Lecture12 volcanoes
- 1. Volcanoes
- 2. Seismogram 3 types of waves
- 3. P- waves (Primary, Compression)
- 4. S- waves (Secondary, Shear)
- 7. How do we know about the Core?
- 9. S-waves
- 10. How do we know about the Core? studies of earthquake wave reflection and velocity differentiates layers shows increase in density, pressure, & temperature w/ depth
- 11. Volcanism = when molten magma extrudes onto Earth’s surface
- 12. Types of Volcanoes Shield Volcano Stratovolcano/Composite Volcano Cinder Cone 9 km 3 km 0.3 km
- 13. Shield volcano 150 km
- 14. Hawaii Rivers of lava - very fluid Hawaii
- 15. Shield Volcanoes on Mars: Olympus Mons
- 16. Stratovolcano
- 17. Stratovolcano Alternating Layers of Lava flows & Pyroclastic deposits AKA Composite Volcano
- 18. Flows don’t go as far from vent Lava is more viscous Higher Silica (~55-65%) More volatile gases in lava Stratovolcanoes / Composite Volcanoes
- 19. Pyroclastic flows Avalanche of rock material, hot ash & gas Highly destructive Typically faster than 80km/hr and up to 700°C Can incinerate, burn, and asphyxiate people
- 20. Caldera = basin-shaped depression e.g., Crater Lake (Mount Mazama) Oregon
- 22. Cinder Cone Diamond Valley, UT Small in size Pyroclastic Material- Fall Steep Slopes
- 24. Volcanic hazards volcanic gases (H 2 O, CO 2 , sulfur oxides) pyroclastic flows = avalanche of hot gas, ash, & rock fragments lahars (mudflows) lava flows
- 26. 1902- Mt. Pelée, Martinique, Caribbean St. Pierre
- 28. After the eruption 20,000 inhabitants were killed
- 29. Mt St Helens lahars
- 30. Mt St Helens lahars
- 31. 2 Types of eruptions Effusive gentle, low viscosity lava shield volcanoes e.g., Hawaiian volcanoes Explosive violent, high viscosity lava composite volcanoes e.g., Mount St. Helens, Nevada del Ruiz, Yellowstone