![Page 1: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/1.jpg)
Volcanoes• Forms when magma reaches the Earths
surface and erupts as lava or ash
![Page 2: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/2.jpg)
Volcano Formation-Melting occurs in asthenosphere-Magma is lava underground-Magma is less dense than surrounding rock-rises to lithosphere and creates cracks in the solid rock-cracks are how magma reaches surface
![Page 3: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/3.jpg)
Plate Boundaries• Eruptions on plate boundaries that separate,
collide, or are hot spots
![Page 4: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/4.jpg)
Convergent Plate Boundaries-most volcanoes are at plate boundaries around the Pacific at subduction zones- this is the Ring of Fire
![Page 5: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/5.jpg)
Divergent Plate Boundaries- Mostly unnoticed b/c they occur under water
- One major divergent boundary that is above water is the East African Rift Valley
![Page 6: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/6.jpg)
Hot Spots- Balloon like plume- Usually NOT near plate boundaries- Stationary (non moving)- Creates island chains in the ocean (Hawaii)
![Page 7: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/7.jpg)
Lava-Magma that has reached the surface
Viscosity-measure of a fluids RESISTANCE to flow- low viscosity flows more easily (water) than high viscosity (molasses)- viscosity decreases as temp increases
![Page 8: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/8.jpg)
Chemical CompositionMafic Lava- low viscosity- Heavier elements (magnesium
and iron)- Usually quiet eruptions
Felsic Lava- High viscosity
-Lighter elements (silicon, oxygen, aluminum, potassium)
- Explosive eruptions
![Page 9: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/9.jpg)
Types of VolcanosVolcanoes are classified by their size, shape, and mineral type
Composite Cone- form at convergent boundaries- explosive eruptions- large, steep shape 1000’s of meters wide- composed of ash and lava- pyroclastic flows- a fast-moving current of hot gas and rock
![Page 10: Volcanoes Forms when magma reaches the Earths surface and erupts as lava or ash](https://reader036.vdocuments.mx/reader036/viewer/2022082817/56649e245503460f94b12f82/html5/thumbnails/10.jpg)
Shield Cone-fluid lava erupts, travels far- broad, wide, flat shape- gas poor-composed of lava-quiet eruption
Cinder Cone-high temp- gas rich- mafic-explosive, ejects cinders-smaller 100’s meter range- short eruption cycles- composed of ash