1. VOLCANOES

2. Anatomy of a Volcano

3. Volcano “Life-cycle”
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

4. Mount Baker - dormant
Mt. Rainier - active
Shiprock Peak- Extinct

5. LAVA vs MAGMA what’s the difference?
magma: molten rock inside the Earth lava: magma that has emerged on the Earth’s surface
magma
lava

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

7. Low viscosity magmas allow gases to escape easily and move easily through cracks.
In higher viscosity lavas, gas pressures build up and erupt explosively.
Which of the volcanic eruptions (2 slides ago) likely had high viscosity lavas?

8. Which volcanoes below have high viscosity magma/lava
Which volcanoes below have high viscosity magma/lava? (CIRCLE YOUR CHOICES)

9. What causes molten rock to be viscous or not?
TWO THINGS
Silica
The higher the silica content, the higher the viscosity.
Temperature
The hotter the magma, the less viscous it is.

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

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

12. - usually non-explosive eruptions - results in lava flows & sometimes lava tubes: caves left behind after lava flows - found in Hawaii (Mt. Kilauea) and Iceland

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

14. 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

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

16. Example: 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

17. Where are volcanoes?

18. Plate Boundaries! Ring of Fire
Where are volcanoes?
Plate Boundaries!
Ring of Fire
Area of the world where volcanoes are common
Outlines the Pacific Ocean

20. hot spot: area of volcanic activity independent of lithospheric plates (meaning…they don’t move) ex. Hawaii

21. In MOTION!

22. Other volcanic features!
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

23. 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!

24. Volcanic Hazards Primary Effects Secondary Effects Lava flows
Pyroclastic activity
Ash fall
Poisonous gas
Lateral Blast
Secondary Effects
Lahar

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

26. 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)

27. 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

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

29. - CO2, carbon monoxide, sulfur dioxide, and hydrogen sulfide
Poisonous Gases
- CO2, carbon monoxide, sulfur dioxide, and hydrogen sulfide
- can cause acid rain; contaminates water supply and vegetation
FURTHEST WE GOT IN 3RD BLOCK.

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

31. Predicting Volcanoes (5 factors used)
1. Monitoring of Seismic Activity- often the earliest sign
2. Thermal monitoring - measuring ground temperatures

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

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