GEOL 108Lg 1st Edition Lecture 9Outline of Last LectureI. Volcanic Hazardsa. Pyroclastic Flows, Ash Clouds, EtcOutline of Current LectureI. The Rock Cycle: Igneous, Sedimentary and Metamorphic II. The Wilson Cycle: Opening and Closing of Ocean Basins III. Intro to MineralsCurrent LectureRock C yc le IThere are three ways rock can be created on earth – this being so, there are three main classifications of rock, based on the three processes - igneous, sedimentary, and metamorphic.I g n e ou s r o ck s : formed by molten liquid minerals that lie beneath the earth's crustal layer. They're formed by cooling magma beneath the earth's surface (intrusive formation) – cooling lava upon the surface (extrusive formation).Intrusive igneous rock formation can a really long time (up to thousands of years) to cool of. This being so, igneous rock that cool slowly will contain larger mineral crystals than faster cooling igneous rocks. Volcanic obsidian is an example of a quickly cooling rock, and is both smooth and contains small crystals. This is caused by extrusive lava from volcanoes/surface fissures.All rocks on earth were originally igneous. This is the ONLY way that entirely new rocks can be made.Most of the rocks of the earth's crust are igneous although sedimentary rocks usually cover them.Basalt is the most common type of igneous rock.Se d im e nt ary r o ck s : formed through the lithification of existing rock or fossils. Rocks areeroded and become tiny particles. These are then transported and deposited along with otherpieces of rock called sediments.Sediments are cemented together and compacted and hardened over time by the weight and pressure of up to thousands of feet of additional sediments above them. Eventually, sediments are lithified entirely and become solid sedimentary rock. These sediments that come together are known as clastic sediments.IMPORTANT TERM: lithification is the process or processes by which unconsolidated materials are converted into coherent solid rock as by compaction or cementation.Metamorphic RockMetamorphic rocks (rock that changes form): formed by applying large amounts of pressure and temperature to existing rock converting it into a new type of rock. All rock types, even metamorphic rocks, can be modified into metamorphic rocks.Metamorphic rocks are created, again, by extreme pressure such as under many thousands of feet of bedrock or through being crushed between tectonic plates. Sedimentary rocks can become metamorphic rocks sediments above them apply enough heat and pressure to change the rock’sMetamorphic rocks are more resistant to weathering and erosion. Why? Because they’re harder. Tectonic Rock Cycle: Form new oceanic crust at spreading center - trench - subducted, melted- form new continental crustRock banding or foliation (stripes in the rock) is caused by the grouping of specific minerals within the rock forming parallel bands or layering that are perpendicular to the pressure that causes them. Banding structure (found in high grade metamorphic) means that it was modified a lot.Wilson CycleThe Wilson cycle is the process of opening and closing of ocean basins caused by tectonic movement. The Wilson cycle begins with a rising magma plume and then the crust begins to thin. As the crust keeps thinning ( extensional tectonic forces), an ocean forms and sediments accumulate along the margins. Then, subduction is initiated on one of the ocean basin's margins and the ocean basin closes up. When the crust begins to thin again, another Wilson Cycle begins.If we start out here with an intact continent—first, we form new seafloor—break continent apart - new ocean after spreading is initiated - passive margin -->subduction zone— supercontinental break up and assemblyTethyan Trench was an ancient oceanic trench that existed in the northern part of the Tethys Ocean during the middle Mesozoic to early Cenozoic eras and disappeared due to the Wilson Cycle.Continental Accretion - continents grow by addition of new continental material around a“nucleus”Planetary Rock Cycle ReviewImportance of Rocks and Minerals•Fundamental building blocks of Earth•Various uses for modern economic developments•Important clues for figuring out the history of Earth•Knowledge of minerals and rocks as the first important step to better manage Earth’sresources•Important to our health and environmentBasic Chemistry Review•All mater, including minerals and rocks, made of atoms•Atom structure: Nucleus (proton and neutron) and surrounding electrons•Atomic number: The unique number of protons in an element’s nucleus•Atomic mass number: The sum of the member of protons and neutronsBasic Chemistry Review , Contd.•Ion: Charged atom particles, reactions between different types of atoms•Isotopes: Atoms of the same element with varied number of neutrons•Chemical bonding–Ionic bonds (electrostatic between ions, NaCl)–Covalent bonds (shared electrons between atoms, H2)–Metallic bonding (shared electron density across lattice) (gold, for example - very fixed crystal struture - distributed electron cloud - makes metals very conductive)–van der Waals bond (attraction between molecules – dipolar nature - )WHAT IS A MINERAL?•Naturally occurring•Non-organic•Characteristic chemical composition•Distinctive physical propertiesSymmetry of the crystals also helps you to tell apart different mineral typesRocks: Made out of different mineralsImportant to note: when you form a rock it depends on where you are and its climate - mountain vs. desert, for example.•Crystalline structureRock-Forming Mineral Groups•More than 4,000 minerals, but a few dozen are common on or near Earth’s surface•Common mineral groups are primarily classified by chemical composition•Silicates: Contain Si-O tetrahedron fundamental building unit, including the two most abundant elements oxygen (O) and silicon (Si) in the Earth crust. The most abundant mineral group•Carbonates: contain containing the carbonate ion CO32-•Oxides: Contain oxygen atoms bonded to an atom of another element•Sulfides: Contain sulfur atoms bonded to one or more metallic elements•Native elements: Made of single elementMineral Diagnostic Properties•Color and streak•Luster•Crystal form•Cleavage•Hardness•Special properties (taste, smell, feel, reaction to acid, magnetism)The most important