanic crust) is made almost entirely of basaltic rocks, with peridotite underneath in the mantle. Basalts are also erupted above the Earths great subduction zones, either in volcanic island arcs or along the edges of continents. Prepared by:K.B.O.D SOURCES: -geology.about -earth science(13th edition,TARBUCK)
Posted on: Sat, 02 Aug 2014 13:28:03 +0000
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