1. Continuation of earth’s process part 2

3. Volcanoes
Mountains that form when layers of lava and volcanic ash erupt an build up
Most of the Earth’s volcanoes are dormant

4. Volcanoes
Deep in the Earth, rocks melt to form magma, and is called lava when it flows out into the surface through opennings called vents (the openning at the top is called the crater)
These magma cools forming layers of rocks (igneous)

7. Volcanic Ejecta
Pahoehoe
Pillow Lava
Lava Tunnel Aa

8. Pyroclast
Volcanic materials ejected primarily made up of rocks, dust and gases

9. Where Do Volcanoes Occur?
Divergent Boundaries
Rifts are long, deep cracks in between plates that separate
Magma flows on rifts as lava and is instantly cooled by sea water
Lava builds up from the sea floor and volcanoes rise above sea level, forming islands

10. Where Do Volcanoes Occur?
Convergent Boundaries
Magma that is created from the subduction zone works it way to the surface forming volcanoes

11. Where Do Volcanoes Occur?
Hot Spots
Areas not on plate boundaries
Some areas in the mantle are hotter than other areas
Hotspots melt rocks which then rises toward the crust as magma

12. Factors that Affect Eruptions
Amount of water vapor ang other gases trapped in the magma
Rock composition of magma (basaltic or granitic)
Basaltic magma – contains little silica, very fluid, and produces quiet, non explosive eruptions
Granitic magma – contains lots of silica, has high water content, very thick, and produces violent and explosive eruptions

13. Major Types of Volcanoes
1. Shield Volcano
With broad, shield-like profiles, are formed by the eruption of low-viscosity lava (basaltic) that can flow a great distance from a vent, but not generally explode catastrophically.
More common in oceanic than continental settings.

14. Mauna Loa, Hawaii

15. 2. Cinder Cone or Scoria Cone Volcano
Once lava is thrown into the air, it cools and hardens (tephra)
When it falls, it forms a steep-sided, loosly consolidated cinder cone volcano

16. Paricutin Volcano, Mexico

18. 3. Composite Volcano
Formed from an alternating layer of tephra and lava

19. Mt. Fuji, Japan

20. Mayon Volcano, Philippines

21. Other Types of Volcanoes
Flat, linear cracks through which lava emerges

22. Lakagigar fissure vent, Iceland
Krafla Volcano, Iceland

23. After the explosion of a volcano, its top colapses down into the vent forming a very large opening called a caldera

25. Taal Volcano, Philippines