Volcanoes and Earthquakes

1. Volcanoes and Earthquakes GPH 111

2. Volcanoes and Earthquakes Game Plan: • Types of eruptions and the importance of viscosity • Rock class and landform type • Dangers associated with volcanic eruptions • How earthquakes work • Earthquake danger

3. Volcanoes • Stem from the release of magma on to earth’s surface • Over 1,500 active volcanoes on the planet (75% along the Pacific Rim of Fire) • 50 to 70 volcanic eruptions every year • Powered by… Mt. Pinatubo, 1990

4. Types of Rock Erupted(igneous extrusive) • Basalt- silica content between 48% and 55% • Andesite - silica content between 55% and 60% • Rhyo-Dacite - silica content between 60% and 77% Increase in silica content, increase in viscosity. Activity Time

5. Rock Types Generate Viscous to Non-viscous flows of lava • Basalt - low silica, low viscosity (like……), mild eruptions, flow fast. • Andesite - medium silica, higher viscosity (like……), violent to explosive eruptions. • Rhyo-Dacite - high silica, high viscosity (like…….), mild eruptions to the most explosive eruptions on the planet.

6. Rock class determines landform type and eruption style: • Cinder Cones - (basalt) mildly explosive • Shield Volcanoes - (basalt) mildly explosive • Composite Volcanoes - (andesite to dacite) moderate to highly explosive • Lava Domes - (dacite to ryholite) non-explosive • Calderas- (andesite to ryholite) extremely violent and explosive

7. Constructed from fountains of lava that rain around the vent. Cinder Cones - They can also issue low volatile flows, quietly oozing from the vent. SP Crater, N. AZ Hawaii - Cinder Cone in Action “Basalt Landform”

8. Basically really big, long duration cinder cones Shield Volcanoes - Olympus Mons Mauna Loa “Basalt Landform”

9. Composite Volcanoes - Build up over time with alternating ash fallouts and lava flows, tendency to generate extremely violent events mixed with more moderate events. Mt. Fuji - classic composite cone “Andesite Landform”

10. Mt. Saint Helens Composite Volcanoes - “Andesite Landform”

11. Mt. Saint Helens Composite Volcanoes - “Andesite Landform”

12. Mt. Pinatubo Composite Volcanoes - “Andesite Landform”

13. Marianas Trench Composite Volcanoes - “Andesite Landform”

14. Highly viscous eruptions that build internally and externally Lava Domes - Lava Dome developing in Mount St. Helens Mt. Elden, N. AZ “Rhyo-Dacite Landform”

15. Highly explosive eruptions that lead to structural collapse from an emptied magma chamber Calderas- Show Movie - Crater Lake, 6 miles wide, 7,700 years ago Long Valley Caldera, 15 miles wide, rhyolitic, 760,000 years old released 160 cubic miles of material “Rhyo-Dacite Landform”

16. Yellowstone has been rising since 2006. 600,000 years ago erupted 71 cubic miles of rock Calderas- “Rhyo-Dacite Landform”

17. Dangers associated with eruptions: • Lahars a hot or cold mixture of water and rock fragments flowing up to 70 mph • Pyroclastic flows fluidized masses of rock fragments and gases that move down slope (can travel over 400 mph, and approach 2,000° F) Mt. St. Helens, 1980 Mt. St. Helens, 1980 http://www.metacafe.com/watch/119241/big_in_japan/ Mt. Pelée, 1902 http://dsc.discovery.com/videos/ultimate-guide-to-volcanoes-pyroclastic-flow.html

18. Dangers associated with eruptions: • CO2 Emissions - Release of CO2 from buried magma into the atmosphere through faults, fissures, and lakes. (Cameroon Lake Nyos, 1986) Mammoth, CA – 1,300 tons of sulphur dioxide released every day. “What might some positives be?”

19. Positives associated with Volcanism: • Fertile Soils Enriched soils from mineral rich volcanic ashfalls • Geothermal Energy Magma in the earth heats groundwater and the steam is used to power generators • New Land Lava flows from continents into oceans can generate new land for development

20. If you knew this would happen…. What would you do… How sure do you need to be?

21. Earthquakes • Detected with Seismographs (movie) • Rated based on the Richter Scale • Elastic Rebound theory (Demonstration) • Evidence and Damage from an Earthquake 3.0 on the Richter Scale represents 31.5 times more energy than a 2.0, and 992 times more than a 1.0

22. Elastic-Rebound Theory How do earthquakes work?

23. 1989 Loma Prieta Earthquake Epicenter - location at the surface Focus - actual location of maximum movement

24. Field Evidence of an Earthquake… Fault Scarps – Steplike linear landform coincident with a fault trace and caused by geologically recent slip on the fault Fissures – Cracks or ruptures on earth’s surface from earthquakes, but without offset

25. Earthquake Damage “Earthquakes don’t kill people, buildings do.” Japanese saying

26. Things to Know: • Basic volcanic rock breakdown based on silica and their viscosity • Basics associated with volcanic forms linked to the different rock types - Cinder cones, Shields, Composite Cones, Lava Domes, Calderas • That low viscosity eruptions tend to be much less violent than high viscosity eruptions and why • Dangers associated with volcanism • Positives associated with volcanism • Problems with volcanic or earthquake prediction • How Earthquakes are generated with regard to the Elastic-Rebound Theory • Field evidence associated with earthquakes Help: Chapter TL