Lecture 17 volcanoes

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Today: Chapter 9: The Wrath of Vulcan Volcanic Eruptions Term Break Extra Credit due this Friday by end of lecture Today’s Lecture: Chapter Volcanic activity Basic types of eruptions Anatomy of a volcano Materials erupted Classes of volcanoes Basaltic volcanoes Intermediate volcanoes Silicic volcanoes Volcanic hazards Case Study: Mt Saint Helens Types of Volcanic Eruptions Fig 09.09ab W W Norton Central Eruption Fissure Eruption Basic Anatomy of a Volcano Fig 09.10 W W Norton HY DROTHERMA L DEPOSITS A S REPOSITORIES FOR GEOLOGIC INFORMA TION  Most terrestrial hydrothermal systems are sustained by magmatic heat sources  Variations in the temperature (and density) of fluids drives convective circulation in the crust, producing large-scale transfers of energy and materials  As hot fluids move through the crust, they interact chemically with their host rocks, leaving behind distinctive geochemical, and mineralogical signatures Materials extruded during an eruption Volcanoes erupt: ◆ Lava ◆ Gases ◆ Pyroclastics Fragmented rock, ash & dust Ash and tephra Explosive eruption Volcanic bombs Side vent Eroded cone Lava cone Sills p.248-249a Mud flows (older) Pyroclastic flow (nuée ardente) Sequential ash and lava layers Lava flow Dikes Fracturing original artwork by Gary Hincks Cinder cones Lava pavement (cracked/broken) Old lava dome Lavas Sedimentary rocks Laccolith Metamorphic rocks Chimney Contact metamorphism Granite intrusion (older/cold) Magma chamber Fig 09.24 W W Norton Case study: Mt St Helens 9500’ ● Ejected nearly a cubic kilometer of ash & rock debris ● 59 deaths 8150’ ● Ash blown over 11 miles high! (1350’ shorter!) Fig 09.15 W W Norton Fig 09.16abc W W Norton Fig 09.22e Photo by J Marso, U.S Geological Survey Volcanic mudflows Mount Saint Helens A lava dome formed in crater after major eruption GENERA L FEA TURES OF HY DROTHERMA L SY STEMS Hydrothermal Systems:  Develop anywhere that fluids coexist with a heat source  Typical heat source a magma intrusion  Effects: Alteration of adjacent rocks and deposition of mineral deposits, often of economic importance  Also a source of geothermal energy Grand Prismatic Spring Videos: Types of Volcanic Eruptions 1: Lava flows 2: Ash falls 3: Ash flows 4: Mud flows VENUS Volcanoes Elsewhere in Solar System MARS Fig 09.30a JPL / NASA Olympus Mons: Largest Volcano in the Solar System Olympus Mons, Mars Jupiter’s moon “Io” From Scientific American, Feb 2000 ● Jupiter’s moon “Io” Volcanic Eruptions in Progress on Io Fig 09.30b JPL / NASA [...]... of gas in magma Can increase fluidity Fluidity Let’s look in more detail at: a Shield volcanoes b Cinder cones c Composite cones ◆ low profile ◆ broad base ◆ basaltic lavas ◆ flows are thin ◆ travel far from source Most basaltic volcanic activity: Ocean ridges O Ocean ridge in the Pacific a a Shield Shield volcanoes volcanoes b b Cinder Cinder cones cones Example: Hawaii c c Composite Composite cones...volcanic pipe/neck after erosion before erosion Shiprock, NM Fig 09.04a Stephen Marshak Fig 09.04b Stephen Marshak Volcanologists recognize 3 general volcano types: a Shield volcanoes b Composite cones c Cinder cones Types of Volcanoes 9 km 150 km Shield volcano (e.g Hawaii) 3 km p.248-249c 15 km original artwork by Gary Hincks Composite volcano (e.g Vesuvius) 0.3 km 1.5 km Cinder cone (e.g Sunset
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