1. 3 Basic Volcanic “Products”: 1. LAVA: Aa (flows like pile of black gravel)

2. 3 Basic Volcanic “Products”: 1. LAVA: Pahoehoe (flows like water) Pahoehoe Lava Flow Smooth and…

3. “Rope-like!”

4. 2. PYROCLASTS: Dust (very fine- travels far) Ash (Sand) Cinders (Gravel) Blocks/Bombs (Big Stuff) 3 Basic Volcanic “Products”: Broken pieces of volcano rock…

5. Pyroclasts

7. 3. GASES Water 3 Basic Volcanic “Products”: Sulfur Dioxide Carbon Dioxide (Carbonated!)

8. Sulfur Vent Gases: Sulfur may be mined right from volcanic craters!

9. Why Do Volcanoes Erupt Differently? It’s all in the Magma! The Eruption Type varies with the VISCOSITY of the Magma. That’s how “sticky” it is!

10. The VISCOSITY varies with: TEMPERATURE (the hotter, the more fluid!) COMPOSITION

11. Intermediate silica… STICKY Low silica… FLOWS LIKE WATER COMPOSITION High silica… VERY STICKY!

12. AMOUNT OF DISSOLVED GASES The more gas – the more explosive! (particularly if the lava is high silica) Low silica LAVA + GAS = lava fountains

13. 2 BASIC TYPES OF VOLCANOES: “QUIET” ERUPTIONS: fast moving lava flows BASALT SHIELD VOLCANOES ARE FOUND PREDOMINANTLY AT RIFTS AND HOT SPOTS BASALT MAGMA SHIELD VOLCANOES 1: Low Silica Magma:

14. Ridge or Rise BASALT SHIELD VOLCANOES ARE FOUND PREDOMINANTLY AT RIFTS AND HOT SPOTS

15. …Slowly grow by multiple thin layers of fluid lava. Shield Volcanoes

16. Lava Fountain. Basalt (low silica) lava flows easily, and can erupt hundreds of feet into the air.

17. Hawaiian Shield Volcano

18. Galapagos Islands-Shield Volcanoes

19. ANDESITE MAGMA: ANDESITE STRATOVOLCANOS NEAR SUBDUCTION ZONES STRATOVOLCANOES (COMPOSITE) ‘Sticky Lava’ (EXPLOSIVE ERUPTIONS) 2 BASIC TYPES OF VOLCANOS: 1: Intermediate Silica Magma:

20. ANDESITE STRATOVOLCANOS NEAR SUBDUCTION ZONES Trench Strato Volcanoes!

21. Strato Volcanoes …grow violently by explosive eruptions and domes of sticky lava..

22. Stratovolcano (composite)

23. Cinder Cone

24. CALDERAS: FORMED BY COLLAPSE OF LARGE AREAS YELLOWSTONE PARK HIGH-SILICA ERUPTION… VERY STICKY MAGMA BIG!!!

25. Caldera Yellowstone!

26. Eruption Threats: Lava: Lava is usually NOT a threat to Humans. Shield Volcano: Fast-moving lava StratoVolcano: Slow-moving lava

27. Eruption Threats: Gases: Gases may be poisonous… Gases may simply displace oxygen… Heavier Gases collect in low spots…

28. Eruption Threats: Pyroclastics Vast layers of pyroclastic material cover EVERYTHING! Pyroclastics kill vegetation… Pyroclastics collapse roofs… Pyroclastics suffocate and bury Humans.

29. Eruption Threats: Pyroclastic Flow (Nuee Ardente) A superheated blast of gas and pyroclastic material… Tend to follow valleys CAN climb hills and cross water! Can smash everything in its path.

30. This is what they look like… …coming right at you!

31. The aftermath… a former forest.

32. Eruption Threats: LAHAR DEVASTATING mud flow… Confined to valleys… Can travel for MILES… Can smash everything in its path.

33. Lahar eroding river bank

34. Here is an example! 5,000 years ago… 500 years ago… Anyone want to move to Orting?

35. Other effects of Volcanic Eruptions: Vast amounts of volcanic dust reflect sunlight… …cooling the Earth…..and creating great Sunsets!

36. Other effects of Volcanic Eruptions: Major eruptions noticeably cool the weather… “1800 and froze to death” The eruption of Tambora in 1815… In New England, it snowed at least once in each of June, July, and August in 1816…

37. “Unexpected Results” Even old and “dead” volcanoes are dangerous collapse threats! Such avalanches can travel for MILES! A collapse at Mt. Shasta traveled more than 30 miles! Volcanoes are unstable structures!

38. The collapse of Mt. Shasta…

39. Predicting volcanic eruptions: An increase in gas outputOften causes death of vegetation… Uplift, deformation of the volcano and surrounding area… Harmonic tremors… Small, constant earthquakes (lava on the move!)

40. AND…oddly enough…a sudden CESSATION of gas output… WHY…? But… What if the crater is blocked?

41. NOW… WE have problems! But… What if the crater is blocked?

42. Famous Eruptions: The oldest historic eruption…Vesuvius Pyroclastic flows and lahars buried 3 cities… …including the famous resort city of Pompeii.

43. Famous Eruptions: Mt Pelee in1903… Scientists first recognize Pyroclastic flows! Pyroclastic flow obliterates city of St. Pierre.

44. Famous Eruptions: Nevada Del Rio… (ARMERO) Armero and 20,000+ people destroyed by Lahar… Small eruption produces BIG Lahar.

45. Famous Eruptions: CAMEROONS… (Africa) Giant “soda pop” shaken and fizzed… CO2 Gas collects at bottom of deep crater lake… More than 1000 lost…

46. Many Americans in the Pacific Northwest (California, Oregon, Washington) live with Stratovolcanoes… What do they do…? They mostly hope that nothing will happen!