Rocks PDF

ROCKS refers to the solid mass of lithosphere. It is a naturally occurring solid mixture of one or more different minerals and other organic matter. Petrology -the science that is concerned with the study of rocks. PROPERTIES OF ROCKS 1. Rocks exhibit different properties. (as to col...

ROCKS refers to the solid mass of lithosphere. It is a naturally occurring solid mixture of one or more different minerals and other organic matter. Petrology -the science that is concerned with the study of rocks. PROPERTIES OF ROCKS 1. Rocks exhibit different properties. (as to color, rocks may be dark, light ,reddish, gray brown, yellow, or even black. 2. Rocks differ in texture: Some are fine, others are rough. 3. Some are glossy in appearance and smooth to touch. 4. Most rocks are hard, others are brittle.  THREE CLASSIFICATIONS OF ROCKS IGNEOUS ROCK from a Latin word - “ignis” which means fire. -formed by cooling and crystallization of hot, molten rock material called magma.  Origins of Igneous Rocks Extrusive Rocks: Intrusive Rock: These rocks are formed These rocks form underground from above the ground magma. when lava flows or explodes from a volcano. Granite Basalt Obsidian Gabbro Common Igneous Rock are INTRUSIVE ROCK EXTRUSIVE ROCK BASALT GRANITE ANDESITE RHYOLITE OBSIDIAN DIORITE PUMICE ANDESITE RHYOLITE BASALT SCORIA GABBRO TUFF  Obsidian Obsidian is formed above ground and cools quickly, but it forms no crystals and has a glassy texture. Texture of Igneous Rocks Texture depends on the size and shape of the crystals when the rock forms. This is due to the cooling rate of the rocks. Rapid Cooling: Slow Cooling: Rapid cooling produces fine grains and small Slow cooling produces coarse grains with crystals. large crystals. This is associated with intrusive rocks. This is associated with extrusive rocks. Andesite Diorite IGNEOUS ROCKS CAN BE CLASSIFIED AS FOLLOW A. Fine grained igneous rocks- consist of very small crystals formed through rapid cooling at the surface of the Earth. IGNEOUS ROCKS CAN BE CLASSIFIED AS FOLLOW B. coarse-grained igneous rock-consist of large crystals and likely formed far below the surface of the Earth IGNEOUS ROCKS CAN BE CLASSIFIED AS FOLLOW C. porphyritic igneous rocks- consist of large crystals embedded on a group of smaller crystals. IGNEOUS ROCKS CAN BE CLASSIFIED AS FOLLOW D. Glassy igneous rock- formed when a molten rock is ejected by a volcano in the atmosphere causing the lava to cool instantly Mineral Composite of Igneous Rocks Low Silicates: High Silicates: Igneous rocks with low amounts of silica Igneous rocks high in silica usually appear usually produce dark colored rocks. light in color. Pumice Peridotite Types of Igneous Rocks Igneous Intrusive or Plutonic Igneous – form from magma that cools and crystallizes beneath the Earth’s surface. Granite – a light-colored igneous Gabbro – a coarse-grained, dark- rock with grains large enough to be colored, intrusive igneous rocks. It is visible with the unaided eye. It is usually black or dark green in color composed mainly of quartz and and composed mainly of the feldspar with minor amounts of minerals plagioclase and augite. It mica, amphiboles and other is the most abundant rock in the minerals. deep oceanic crust Types of Igneous Rocks Igneous Extrusive or Volcanic Igneous – form at the Earth’s surface. They cool and crystallized from magma which has spilled out onto the surface at a volcano. At the surface, the magma is more familiarly known as lava. Basalt – as a mafic Obsidian – that Scoria – a dark- is formed from colored igneous rock silicate rock is usually with abundant dark-colored, hard, lava is also dark- round bubble-like fine-grained and with colored but cavities known as high specific gravity. glassy, meaning vesicles. it has no crystal. Uses of Igneous Rocks For thousands of years people have used igneous rocks for building and tools. Obsidian has been used for tool making by Native Americans. Some surgeons use obsidian instead of steel in their scalpels Pumice is used for cleaning Granite is still used today for today because they cut better and for removing calluses from constructing buildings. and leave a thinner scar. feet.  One of the most common igneous rocks is granite. Many mountain ranges are made of granite. People use granite for countertops, buildings, monuments and statues. A. Igneous rocks are recognized by : 1. the interlocking texture of the grains; 2. the presence of vesicules (holes) in extrusive igneous rocks 3. may be dark-colored and heavy; 4. may display two grain sizes, one much larger than the other Sedimentary rocks - formed through a series of processes: erosion, deposition, compaction, and cementation. Erosion Erosion is the wearing away of rock due to wind, water or ice. Deposition Deposition is when the sediments from erosion settle out of the wind, water and ice and are left or deposited in a different place. Compaction Sediments build up over time and press down on the layers below. This squeezes the layers so that the particles or grains stick together. Cementation Minerals that are dissolved in water start to crystallize. These crystallized minerals “glue” the solids or grains together. Three Main Types of Sedimentary Rocks 1.Clastic Sedimentary Rocks – derived from mechanical weathering. -Clastic sedimentary rocks are made up of pieces (clasts) of pre- existing rocks. Chemical Sedimentary Rocks – -form when dissolved materials precipitate. -form by chemical precipitation that begins when water traveling through rock dissolves some of the minerals. 3. Organic Sedimentary Rocks -formed by the accumulated sedimentary debris caused by organic processes. -These may contain fossils of plants and animals trapped in the sediments as the rock was formed.  Organic sedimentary rocks form from the accumulation and lithification of organic debris, such as leaves, roots, and other plant or animal material. Rocks that were once swampy sediments or peat beds contain carbon and are black, soft, and fossiliferous. Examples of Sedimentary Rocks: Conglomerate is a clastic sedimentary rock that contains large (greater than two mm in diameter) rounded clasts. The space between the clasts is generally filled with similar particles and/or a chemical cement that binds the rock together. Examples of Sedimentary Rocks: Sandstone is a sedimentary rock composed of sand-size grains of mineral, rock, or organic material. Examples of Sedimentary Rocks: Shale– a fine-grained a. Limestone -is a sedimentary sedimentary rock that forms rock composed primarily of from the compaction of silt calcium carbonate (CaCO3) in and clay-size mineral particles the form of the mineral calcite. It that we commonly call “mud”. most commonly forms in clear, warm, shallow marine waters. Sedimentary Rocks are recognized by: 1. grains cemented together 2. the presence of fossils 3. light-colored and light weight 4. may display interlocking grains but is very light weight  Classification of Sedimentary Rocks  Oil, natural gas, coal, and uranium, our major energy resources, are formed in and come from sedimentary rocks. Sand and gravel for construction come from sediment. Sandstone and limestone are used for building stone. Rock gypsum is used to make plaster. Limestone is used to make cement. Salt is used for flavoring. Sandstones are economically important as major reservoirs for both petroleum and water, as building materials, and as valuable sources of metallic ores. Most significantly, they are the single most useful sedimentary rock type for deciphering Earth history.  from the words “meta” (change) and” morph” (form). It is form when a sedimentary or igneous rock is exposed to high pressure, high temperature or both deep below the surface of the earth. All types of rock can change Metamorphic rocks originally start out as different types of rocks. Because of pressure deep within the earth, they melt and change. Below are a few metamorphic changes. Granite Sandstone becomes becomes Gneiss Quartzite Shale becomes Slate Metamorphism is a process that produces fundamental change in the mineralogy and texture of the rock. Regional-due to changes in pressure and Contact-mainly by heat due to contact with temperature over large region of the crust 2 magma  REGIONAL METAMORPHISM Protolith – original rock prior to metamorphism. (slates, phyllites, mica-shists,granulites) Some common types of metamorphic rock include: Slate, Schist, Gneiss, Amphibolite, Marble, Quartzite, Meta conglomerate  TYPES OF METAMORPHIC ROCKS: Types of Metamorphic Rocks: 1.Foliated metamorphic rocks – have a layered or banded appearance that is produced by exposure to heat and directed pressure. slate– derived from shale. It is Gneiss – derived from the finest-grained foliated conglomerate. metamorphic rock. It is often contain feldspar or quartz. Foliated metamorphic rocks Phyllite –is a foliated metamorphic Schist-made up of rock that has been low pressure and plate-shaped mineral heat. Phyllite formation from slate grains that are large that is further metamorphosed so enough to see with an that very fine grained mica mineral unaided eye. archives.. 2 Non-foliated metamorphic rock – do not have a layered or banded appearance. Marble – derived from Quartzite – derived from limestone. It is a hard sandstone. It is very hard crystalline rock and is considered as the most and durable. beautiful rock because of its shimmering luster. Non-foliated metamorphic rock Anthracite-is a jet-black, AMPHIBOLITE is a non-foliated hard coal that has a high metamorphic rock that forms through recrystallization under conditions of luster, is brittle and breaks high viscosity and directed pressure with conchoidal fracture. Original Rock Intensity of Metamorphism Shale Slate – schist Rhyolite Slate, Schist Granite Schist, gneiss Basalt Amphibolite, schist Limestone Marble Sandstone Quartzite Conglomerate Metaconglomerate Classification of Metamorphic Rocks  The Rock Cycle Starts with molten material called magma found beneath the surface of the Earth. In time magma solidifies to form igneous rocks. This may occur either on the surface or beneath the ground.Igneous rocks are formed on the surface are known as extrusive or volcanic igneous rock and while those that formed beneath the ground are known intrusive igneous rock. On the surface of the Earth, igneous rocks are slowly broken down into smaller fragments known as sediments through the process of weathering. The different agents of erosion will transport down these sediments to nearby bodies of water or in the deserts. In site of deposition the sediments undergo processes like sedimentation, compaction, and cementation Some rocks remain on the surface of the Earth but if buried,they wil be subjected to great pressure and intense heat. The pressure and heat will transform the sedimentary rocks into metamorphic rocks.F urther heating and exposure to extreme pressure and temperature will turn these metamorphic rocks back into magma, which , when cooled will solidify to form igneous rock, thus repeating the cycle.  This never-ending cycle has been going on for over 4 billion years. The earth is continually breaking down and rebuilding itself.