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EARTH SCIENCE ROCK CYCLE Can be classified in two ways: 1. Origin and formation 2. Texture - Each classification has unique characteristics. - Rocks may change into different classifications under the right conditions. Definition: A rock is a naturally occurring aggregate or combination...

EARTH SCIENCE ROCK CYCLE Can be classified in two ways: 1. Origin and formation 2. Texture - Each classification has unique characteristics. - Rocks may change into different classifications under the right conditions. Definition: A rock is a naturally occurring aggregate or combination of minerals and mineraloids. Such as fossils and glass. Just as minerals are the building blocks of rocks, rocks are natural building blocks of the Earth’s lithosphere. KEY IDEAS: - Earth’s lithosphere is made primarily of rocks containing one or more minerals. - Rocks are constantly being transformed, generated, and destroyed in a process called the rock cycle. - Depending on their origin or formation, rocks can be categorized into one of three types: igneous, sedimentary, and metamorphic. PROCESS AND PRODUCT OF THE ROCK CYCLE PROCESSES PRODUCT Melting Magma Crystallization Igneous Rock Uplift and exposure Weathering and Erosion Sediments Transportation Deposition Sedimentary Rocks Lithification Metamorphism Metamorphic Rocks Formation of Igneous Rocks The term ‘Igneous’ is in fact derived from the Latin word ‘igneus’ meaning ‘fire’. They are the ‘new’ rocks on earth. It is formed through the cooling magma or lava. Magma or lava may be solidified in one of three ways: Cases: Below the surface, from a clow cooling magma – rocks formed have good crystallization (coarse-grained) and become plutonic rocks or intrusive igneous such as granite, diorite, and syenite. On the surface, from fast cooling lava – rocks formed have no visible crystals (fine-grained); may become volcanic rocks or extrusive igneous, such as basalt and andesite. On the surface, from consolidation of particles erupted by explosive volcanic activity – may become pyroclastic rocks like ignimbrite, scoria, and pumice. TYPES OF ROCKS: IGNEOUS ROCKS Types of Igneous Rocks: 1. Intrusive (plutonic) rocks 2. Extrusive (volcanic) rocks Igneous Rocks Classifying Igneous Rocks Properties & Characteristics: Dense, hard, and crystalline flow structures with no layers; not affected by chemical corrosion. Granite Basalt Andesite Gabbro Obsidian Diorite Scoria TYPES OF IGNEOUS ROCKS: Intrusive or Plutonic Rocks Form from slowly-cooled magma. TEXTURE PHANERITIC PEGMATITIC Greek phaneros, meaning “visible”. Large Minerals crystallized slowly at depth. mineral crystals that are visible without the Composed of very large crystals. aid of a magnifying lens. TYPES OF IGNEOUS ROCKS: Extrusive or Volcanic Rocks Form from rapidly-cooled magma. TEXTURE APHANITIC VESICULA Greek aphaneros, meaning “invisible”. Result of gases escaping while the volcanic Grains are too small to see with the eyes. rock is being formed.. COLOR INDEX LIGHT COLORS DARK COLORS White, light gray, tan, and pink) (black and brown) Felsic composition rich in silica (SiO2) Mafic or Ultramafic composition rich in iron and magnesium. HOWEVER: some rocks do not follow the color index. Obsidian Most obsidian is felsic composition but will typically have a very dark color. It is a volcanic glass which erupts as a lava flow. Dunite Has ultramafic composition but greenish in color because it is composed almost entirely of green mineral, olivine. TYPES OF ROCKS: SEDIMENTARY ROCKS Types of Sedimentary Rocks: 1. Clastic - when they form from lithification of rock and fragments. Ex: Breccia and Sandstone 2. Crystalline - when they precipitate out of solution. Ex: Limestone and Rock Salt 3. Bioclastic - when they are formed from the accumulation of organic material or biologic activity. May contain remnants of plants, corals, shell, or fossil fragments. Ex: Coal Formation of Sedimentary Rocks Sedimentary Rocks are a combination of a product of weathering and erosion, and organic materials. These materials are accumulated on the Earth’s surface through a process called DEPOSITION. Fossils are known to be found in sedimentary rocks. Process involved in the formation of sedimentary rocks: Lithification - Particles of sand, pebbles, and other fragments of materials called sediments, accumulate in layers and over a long period of time harden into rocks. Involves compaction and cementation. 1. Compaction- Due to the increased pressure of layered sediments, the sediments are their layers bind together. Waterborne sediments become so tightly squeezed together that most of the water is pushed out. 2. Cementation - is where new minerals stick the grains together.It’s like cement (i.e., in construction) binds gravel and sand to form walls, ceilings, or floors. Properties & Characteristics Crumbles easily, can be scratched by fingernails; grainy texture due to layers of sand, silt or gravel; varying sizes of crystals. Examples: Conglomerate Breccia Sandstone Shale Limestone Chert Rock Salt TYPES OF ROCKS: METAMORPHIC ROCKS 1. Heat 2. Pressure Types of Metamorphic Rocks: 1. Slaty - minerals are microscopic, the rock may not appear foliated. The foliation will manifest itself physically in the rock’s tendency to separate along parallel planes. 2. Phyllitic - minerals are barely visible. Their alignment results in an obvious but not clearly defined foliation. 3. Schistose - minerals are visible to the naked eye. Their layering is distinct. Usually composed of chlorite, graphite, biotite, and muscovite. 4. Gneissic - minerals are visible and elongated. The rock exhibits a coarsely branded appearance due to alignment of minerals like amphibole, feldspar, and quartz. Formation of Metamorphic Rocks These are formed from exposure of sedimentary or igneous rocks to high pressure, high temperature, or both, deep within the Earth’s surface. This process is also known as METAMORPHISM. This process affects the mineralogy texture of the rock. Metamorphisms often progress incrementally, from slight changes (low-grade metamorphism) to substantial changes (high-grade metamorphism). TEXTURE FOLIATED CRYSTALLINE - The dominant agent is PRESSURE. - The dominant agent id HEAT - Platy or elongated minerals align themselves parallel to the axis of pressure, resulting in a layered appearance or foliation. Examples: Slate, Phyllite, Schist, Gneiss MINERALS Minerals in everyday Life: Aluminum in beverage cans. Copper in electrical wires. Gold in jewelries. Graphite in pencils. Talc in make-ups Quartz as a source of silicon for computer chips. List of Minerals: Diamond Emerald Gold Snowflakes Graphite Silver Table Salt Granite Quartz CHARACTERISTICS OF MINERALS Criterion 1 NATURALLY OCCURING The substance must be naturally occurring on Earth. Minerals form through natural geologic processes. Steel and synthetic diamonds are made artificially. Thus, it is not a mineral. Criterion 2 INORGANIC Minerals are limited to substances formed through inorganic processes, and exclude materials derived from living organisms. Coal is composed of the remains of plants. Thus, it is not a mineral. Criterion 3 SOLID All liquids and gases – even those that are naturally formed such as petroleum - are not considered minerals. Ice formed in glaciers is considered a mineral but water is not.. Criterion 4 DEFINITE CHEMICAL COMPOSITION It should express the exact chemical formula with the elements and compounds in specific ratios. The only exception is the atomic substitution, which is a characteristic of certain minerals. Criterion 5 ORDERED INTERNAL STRUCTURE It should express the exact chemical formula with the elements and compounds in specific rotation. The only exception is the atomic substitution, which is a characteristic of certain minerals. Substances that fulfill all the requirements but do not have ordered internal structure are called MINERALS. Physical and Chemical Properties of Rock Forming Minerals Composition of Minerals Composition of Minerals In terms of composition, minerals can be classified into several classes which are mainly composed of elements that are abundant on Earth’s crust. Silicate Silicon and Oxygen Ex: Olyvine and Quartz Oxides Metal cations bonded to oxygen anions Ex: Magnetite Sulfide Sulfur Metal cation bonded to sulfide (s^2-) Ex: Galena Sulfates Metal cation bonded to SO4^2- anionic group Ex: Gypsum Halicides Composed of halogen ion, such as chlorine or fluorine Ex: Fluorite Carbonates Carbonic ion (CO3^2-) which bonds elements such as calcium or magnesium Ex: Calcite Native Metals Consist of single metal such as copper and gold. Ex: Gold Crystal Structure of Minerals Crystal Structure- is dependent on the chemical composition of the mineral.  CRYSTAL STRUCTURE Isometric Pyrite Tetragonal Wulfenite Orthorhombic Topaz Monoclinic Gypsum Triclinic Microline Physical Properties of Minerals Luster- describes the appearance of light as it is reflected off its surface. Metallic Luster Nonmetallic luster Terms Used to Describe Luster of Nonmetallic Minerals Luster Meanings Example Minerals Vitreous Having a glassy appearance Quarts, tourmaline Resinous Having the appearance or resin Sphalerite, sulfur Greasy Reflecting light to give a play colors; similar Chlorite, nepheline to oil on water Silky Having surfaces appearing to be composed Chrysotile (asbestos), of fine fibers gypsum Adamantine Having a bright brilliant appearance similar Diamond, cerussite to that of diamonds Pearly Appearing iridescent, similar to pearls or Muscovite, talc some seashells Dull Not reflecting significant amounts of light or Kaolinite (clay), niter showing play of colors Mineral Breakage Cleavage The tendency of a material to split or cleave along planes of weakness. Cleavage refers to the way some minerals break along certain lines of weakness in their structure. Number of Shape Sketch Direction of Sample Cleavage Cleavage Directions 1 Flat sheets Muscovite 2 at 90° Elongated form Feldspar with rectangle cross section (prism) 2 not 90° Elongated form Hornblende with parallelogram cross section (prism) 3 at 90° Cube Halite 3 not 90° Rhombohedron Calcite 4 Octahedron Fluorite Fracture Minerals having chemical bonds that are equally, or nearly equally, strong in all directions exhibit a property called fracture. Types of Fracture: 1. Irregular Fracture - when mineral fracture, most produce uneven surface and are described as exhibiting irregular fracture. 2. Conchoidal Fracture - However, some minerals, including quartz, sometimes break into smooth, curved surfaces resembling broken glass. Such breaks are called conchoidal fractures. 3. Other Types - Still other minerals exhibit fractures that produce splinters or fibers referred to as splintery fracture and fibrous fracture, respectively. Crystal Form and Habit Minerals have definite composition, it forms a definite structure which crystallizes into a specific crystal form. The outward appearance of the mineral’s crystal form is its habit. Color Most conspicuous characteristics but ambiguous and misleading. Many minerals may have the similar color, while a mineral can have different colors due to impurities. Streak Color of mineral in its powdered form. Streak Plate Used to determine the streak of a mineral by rubbing it on an abrasive ceramic tile. Hardness Measurement of the strength of the chemical bonds in its structure. Mohs Scale of Hardness Relative measure of hardness using common materials and standard minerals to represent a specific hardness value. Specific Gravity Measure of the density of a mineral. Weight of a mineral relative to the weight of an equal volume of water. Most common minerals have a specific gravity of 2.7, while gold has 19. Synthesis The rock cycle is the process of the transformation and generation of igneous, sedimentary, and metamorphic rocks. These rocks and minerals are studied according to their physical and chemical properties such as luster, color and streak, hardness, cleavage and fracture, and specific gravity. Understanding the structure and formation of rocks provides clues to the Earth’s internal processes and history.