1. VOLCANOES A brief introduction
“this area needs some excitement… time to erupt!”

2. Ashfall stymies European airlines Eruption of Eyjafjallajökull in Iceland, 2010

3. First of all, just what is a volcano?
“A volcano is a burning mountain from whose top comes smoke and fire.”
or this one:
“A volcano is a cone-shaped mountain and at the top you can see the creator smoking.”
[once this was someone’s answer on a test…….crater = creator ?]

4. “Lava flows run fast. They are very vicious.” [meant “viscous”[
Want to see some more interesting word choices about volcanoes? Sure you do!…
“Dormant volcanoes may show sins of steam, but extinct volcanoes show no sins of life.” [meant to say “signs”]
“Lava flows run fast. They are very vicious.” [meant “viscous”[
My favorite: “Cascade volcanoes were created primarily by the seduction of the Pacific Ocean plate.” [meant “subduction”]
“HI THERE, you big strong PLATE ! ”

5. Let’s analyze that first definition.
Burning - no
Mountain-usually
Summit Activity - not always
Smoke - no
Fire - no

6. Now let’s go for a more accurate definition!
A volcano :
Is the place or opening from which molten rock and gases issue from beneath the earth’s interior onto the surface, and
The hill or mountain built up around the opening by accumulation of the rock materials.

7. We could say a volcano is always a liquid rock plumbing system which extends from several 10's of kilometers depth up to the earth's surface, and includes the near- vent deposits of eruptions.
But then it quickly gets more interesting…….

8. Is this a volcano?
“Ice volcanoes commonly occur during the winter months along the north shore of Lake Superior. Cones begin to form at the leading edge of the ice shelf as it builds out into the lake. When the waves, driven by strong onshore winds, feel bottom they build and break onto the ice shelf. After the ice shelf has built out, waves continue to travel underneath the ice and are forced up through cracks and previously formed cones.” The water freezes into a cone-shaped “volcano”.

9. How about this?
Piparo is a mud volcano in Trinidad.
“The term "mud-volcano" generally is applied to a more or less violent eruption or surface extrusion of watery mud or clay which almost invariably is accompanied by methane gas, and which commonly tends to build up a solid mud or clay deposit around its orifice which may have a conical or volcano-like shape.”

10. Now let’s get to looking at more conventional volcanoes!

11. Volcanic materials range from all liquid, such as this fluid “pahoehoe” in basalt….

12. …and A’a, a more viscous lava appearance...
“Why are we running? A’a doesn’t move that fast!”
…and A’a, a more viscous lava appearance...
(Note the difference between “viscous” and “vicious”
..lava might be very viscous but is not really vicious)

13. ….to all solid and gas, such as in this
pyroclastic flow (we wouldn’t want to be there, or we would become crispy critters real quickly!)

14. Here is a video of frazil ice, which has an uncanny similarity to a fluid lava flow in terms of flow properties.
Frazil ice in Yosemite National Park, CA

15. This “fossil football” is a “volcanic bomb.”
They don’t explode on impact like incendiary bombs as depicted in the dreadfully-inaccurate movie Volcano ( 1997).

16. Volcanoes come in all shapes and sizes,
and there are reasons for the variety.

17. The largest is a shield volcano, made almost entirely of highly fluid basalt lava flows.

18. Most of the famous volcanoes in the Cascade Range are composite cones (a.k.a. stratovolcano)

19. Composite cones are made of both lava flows and fragmental material (pyroclastics).

20. Volcanoes often occur in clusters.
Loihi Seamount should be a future Hawaiian island (but hold off on making reservations….it will be several thousand years)

21. Types of Volcanic Hazards
Lava flows: Kilauea (300 homes destroyed)
Pyroclastic flows and surges: Mont Pelee, 1902 (28,000 killed)
Ash fall: Pinatubo; Eyjafjallajökull
Debris avalanches: Mt. St. Helens; Shasta
Lahars: Mt. Rainier; Nevado del Ruiz (23,000 killed)
Gas: Lake Nyos, 1986 (1700 killed from CO2)
Tsunamis: Krakatau, 1883 (36,000 killed)

22. Lava flows: Basalt is the most fluid (least viscous) and flows furthest and fastest.
This flow buried the store in Kalapana, Hawaii. Images are on April 23, June 6, and June

23. Other compositions of lava (andesite, dacite, rhyolite) are too viscous to flow very far and form short thick flows or domes, such as the two domes here at Mt. St. Helens.

24. Mount St. Helens' crater and dome as seen from the east
Mount St. Helens' crater and dome as seen from the east. New growth is on the left and the older dome is on the right. USGS Photo. taken on 3/11/05.

25. The “great white whale” is part of the new dome. MtStH, 6/24/05

26. Gas: Lake Nyos, Cameroon, Africa, in 1986 released a toxic cloud of CO2 which killed 1700 people and all animals within a 15 mile radius. CO2 is heavier than air, so it flows to lower levels once released.

27. Ash plume from Mt. St. Helens is drifting east-northeast after reaching approximately 36,000 feet above sea level. 3/8/05

28. Ash plume strongly directed by wind, with ash falling out. 3/8/05

29. Ashfall over former Clark Air Base in the Phillipines
Ashfall over former Clark Air Base in the Phillipines. Pinatubo eruption, 1991.

30. Pyroclastic. flows:. hot, fast, dense. =. deadly
Pyroclastic flows: hot, fast, dense = deadly! (Merapi, Indonesia) Can also occur due to dome collapse (Unzen, Japan)

31. August 7, 1980 pyroclastic flow on top of July 22, 1980 pyroclastic flow. USGS Photo taken on 9/30/80.

32. Lahar from Mt. St. Helens, May 18, 1980 Strongly channeled by valley!

33. A lahar (the dark deposit on the snow) flowed from the crater into the North Fork Toutle River valley. Part of the lahar entered Spirit Lake (lower left corner) but most of the flow went west down the Toutle River, eventually reaching the Cowlitz River, 50 miles downstream. 3/8/82.

34. Debris avalanches=large landslides

35. Coldwater Lake, which formed by debris avalanche raising N
Coldwater Lake, which formed by debris avalanche raising N.Fork of Toutle R. valley and damming Coldwater Creek.

36. Dome, before rockfall off the spine
Dome, before rockfall off the spine. USGS Photograph taken on May 12, 2005

37. Mt. St. Helens dome after a large rockfall event.

38. The rockfall continues….

39. After rockfall off the spine
After rockfall off the spine. Note missing piece…a big bite out of a dacite cookie.

40. You can see why the “spine” partially collapsed…it’s f-r-a-g-i-l-e!

41. Which of the events are more common and more dangerous in VALLEYS?
Here’s the list again
Lava flows
Gas
Ash fall
Pyroclastic flow
Lahars (mudflows)
Debris avalanches

43. Miscellaneous Volcanic Stuff

44. Northwest volcanic areas

45. Mt. St. Helens progression of events

46. Mt. St. Helens - before May 18, 1980

47. Mt. St. Helens - during May 18, 1980

48. Mt. St. Helens - after May 18, 1980

49. Crater Lake is amazing….

50. Sequence of events forming Crater Lake

51. Map of tectonic plates. Most volcanoes form near plate boundaries.

52. Zones of volcanism related to plate tectonics

53. Plate tectonics: a convergent plate boundary.

54. Cascade Volcanoes

55. Geyser eruption: resting stage

56. Geyser eruption: pressure is building

57. Geyser eruption: “thar she blows!”

58. Climate and volcanoes

59. A tale of two volcanic eruptions
With drastically different results

60. Mont Pelée vs. Soufrière Hills Volcano
Caribbean island of Martinique.
May 8, 1902 explosive eruption.
Searing gas and ash of a pyroclastic flow killed all but two of the 28,000 inhabitants of St. Pierre.
Caribbean island of Montserrat
December 26,1997 explosive eruption.
Searing gas and ash of pyroclastic flow killed NO humans in city of Plymouth.

61. St. Pierre after Mont Pelée eruption, 1902

62. Soufriere Hills Volcano

63. Why was there such a drastic difference in outcome from two very similar eruptions?

64. Soufrière Hills Volcano had given warning…
Which HAD BEEN properly interpreted by volcanologists…
So that Plymouth had been evacuated….
Saving thousands of lives.
Montserrat image
Mont Pelée had given warning…
Which had NOT been heeded….
So that St. Pierre had NOT been evacuated….
Costing thousands of lives.
St. Pierre images

65. A Review of Volcanic Hazards
You have learned about most of these hazards.
As we study a few of the individual Cascade volcanoes, ask:
Are any hazards especially prominent?
Are any hazards likely to be rare or absent?

66. That’s all, folks!