Bellringer

1. Bellringer • Watch this video

2. Objectives • Complete Tsunami questions with one partner • Begin volcano video and questions

3. Tsunami Questions • Complete your own • Work with a partner if you want

4. Volcanoes

5. NOVA Video: Deadliest Volcanoes • What triggers volcanic eruptions? • What is an ash cloud and how can it impact the world? • How is Yellowstone a super volcano if it’s not on a plate boundary? • How are cosmic rays used to investigate volcanoes? • Why is the ground in Naples moving up? • What can the different volcanic gases tell us about upcoming volcanic eruptions? • What is a “Lahar”, how are they created, and why are they dangerous? • Can we do anything but hope these dangerous volcanoes don’t erupt soon?

6. Bellringer • What is one technique scientists use to tell if a volcano is going to erupt soon or not?

7. Objectives • Know where and why volcanoes form. • Know the different features and types of volcanoes.

8. Grades/Time Left • Tsunami Questions • Volcano quiz • Final exam is next Thursday, 6/5 (20%) • 50MC questions • Open notebook • Astronomy (quiz?) • Safety Video Due 6/13

9. Safety Video • Groups of up to 4 • Nothing illegal • 4 minutes (including intro, video, outtakes, and credits) • Printed list of proper safety procedures

10. Volcano • A rupture on the crust which allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

11. Where do they come from? • Generally found on convergent and divergent plate boundaries. • Also found at “hot spots”, located above mantle plumes. • Where magma rises to the surface

12. Mantle Plumes

13. Divergent Plate Boundaries • Thin crust from the spreading boundary • Release in pressure • Magma rises and forms new rock

14. Mid Atlantic Ridge • The center of the ridge is new rock from rising magma • Not a line of typical volcanoes • “Black Smokers”: Deep sea vents where the magma rises and cools to become ocean floor • Iceland is part of the ridge that is above sea level.

15. Mid Atlantic Ridge

16. Black Smokers • https://www.youtube.com/watch?v=y6iK19xaYJg

17. Convergent Plate Boundaries • Usually between an oceanic plate and a continental plate • The oceanic plate becomes magma as it is run over by the continental plate • This magma tends to be very viscous and cools at depth before reaching the surface • When it does reach the surface it creates a volcano

18. Ring of Fire • https://www.youtube.com/watch?v=It7107ELQvY

19. Hotspots • Name given to areas believed to be formed by mantle plumes. • Columns of hot material rising from the core-mantle boundary in a fixed space

20. Hawaii • https://www.youtube.com/watch?v=g7OTVUY_PdQ • Start 3:40

21. Checkpoint • What are three different examples of where volcanic activity can be found? • Do they all have typical volcanoes?

22. Volcano Features • Volcanoes are described by their different features.

23. Fissure Vents • Volcanic fissure vents are flat, linear cracks through which lava emerges. • https://www.youtube.com/watch?v=VG3YunIcZ54

24. Lava Domes • Built by slow eruptions of highly viscous lava • They are sometimes formed within the crater of a previous volcanic eruption (Mt. St. Helen) • Can produce violent, explosive eruptions • Generally lava does not flow far from the originating vent.

25. Lava Dome

26. Types of Volcanoes • Shield • Cinder Cone • Composite (Stratovolcanoes)

27. Bellringer

28. Objectives

29. Shield Volcanoes • Broad shield-like profile • Formed by the eruption of low-viscosity lava that can flow a great distance from a vent. • Generally don’t explode catastrophically • Hawaii is a chain of shield cones • Common in Iceland as well

30. Shield Volcanoes

31. Cinder Cone • Result from eruptions of small cinders • Short-lived eruptions • Produce a cone-shaped hill 30 to 400 meters high • Most only erupt once • May for off side of larger volcanoes • Based on satellite images they might occur on other terrestrial bodies in our solar system

32. Cinder Cones

33. Composite Volcanoes (Stratovolcanoes) • Tall conical mountains composed of lava flows and other ejecta in alternate layers. • Different layers are made of cinders, ash, and lava. • Cinders and ash pile on top of each other, lava flows on top of the ash, where it cools and hardens, and then the process repeats.

34. Strato/Composite Volcanoes • Greater pressure build up than shield volcanoes from the underlying lava flow • More powerful eruptions from fissure vents and cones • Steeper than shield volcanoes • Ash produced from these have posed the greatest volcanic hazard to civilizations.

35. Strato/Composite Volcanoes

36. Other Types of Volcanoes • Supervolcanoes • Submarine Volcanoes • Subglacial Volcanoes

37. Checkpoint • What are the three main types of volcanoes? • Which is the worst?

38. Erupted Material • Another way of classifying volcanoes is by the composition of lava • Lava can be broadly classified into 4 different compositions.

39. Felsic Lava • Erupted magma contains >63% of silica • Highly viscous (not very fluid) • Trap gases which cause violent eruptions

40. Intermediate Lava • Erupted magma contains 52-63% silica • Generally occur above subduction zones • Typically formed at convergent boundaries • Intermediate because the magma is a mixing between felsic and mafic magmas.

41. Mafic Lava • Erupted magma contains 45-52% silica • Tend to be hotter and less viscous than felsic lavas. • Occur in a wide range of settings: • Mid-ocean ridges • Shield volcanoes • Continental flood basalts (eruptions where lava covers a very large area)

42. Ultramafic Lava • Erupted magma contains <45% silica • Very rare, has only happened a few times in the past 550 million years • Hottest laves, even more fluid than common mafic lavas

43. Checkpoint • What are the four types of lava? • What determines which type of lava a sample is?

44. Sampling Lava • Two ways • Smart Way: Wait for it to cool, pick it up, bring it to a lab for testing. • Not So Smart Way: Get it while it’s hot! • https://www.youtube.com/watch?v=egEGaBXG3Kg • http://petapixel.com/2014/05/28/swimming-fire-bts-video-qa-two-daredevil-lava-photographers/

45. Volcanic Activity • A popular way of classifying volcanoes is by their frequency of eruption. • Active • Dormant • Extinct

46. Active Volcanoes • Erupt frequently • No agreement among scientists about this • Volcanoes that are erupting or show signs that it is likely to erupt • About 1,500 active volcanoes in the world • About 50 of these erupt each year • An estimated 500 million people live near active volcanoes

47. The Most Active Volcanoes • Kilauea, the famous Hawaiian volcano, has been in continuous eruption for thirty years, and has the longest-observed lava lake. • Mount Etna and nearby Stromboli, two Mediterranean volcanoes in almost continuous eruption since antiquity.

48. Dormant Volcanoes • Volcanoes that have erupted in recorded history, but show no activity now are dormant or inactive. • Can become active seemingly out of the blue.

49. Famous Dormant Volcanoes • Vesuvius is the most infamous dormant volcano. • Yellowstone never erupted in recorded history, but we can know its recharge period is around 700,000 years. • Dormant volcanoes tend to have a worse effect on civilizations because people are surprised when they erupt.

50. Extinct Volcanoes • Considered to be very unlikely to erupt again because the volcano no longer has a magma supply. • The smaller Hawaiian islands are extinct because they are no longer above the hot spot that supplies the fresh magma. • Supervolcanoes sit on massive magma supplies that can stay hot for millions of years, so many scientists won’t consider them extinct.