Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Quiz Question • Do you expect that the earthquake in Hawaii was: – Tensionsal (pull-apart movement) – Compressional (push-together movement) – Shear (moving-past movement) • Given the geologic setting of Hawaii, why do you expect this? Where does continental crust come from? Continental Crust What defines a specific mineral? Crystal structure and Chemical Composition Mineral Name Chemical Composition Crystal structure Quartz SiO2 Al2O3 C C Framework Silicate Corundum Diamond Graphite 3-D framework Sheets The Silicate Minerals Basic Building Block Silicate ion: SiO4-4 One Si surrounded by 4 O in a tetrahedron. Can be combined in different ways: •Isolated tetrahedra •Chains •Sheets •3-D Framework Isolated Chains Tetrahedra Sheets Framework Silicates In framework silicates, every O is shared with two Si tetrahedra: Quartz: SiO2 Rocks, some context • What is a rock? – A coherent, natural, aggregate of minerals (or glass) • Types of rocks – Igneous - formed from melt – Sedimentary - formed by surface processes – Metamorphic - formed by transforming other rocks Let there be… magma • Where is magma formed? In the lithosphere Plate Boundaries – – – – – At subduction zones (addition of water) At midocean ridges (decompression) At rifts (decompression) At hot spots (decompression) In next to other magma (contact) Solid material rises Pressure decreases Decompression melting Surface Hot Spot Vulcanism Addition of volatiles (water and CO2) Contact Melting Where are Igneous Rocks Formed? Intrusive (Plutonic) vs. Extrusive (Volcanic) Rocks What is a Metamorphic Rock • Metamorphic rocks are formed by metamorphism of other rocks – Changes in physical, chemical, and mineralogical characteristics – In Solid State Metamorphism • What causes rocks to metamorphose? – – – – Heat (different mineral stability, faster reactions) Hot water (addition/removal of elements) Confining Pressure (different mineral stability) Directional forces due to deformation Kinds of Metamorphism • Contact Metamorphism with hot rocks Kinds of Metamorphism • Burial Metamorphism of Sediments (think isostacy! And then think geotherm!) Kinds of Metamorphism • Regional Metamorphism from mountain building Where do Metamorphic Rocks Form? Weathering • The conversion of solid rock to smaller pieces or other (non-rock-forming) minerals • Physical v. Chemical weathering (they work together!) Physical weathering • … the process whereby large rocks are broken into smaller rocks. • Many different processes Chemical Weathering • Dissolution = dissolving salt in water • Hydrolysis 2 KAlSi3O8 + 2 H2CO3 + H2O Al2Si2O5(OH)4 + 4SiO2 + 2K+ + 2HCO3• Oxidation (where does the Fe+2 come from?) 4 Fe+2 + 3 O2 2 (Fe+3)2O3 • The role of organisms Transport (erosion) • What transports sediments? – Water, primarily – Wind • Why? – Ultimately, for water: gravity Sedimentary Rocks • • • • Sediments: layers of loose particles that originate from the weathering of the continents (solid debris or dissolved substances) Sedimentary Rocks: Rocks formed from sediments by the process of lithification. Two types – Clastic Sediments – Chemical and Biochemical Sediments Requirements – Weathering – Erosion – Deposition – Lithification Sedimentary Environments Principal of Original Horizontality and the The Law of Superposition Sediments (and sedimentary rocks) record conditions on the (local) earth’s surface at the time they were formed. 1000 mya 600 mya 600-240 mya 420 mya 370 mya 270 mya 180 mya