1. Types of Volcanoes and Volcanic Hazards
Earth and Space Science

2. Types of Volcanoes 1. Shield volcanoes
- Lava flows a great distance before having a chance to cool
- Forms a very broad volcano with gentle sloping sides as more lava flows over previously cooled lava
Types of Volcanoes

3. Shield volcanoes

4. Types of Volcanoes 2. Composite cone
- explosive and violent eruptions as pressure builds up in the sticky/gooey/viscous magma, and the lava oozes out or ash and cinders shoot out from vents
- forms layers of lava and ash
- tall with steep sides due to the lack of ability of the lava to flow very far

5. Composite cone

6. Types of Volcanoes 3. Cinder cone - magma with a lot of trapped gases
- violent eruptions that shoot out lava and ash at the same time
- this lava and ash cools as it falls and forms very steep sides to the volcano
- generally short lived volcanoes and become dormant soon

7. Cinder cone

8. Types of Volcanoes 4. Caldera
- a volcanic vent which collapsed after the erupting magma left an empty chamber under the ground
forms a large depression or hole, usually larger than the
original vent

9. Caldera

10. Volcanic Hazards
There are many materials that escape from erupting volcanoes.

11. Volcanic Flow Hazards 1. Lava flows
Streams of molten rock that comes from vents and fissures in the Earth’s crust

12. Lava flows
They destroy almost everything in their path

13. Lava flows
Factors affecting flow rate: slope of the hill, viscosity, cooling rate of the lava
 as lava cools it becomes more viscous
and less able to flow

14. Lava flows
The outer crust cools quickly and lava can still flow through it like a tube

15. Volcanic Flow Hazards 2. Pyroclastic Flows
High-density mixtures of hot ash, rock fragments, and hot gases that rush down the sides of volcanoes

16. Pyroclastic Flows
Occur in explosive eruptions

17. Pyroclastic Flows
Can move at speeds up to 350 km/h

18. Pyroclastic Flows
Extremely dangerous and destroy almost everything in their path

19. Volcanic Flow Hazards 3. Lahar
A wet, cement-like mixture of water, mud and volcanic rock fragments that flows down the slopes of a volcano

20. Lahar
Can carry rock debris ranging from clay to gravel to boulders

21. Lahar
May be triggered by eruptions melting snow and ice, and/or releasing a small lake and the water mixing with the eruption debris

22. Lahar
Rain soaked debris may also start a lahar during or after an eruption

23. Lahar
Lahars can bury entire villages under meters of mud

24. Volcanic Airborne Releases
Tephra – all pieces of volcanic rock and ash that are ejected in the air

25. Volcanic Airborne Releases
 Classified by size
- Volcanic bombs – pieces bigger than 64 mm

26. Volcanic Airborne Releases
 Classified by size
- Lapilli – pieces between 64 mm and 2 mm

27. Volcanic Airborne Releases
Classified by size
- Ash – pieces smaller than 2 mm

28. Volcanic Airborne Releases
Volcanic bombs and lapilli usually fall on or near the top of the volcano due to their size, while ash can travel hundreds to thousands of kilometers