PPT-1 Petrology Lecture 6 Generation of Basaltic Magma

GLY 4310 Spring 2020 2 Magma Series Definition A group of rocks that share some chemical and sometimes mineralogical characteristics They share patterns on chemical variation diagrams which suggests a genetic relationship beyond the scope of this course. Principal Types of Ocean Principal Types of Ocean Basins Basalt Basins Basalt Table 10 Table 10 Common petrographic differences between tholeiitic and alkaline Common petrographic differences between tholeiitic and alkaline basalts basalts Tholeiiti Lakshmi Planum is bordered on most sides by curved mountain belts (Maxwell, Freya, and Danu), as are some continents on Earth (e.g., North America). The mountain belts around Ishtar are compressional, Yellowstone Park is not only spectacular but also unique. It is the result of three volcanic eruptions, the likes of which have never been seen in all of recorded history. The first eruption occurred 2 million years, followed by two more eruptions 1 million years and 600,000 years ago. Below Yellowstone Park there is a hot spot that is generating basaltic magma. At the time of each of their three eruptions, the magma chamber began to produce large volumes of basaltic magma. Because of its low viscosity, the basaltic magma quickly rose to the bottom of the granitic continental crust. However, because the density of basaltic magma (density about 3) is slightly higher than that of granite (density about 2.9) it could not force its way through the granite to the surface. Instead, it began to pool beneath the granitic crust. The amount of heat trapped within the molten basaltic magma was enough to melt the minerals making up the overlaying and surrounding granite, forming a growing mass of granitic magma. Granitic magma is highly viscous and extremely gas-charged. Although it rose only very slowly, the granitic magma advanced upwards by melting even more of its own overlying granitic rock. At some point, radial fractures began to form around the rising mass of granitic magma. These fractures allowed steam eruptions to vent gas. Shortly after, with the overlying granitic rock severely weakened by the fractures, the highly gas-charged granitic magma erupted. The land to a distance of 200 miles in all directions was decimated. Pyroclastic flows, the most destructive eruptive features known, swept across the countryside. Ash fell across the country from the eruption site to the Atlantic Ocean. Ash polluted the world’s atmosphere, blocked the energy of the Sun, and plunged the Northern Hemisphere into a frozen wasteland for years. Can such an eruption occur in the Yellowstone region again? All the evidence suggests that the magma chamber below Yellowstone Park is current rising. According to the director of the Yellowstone Volcanic Observatory, it is not a question of whether or not another super-eruption CAN happen; it’s a question of WHEN it will happen!. Hot rocks/Fire Rocks. Igneous Rock . Igneous rocks form . when molten rock cools and solidifies. . Molten rock is called magma when it is below the Earth’s surface and lava when it is above.. when molten rock cools and solidifies. There are 3 types of volcanoes:. Shield – VERY large. Composite – medium. Cinder - small. Differences between volcanoes. Origin. Where does magma come from?. Shield – Basaltic magma forms deep down. Youtube. :. Volcano Eruption – The Eruption of Mount St Helens 1980. 22 minutes. VOLCANOES. . Lithosphere. Side vent. Pipe. Central vent. Lava flows. Dike. Sill. Magma. chamber. Magma, which originates in the asthenosphere.... Introduction to Metamorphism. GLY 4310 - Spring, 2016. 2. Metamorphism Definition. “The mineralogical, chemical, and structural adjustment of solid rocks to physical and chemical conditions which differ from the conditions under which the rocks in question originated” (from the Glossary of geology, 2nd edition) . Igneous Structures and . Field Relationships. GLY 4310 - Spring, 2016. 2. Viscosity and Temperature. Anhydrous rhyolitic magma . 1400. °. C - 10. 5. poise. 1000. °. C - 10. 8. poise. 3. Viscosity and Composition. Mid-Ocean Ridge Volcanism. GLY 4310 - Spring, 2016. 2. MOR System. 3. MOR Spreading Rates. 4. Oceanic Crust Cross-Section. Figure 13-5 . Modified after Brown and . Mussett. (1993) . The Inaccessible Earth: An Integrated View of Its Structure and Composition. Chapman & Hall. London.. Mid-Ocean Ridge Volcanism. GLY 4310 - Spring, 2017. 2. MOR System. 3. MOR Spreading Rates. 4. Oceanic Crust Cross-Section. Figure 13-5 . Modified after Brown and . Mussett. (1993) . The Inaccessible Earth: An Integrated View of Its Structure and Composition. Chapman & Hall. London.. Introduction to Metamorphism. GLY 4310 - Spring, 2017. 2. Metamorphism Definition. “The mineralogical, chemical, and structural adjustment of solid rocks to physical and chemical conditions which differ from the conditions under which the rocks in question originated” (from the Glossary of geology, 2nd edition) . Igneous Structures and . Field Relationships. GLY 4310 - Spring, 2017. 2. Viscosity and Temperature. Anhydrous rhyolitic magma . 1400. °. C - 10. 5. poise. 1000. °. C - 10. 8. poise. 3. Viscosity and Composition. 9.1 – How & Where do Volcanoes Form?. One of the most dramatic activities associated with plate tectonics is the eruption of a volcano.. Volcano refers to both:. The . opening. in Earth’s crust through which molten rock, gases, and ash erupt.. Margherita. . Polacci. F. . Arzilli, G. La Spina, N. Le . Gall. , . R. . Torres-. Orozco. , M. E. . Hartley. , D. Di Genova, . R. . C. . Atwood. , E. . W. . . Llewellin. , . R. . . Brooker. , H. M. .