1. VOLCANIC HAZARDS ASSESSMENT Human-based Data Sources Geochemical Data Geophysical Data

3. ACTIVE vs. EXTINCT VOLCANOES Historians say: Active volcanoes are those that are erupting or showing some activity now. Volcanoes that have erupted historically, but are inactive at present, are Dormant. Volcanoes that have had no activity in historical or archaeological time are Extinct.

4. ACTIVE vs. EXTINCT VOLCANOES To geologists: Active volcanoes have magma chambers Extinct volcanoes have no magma left in chambers

5. HUMAN-BASED DATA Historical Records Archaeology Oral Tradition These can help extend the record back to a few thousand years

6. GEOCHEMICAL DATA Radiometric Dates on Volcanic Materials- –Can extend dates back to millions of years –Give date of last eruption –Give repeat interval of past events –Show which types of volcanic products are expected

7. Geophysical Data are used to assess Present-day Risk Is Magma Present? Determined by S-wave activity Heat Flow, especially if increasing Earthquake Patterns -shallow concentric patterns Tilting or Bulge of Surface from GPS Data, Surveying, SAR Interferometry

8. Earthquakes in Hawaii

9. Earthquakes In Iceland

10. Interferometry: Layering two Images of separate times on top of one another to measure vertical change Top: visual spectrum shows nothing new Bottom: Interferogram measures areas of differential change due to ground swelling upward. Maximum displacement is in center and pattern is concentric, suggesting a pending volcanic eruption

11. VOLCANOES IN THE US There are 33 active volcanoes in the US Most are at convergent plate boundaries in Alaska and N. California, Oregon, and Washington. These are all stratovolcanoes, which are the most dangerous in terms of explosive activity. Some are on or near hotspots: Hawaii’s volcanoes, and Yellowstone Some are former CPB: Central and Southern California The remainder are on a failed rift (former divergent plate boundary): Arizona, New Mexico

13. VOLCANIC HAZARDS Lava flows Pyroclastics Gases –Heated air –Toxic components –Climate change Lahars Tsunamis Earthquakes

16. Volcanic Gases: 80% H 2 O, plus CO 2, SO 2, and also CO, H 2 S

17. GLOBAL COOLING DUE TO LARGE ERUPTION Ash injected into Stratosphere circulates around the world for up to 3 years

18. Lahar floods Armero, Colombia after eruption of Nevado del Ruiz

19. Krakatau, 1883 Lava and slope collapse produced a tsunami up to 40m high. -Killed 36,000 people in SE Asia -Effects of Tsunami felt 7000 miles away Ash and gases produced global cooling that lasted 3 years