1. Volcanoes in our Community Volcanic Hazards: Airborne Problems Science Std: Geo # 3f

2. When a volcano erupts……  It forms one of 2 main types of volcanic cones A Composite Cone A Shield Cone But only one of these types is a problem for airborne debris

3. A Composite Volcano The explosive eruptions typically occur only along volcanic island arcs and continental margins because magma generated in subduction zones is higher in silica than basaltic magmas generated beneath mid-ocean ridges and at hot spots.

4. But what can come out?  The first problem you get for a large eruption  Is a pyroclastic flow

5. But what can come out?  All of the material that can come out is called tephra  It comes in many sizes  Big boulders  Smaller rocks  Ash and gases  Depending on the size, they can travel a short distance or a long ways

6. A closer look….. When a volcano erupts many things come out

7. A closer look….. The largest rocks land close They can be the size of cars and are called lava bombs

8. A closer look….. Smaller rocks get carried by the wind farther away These are the size of pebbles and are called lapilli

9. A closer look….. The ash from the eruption goes the farthest distance Miles and miles away

10. A closer look….. The larger ash falls fairly close by The small ash can travel around the world

11. Which is the worst?  Even though the large lava bombs are dangerous  The ash that falls causes the most damage  Ash is very rough is like sandpaper

12. What is volcanic ash?  Small jagged pieces of rocks, minerals, and volcanic glass the size of sand and silt  Volcanic ash is hard, does not dissolve in water  is extremely abrasive and mildly corrosive, and conducts electricity when wet.

13. Some Effects of Volcanic Ash When volcanic ash accumulates on buildings, its weight can cause roofs to collapse, killing and injuring people A dry layer of ash 4 inches thick weighs 120 to 200 pounds per square yard

14. Some Effects of Volcanic Ash Volcanic ash can cause internal-combustion engines to stall by clogging air filters Engines of jet aircraft have suddenly failed after flying through clouds of even thinly dispersed ash

15. Some Effects of Volcanic Ash Agriculture can also be affected by volcanic ash fall Crop damage can range from negligible to severe, depending on the thickness of ash, type and maturity of plants, and timing of subsequent rainfall

16. Some Effects of Volcanic Ash Volcanic ash poses a health risk If ash gets into your lungs, it can turn into cement and make it very hard to breathe

17. Where can the ash go? The ash goes where the wind blows A large eruption can put ash 5 miles into the air The ash from one place can cover many states

18. Where can the ash go? The ash from Mt. St. Helens eruption landed in 10 states Video

19. Where can the ash go? Mt Pinatubo in the Philippines erupted in 1990 and was 10x bigger than the Mt. St. Helens eruption

20. Where can the ash go? If Yellowstone erupts, it will be 300x bigger than Mt. St. Helens and the ash can cover half of the United States