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VOLCANOES.

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Presentation on theme: "VOLCANOES."— Presentation transcript:

1 VOLCANOES

2 Volcano Basics Active – a volcano that has erupted recently (geologically speaking) Dormant – (sleeping) has erupted within the past few thousand years – will likely erupt again Extinct – hasn’t erupted in 10’s of thousands of years; unlikely to erupt again

3 Mt. Rainier - active

4 Mount Baker - dormant

5 Shiprock Peak – extinct volcano

6 magma: molten rock inside the Earth lava: magma that has emerged on the Earth’s surface

7 er lava                                magma

8 What makes a Volcano Violent?

9 viscosity: a fluid’s resistance to flow high viscosity = high resistance to flow (THICK) Low viscosity = low resistance to flow (THIN) Nope…not movin’

10 You’re as slow as MOLASSES!!

11 Low viscosity magmas allow gases to escape easily and move easily through cracks.
In higher viscosity lavas, gas pressures build up and erupt explosively. VIRTUAL LAB!!

12 Viscosity is determined by silica content and temperature.

13 The higher the silica content, the higher the viscosity.
The hotter the magma, the less viscous it is.

14 1. Shield 2. Composite 3. Cinder cones
TYPES OF VOLCANOES 1. Shield 2. Composite 3. Cinder cones

15 Shield Volcanoes - largest volcanoes (tallest when measured from the ocean floor) - shaped like a gentle arch or shield basaltic lavas (low silica content)

16                                                     

17 - usually non-explosive eruptions - results in lava flows - found in Hawaii (Mt. Kilauea) and Iceland

18                                                     

19 lava tubes: caves left behind after lava flows

20                                 

21 Composite Volcanoes - coned shaped; sometimes called stratovolcanoes
- lava contains mostly andesite or rhyolite (higher silica content) - more viscous

22 Combination of explosive activity (pyroclastic) and lava flows Responsible for most deaths of any type of volcano ex. Mount Saint Helens Mt. Pinatubo Mt. Fuji Mt. Vesuvius

23 Mount Saint Helens, Washington State

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25 Mt. Saint Helens, after eruption

26 Mount Pinatubo, 1994

27 Mount Fuji, Japan                                                     

28 Mount Vesuvius / Ruins of Pompei

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30 Cinder Cones - smaller volcanoes - form quickly are active for a few years and then usually go dormant

31 Wizard Island                                                     

32 ex. Paracutin, Mexico - 1943, hole in ground
- 2 weeks prior, small tremors - 1st day grew 10 m - By 5th day it was 100 m tall - After 2 yrs, it was 400 m tall - went quiet after 9 years

33

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35 Where are volcanoes?

36 Ring of Fire Area of the world where volcanoes are common
Outlines the Pacific Ocean

37

38 hot spot: area of volcanic activity independent of lithospheric plates ex. Hawaii

39

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41 Features of Volcanoes crater - depression found at the top of a volcano; formed by the explosion of the upper portion of the cone

42 hot springs: water is heated by the hot rock and reaches Earth’s surface
geyser: heating and circulation of water forms a pattern (RARE!) ex. Old Faithful

43 Half of the 1,000 geysers in the world are in Yellowstone National Park, WY (United States)
                                

44 caldera: a giant crater that can be more than 12.5 miles in diameter
formed by rare, very violent eruptions none have occurred in recorded history (they are 1000 times more violent than Mt. St. Helens!) - Yellowstone caldera was formed 600,000 years ago!

45 Crater Lake, OR

46 Long Valley, CA

47 Aniakchak, AK                                                     

48 Primary Effects Secondary Effects
Volcanic Hazards Primary Effects Secondary Effects

49 Lava flows: eruption of magma at Earth’s surface
Lava flows vary based on the composition of the magma.

50

51

52                                 

53                                                     

54                                                     

55

56 tephra: any material that is blown out of a volcano (mostly ash)
Pyroclastic Activity: explosive volcanism where tephra is physically blown into the atmosphere tephra: any material that is blown out of a volcano (mostly ash)

57                                 

58

59 ash fall: huge quantities of rock, glass and gas are blown high into the air
- kills vegetation - contaminate water - structural damage - jet engine “flame out” - respiratory irritation

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61 lateral blast: explosions of gas and ash from the side of the volcano; destroys part of the mountain ex. Mt. St. Helens

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63 Poisonous Gases - CO2, carbon monoxide, sulfur dioxide, and hydrogen sulfide - can cause acid rain; contaminates water supply and vegetation

64                                                     

65 Secondary Effects lahar: debris flows and mudflows
volcanic debris becomes saturated with water ex. Mt. Pinatubo, Philippines

66                                                     

67 Buildings buried after lahars at Pinatubo

68 Aerial View, Pinatubo Aftermath

69 Predicting Volcanoes 1. Monitoring of Seismic Activity- often the earliest sign 2. Thermal monitoring - measuring ground temperatures

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71 3. Topographic Monitoring - mountain may tilt and swell before an eruption 4. Volcanic Gas Emissions - changes in composition of gases may indicates rising of magma

72 5. Geologic History - geologists map and date rocks around the area


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