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Showing posts from May, 2022

Quartz

  Quartz   Quartz is hexagonal and commonly occurs as crystals ranging in size form microscopic to crystals weighing several tons. Where it crystallizes unhindered by other crystals, such as in cavities in rock or in a liquid containing few other crystals, it shows well-developed hexagonal prisms and sometimes showing apparent hexagonal pyramids or dipyramid. When it crystallizes in an environment where growth is inhibited by the surroundings, it rarely show crystal faces. It is also found as microcrystalline masses, such as in the rock chert, and as  fibrous masses, such as in chalcedony. Vitreous lusture.   As visible crystals, Quartz is one of the more common rock forming minerals. It occurs in siliceous igneous rocks such as volcanic rhyolite and plutonic granitic rocks. It is common in metamorphic rocks at all grades of metamorphism, and is the chief constituent of sand. Because it is highly resistant to chemical weathering, it is found in a wide variety of sedimentary r
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Quartz

  Quartz   Quartz is hexagonal and commonly occurs as crystals ranging in size form microscopic to crystals weighing several tons. Where it crystallizes unhindered by other crystals, such as in cavities in rock or in a liquid containing few other crystals, it shows well-developed hexagonal prisms and sometimes showing apparent hexagonal pyramids or dipyramid. When it crystallizes in an environment where growth is inhibited by the surroundings, it rarely show crystal faces. It is also found as microcrystalline masses, such as in the rock chert, and as  fibrous masses, such as in chalcedony. Vitreous lusture.   As visible crystals, Quartz is one of the more common rock forming minerals. It occurs in siliceous igneous rocks such as volcanic rhyolite and plutonic granitic rocks. It is common in metamorphic rocks at all grades of metamorphism, and is the chief constituent of sand. Because it is highly resistant to chemical weathering, it is found in a wide variety of sedimentary r
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Meteorites

Meteorites - chunks of rock from space that land on Earth. Meteors are not meteorites Like meteorites, meteors are objects that enter Earth's atmosphere from space. But meteors-which are typically pieces of comet dust no larger than a grain of rice-burn up before reaching the ground. Common minerals in meteorites : ·        kamacite, ·        taenite (both Ni-Fe alloys, different crytall structures) ·        pyroxene (especially bronzite) ·        olivine ·        plagioclase   Kinds of meteorites : v irons v stones v stony-irons   Iron meteorites : Predominantly Ni-Fe alloys Minor amounts of other minerals such as troilite (FeS) Types classified according to % Ni: Hexahedrite octahedrite (has Widmanstatten structure, exsolution feature formed by slow cooling) ataxite   Stone meteorites : Chiefly silicates, mostly ferromagnesian Up to 1/4 metallic Ni-Fe   Types: Chondrites Achondrites   Chondrites : Contain chondrules (BB-si
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Basics of the Earth

  The Earth has evolved (changed) throughout its history, and will continue to evolve. 􀁺 The Earth is about 4.6 billion years old, human beings have been around for only the past 2 million years. 􀁻 Thus, mankind has been witness to only 0.043% of Earth history. 􀁻 The first multi-celled organisms appeared about 700 million years ago. Thus, organisms have only been witness to about 15% of Earth's history. The Earth has a radius of about 6371 km, although it is about 22 km larger at equator than at poles. Density, (mass/volume), Temperature, and Pressure increase with depth.   Internal Structure of the Earth:   Earth has layered structure. Layering can be viewed in two different ways: 1. Layers of different chemical composition 2. Layers of differing physical properties.   Compositional Layering   􀁻 Crust - variable thickness and composition 􀂄 Continental 10 - 70 km thick - "granitic" (made mostly of Oxygen and Silicon) in Composition
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DARWAR SUPER GROUP

  DARWAR SUPER GROUP  THE ARCHAEN ROCK SYSTEM – DARWAR SUPER GROUP THEY ARE BEST DEVELOPED IN SITSES OF KARNATAKA AND THE ADJOINING   STATES THE SEDIMENTARY OF THE DARWAR GROUP ARE DEPOSITED IN THE BASEMENT OF THE ”FUNDAMENTAL GNEISSES COMPLEX ” LITHOLOGY : ·          THE CHIEF ROCK TYPE IN THE DARWAR GROUP IS GNEISSES AND GRANITES ·          THEY COVER THE MAJOR PART OF SOUTH INDIA ·          MANY ELONGATED BELTS OF SCHISTOSE ROCKS ARE ENCLOSED WITHIN THESE ROCKS ·          THE SCHISTOSE ROCKS ARE FOLDED ISOCLINALLY AND EXHIBITED A STEEP DIP TOWARDS THE EAST CLASSIFICATION : ·          IGNEOUS INTRUSION   = (FELCITE AND PHORPYRIC GROUP , CHARNOCHITE , CHAMPIAN GNEISS , PENINSULAR GNEISSCLOSEPET GRANITE ) ·          UPPER DARWAR     = FERRUGINIOUS QUARTZITE , LIMESTONE , CONGLOMERATE , QUARTZITE , CALCARIOUS SILTS. ·          MIDDLE DARWAR   =GRANITE ROCK WITH GNEISSOSSE STRUCTURE ,QUARTZITE , CONGLOMERATE , LIMESTONE , CHLORITE SCHIST ,SERISITE SCHIST , BAN
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VOLCANO and TYPES

  VOLCANO Volcano is a landform, a mountain, where molten rocks erupt through the surface of the planet. The volcano mountain opens downwards to a pool of molten rocks underneath the surface of the earth. A volcano is a vent in the earth's crust through which Lava, Steam, ashes etc. are expelled.   The volcano eruption begins with the formation of magma in the lower section of the earth's crust. The earth's crust is made up of massive slabs called plates, which fit together like a jigsaw puzzle. The friction during the movement of plates causes earthquakes and volcanic eruptions with pressure, it travels upwards with tremendous force hitting solid rocks and other material and creates a new passage to the earth's surface. Once the magma reaches the air it is called lava   RING OF FIRE A zone along the edge of Pacific Ocean that has many Volcanoes and Earthquakes. The horseshoe shaped 40,000 kilometre long belt is characterized by higher volcanic activity. The Rin
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