1. Lecture 5 Volcanism

2. Lecture Outline ICharacteristics of Volcanoes IITypes of Volcanoes A)Shield Volcanoes i.Description ii.Composition iii.Eruption Features B)Composite Volcanoes i.Description ii.Composition iii.Eruption Features iv.Distribution C)Cinder Cones i.Description ii.Composition iii.Eruption Features IIILava Floods IVSubmarine Eruptions VLiving with Volcanoes VIConclusions Physical Geology

3. Characteristics of Volcanoes Vent Fumarole Crater Caldera Volcanic Domes Physical Geology

4. vent : the opening at the earth's surface through which volcanic materials are extruded. fumarole : a hole or vent from which volcanic fumes or vapors issue. Characteristics of Volcanoes Vents and Fumaroles Physical Geology

5. Mt Poas, Coast Rica Mt Erebus, Antarctica Halemaumau, Hawaii crater : a basin-like rimmed structure at the top or on the flanks of a volcanic cone; it is formed by explosion or collapse Characteristics of Volcanoes Craters Physical Geology

6. caldera : a large basin-shaped volcanic depression, more or less circular. the diameter of which is many times greater than that of the included vent or vents, irrespective of the steepness of the walls or the form of the floor. Aniakchak, Alaska Kaguyak, Alaska Crater Lake, Oregon Characteristics of Volcanoes Calderas Physical Geology

7. Characteristics of Volcanoes Caldera Formation Physical Geology

8. volcanic (lava) dome: steep-sided mound built by magma too viscous to flow far from vent before crystallizing and cooling. Characteristics of Volcanoes Volcanic Dome Physical Geology

9. Shield Volcanoes Composite Volcanoes Cinder Cones Types of Volcanoes Physical Geology

10. Mauna Loa, Hawaii Slope: Gentle (2-10 o ) Height: up to 10 km Composition: Flow layers Basaltic Eruption: Effusive Low-Viscosity Lava A'a Pahoehoe Flank Eruptions Other Characteristics: Lava Ponds and Tubes Spatter Cones Types of Volcanoes Shield Volcanoes Physical Geology

11. Types of Volcanoes Shield Volcanoes Physical Geology

12. a'a pahoehoe Types of Volcanoes Shield Volcanoes Physical Geology

13. spatter cone: A low steep-sided cone of spatter built by lava fountains along a fissure or around a vent lava tube : a hollow space beneath the surface of a solidified lava flow, formed by the withdrawal of molten lava after the formation of a surficial crust Types of Volcanoes Shield Volcanoes Physical Geology

14. Mt St Helens and Mt Ranier Slope: < 33 o Height: 1000 - 4000 m Composition: Layers of pyroclastic fragments Andesitic Eruption: Explosive Other Characteristics: Magma blocks conduit Glowing clouds and lava flows Types of Volcanoes Composite Volcanoes Physical Geology

15. Mount St. Helens May 18, 1980 Types of Volcanoes Composite Volcanoes Physical Geology 8:33:20 a.m. The blast is over but the mountain begins to pulverize as the eruption vents its full fury, sending a thick, 3- mile-wide ash cloud 80,000 feet into the sky. 8:33:00 a.m. A cubic mile of mountain gives way, traveling at 70 to 150 mph, and superheated rocks in the volcano's core are suddenly exposed, shooting a lateral blast of gas north, incinerating everything in its path. Huge glaciers on the mountain's peak melt instantly. 8:32:10 a.m. A 5.1 magnitude earthquake about 1 mile beneath the mountain causes the north flank to slide. Tendrils of steam burst from the mountain, releasing pressure bottled up in magma below. 8:32:00 a.m. The bulging north flank that geoscientists had watched develop since March is intact. It had clearly grown by 450 feet in some areas, and by late April was estimated to be growing at five feet a day. http://seattlepi.nwsource.com/mountsthelens/grapherupt.shtml

16. Types of Volcanoes Composite Volcanoes Physical Geology

17. Types of Volcanoes Composite Volcanoes Physical Geology http://www.3dnworld.com

18. Types of Volcanoes Composite Volcanoes Physical Geology

19. Paricutin, Mexico Slope: Steep (33 o ) Height: < 300 m Composition: Pyroclastic fragments Various Eruption: Explosive Other Characteristics: Short-lived Cinder Cone,Mauna Kea, Hawaii Types of Volcanoes Cinder Cones Physical Geology

20. Lava Floods Physical Geology

21. Lava Floods The Columbia Plateau Physical Geology

22. Kavachi, Solomon Islands Submarine Eruptions Physical Geology

23. Submarine Eruptions The Mid-Ocean Ridge Physical Geology

24. Volcanic Hazards Physical Geology