Transcript Slide 1
CH. 10.1 The Nature of Volcanic Eruptions Roots: Dyn = energy (dynamic) Dys = bad (dysfunction) e- = away (eject) Ego = self (egotistic) Em = cover with (empower) Endo = inside (endocrine) Enn = years (perennial) En = inward (enclose) Epi = among (epidemic) Equi = equal (equivalent) 10.1 The Nature of Volcanic Eruptions May 17th 1980 Mt St Helens May 18th 1980 Mt St Helens May 19th 1980 Mt St Helens May 18th 1990 Mt St Helens Volcanoes from Every Angle Volcanoes: Some Understanding (Flash: Volcanoes Mtns of Fire 27:00) Volcanoes: Cultures (Flash: Volcano Village Pride 2:49) Volcanoes: Out There (Flash: Volcano Olympus Mons 0:50) Volcanoes: The Big One (Flash: Volcano What Are the Odds 2:52) Factors Affecting Eruptions Viscosity = a substance’s resistant to flow The viscosity of magma as it rises inside the volcano can affect the type of eruption. High Viscosity = slow moving = explosive eruptions Low Viscosity = faster moving = quieter eruptions Types of Viscosity in Lava http://www.classzone.com/books/earth_science/terc/content/visualizations/es0905/es0905p age01.cfm?chapter_no=visualization Factors Affecting Eruptions Dissolved Gases = gases trapped in magma Vent = opening to the surface Gases provide the force to eject magma from the vent. Gases are mostly water vapor and carbon dioxide (just like in a carbonated drink). High viscosity magma holds the gases until they explode out. Low viscosity magma lets the gases escape easily so they just bubble out. Volcanic Gases bubbling out. http://www.britannica.com/EBchecked/topic-video/632130/124646/Molten-sulfur-andvolcanic-gases-bubbling-out-of-an-undersea Volcanic Material Lava Flows Melted basaltic rock flows quickly (about 10-300 meters per hour). Smooth “skin” with wrinkles. Pahoehoe flow - looks like twisted and braided rope. aa flow – rough, jagged blocks with sharp edges. Melted rhyolitic rock flows very slowly. Pahoehoe Flow aa Flow Lava Flows Volcanic Material Gases Gases are held in the magma under pressure. When the pressure is released the gases escape. Common gases usually include water vapor, carbon dioxide, sulfur, nitrogen, and a little chlorine, hydrogen, and argon. Sulfur gases can be easily detected from their “rotten egg” odor. Volcanic Gases Volcanic Material Pyroclastic Materials Particles produced in volcanic eruptions. Vary in size from fine dust and ash to pieces weighing several tons. Cinders = small sized Lava blocks = large sized already hardened Lava bombs = large sized still glowing HSW: Volcanoes: Pyroclastic Flow Time: 02:29 Assignment Discovery: Pompeii's Destruction Time: 02:51 HSW: Surviving Montserrat Time: 04:04 Pyroclastic Materials Mt St Helens Anatomy of a Volcano http://www.voanews.com/ftp afp/VolcanEN1605/start.swf Ash Cloud Cinders Vent Lava Bomb Pyroclastic Cloud Crust Pyroclastic Material Conduit Magma Chamber Flank Eruption Types of Volcanoes Types of Volcanoes Produced by the accumulation of fluid basaltic lava. Broad,slightly domed structure. Examples are Hawaiian Islands and Iceland. Low amount of gases. Shield Volcanoes Oregon Hawaii California Types of Volcanoes Made of cinders that harden in the air. Steep-sided sloping structure. Examples are on Hawaiian Islands and in California. High amount of gases. Cinder Cones California Hawaii Types of Volcanoes Made of layers of lava and pyroclastic deposits. Large, symmetrical cone structure. Examples are all around the Ring of Fire. High amount of gases. Composite Cones/Stratovolcanoes Mt. Pelee, W. Indies Fujiyama, Mt Shasta, Japan CA Alaska Types of Volcanoes Dangers from Composite Cones Pyroclastic Flows Pompeii Lahars (Mudflows) Indonesia Caldera Formation: Caldera = large depression in a volcano Calderas Oregon Iceland Alaska Phillipines Volcanic Necks and Pipes Pipe = long hole through which magma moves Neck = what’s left when the outside of the pipe erodes away leaving the solidified rock inside standing. Volcanic Necks and Pipes Burma Chile Wyoming New Mexico Lava Plateaus = large, flat landforms resulting from lava flow extruding from multiple fissures. See pg 288 Fig 9B. Yellowstone Hawaii Italy Japan