volcanoes - quia€¦ · volcanoes • why do they form? – heat and pressure in the earth melts...
TRANSCRIPT
![Page 1: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/1.jpg)
Volcanoes
• Why do they form?
– Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface through cracks and weak spots in the crust
![Page 2: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/2.jpg)
Magma rises to the surface because it is less dense than other mantle and rock material.
When magma reaches the surface it is called lava
![Page 3: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/3.jpg)
Lava Types
• There are different types of magma
– The type depends on the kind on the minerals that make up the rock material that was melted to form the magma **(silicia).
– Three common types of magma are basaltic and granitic (andesitic, dacite and rhyolitic)
![Page 4: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/4.jpg)
Basaltic magma
– Comes from rocks in the mantle– Lowest in silica– Least viscous, flow easily
![Page 5: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/5.jpg)
Grantic Type #1 -Andesitic Magma
• Mostly from the melting of wet oceanic crustal rocks
• This occurs at subduction zones where an ocean plate goes beneath another ocean plate or a continent.
• Higher in silica, has more dissolved gasses, more viscous than basaltic lava
![Page 6: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/6.jpg)
Granitic Type #2 -Rhyolitic Magma
• Forms from melting of continental crust rocks.
• High in silica, high viscosity• Often solidifies before it reaches the
surface.
![Page 7: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/7.jpg)
Main Ideas about magma/lava
• The more silica it has, the higher the viscosity, the more explosive the volcano.
• Temperature can affect the viscosity of magma. The hotter the temperature the lower the viscosity so the faster it flows.
![Page 8: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/8.jpg)
Where do volcanoes form?
• Divergent plate boundaries• Convergent ocean to ocean subduction
zone• Convergent ocean to continent
subduction zone• Hot spots
![Page 9: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/9.jpg)
Divergent Boundaries
• Basaltic lava flows• Form large shield shaped volcanoes
from repeated layers of flowing lava
![Page 10: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/10.jpg)
Convergent boundaries• Subduction zones result in melting
ocean and continental crust• Viscous lava and higher gas content
leads to explosive eruptions
![Page 11: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/11.jpg)
Erupts large amounts of fragmented material (tephra), much of which falls back to earth forming large steep-sided volcanoes called stratovolcanoes
![Page 12: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/12.jpg)
Hotspot
• Can form anywhere. • Magma rise from deep in the mantle• Hawaii – shield volcano• Yellowstone – explosive caldera volcano
![Page 13: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/13.jpg)
Types of Volcanoes
• Shield• Cinder cone• Stratovolcano (composite)
![Page 14: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/14.jpg)
Shield Volcano
• Layers of “quiet” basaltic lava flows• Divergent boundaries, oceanic hotspots
![Page 15: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/15.jpg)
Stratovolcanoes (composite)• Andesitic/rhyolitc type magmas• Higher in silica, trapped gasses• Explosive eruptions and lava flows
![Page 16: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/16.jpg)
Cinder cone volcanoes• Most common type. Form from eruptions that
are not superexplosive.• Cinders cool while they are thrown through
the air
![Page 17: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/17.jpg)
• Occur on flanks of shield volcanoes stratovolcanoes, or in fields of smaller eruptions
![Page 18: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/18.jpg)
• They could have lava flows that occur at the base or out of the flank but not the main vent.
• Smaller than other volcanoes usually
less than 250 m high and 500 m in diameter
![Page 19: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/19.jpg)
What happens when a volcano erupts?
• Lava flows• Tephra, falling ash• Pyroclastic flows, glowing avalanches• Mud and Debris Flows (lahars)• Toxic Gasses• Tsunamis
![Page 20: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/20.jpg)
Warning signs
• Ground deformation, magma collects in magma chamber causing swelling of volcanoes slopes
• Earthquakes and tremors, especially increased activity
• Gas and Steam Emissions – especially increased activity
![Page 21: Volcanoes - Quia€¦ · Volcanoes • Why do they form? – Heat and pressure in the earth melts mantle rocks, or earth’s crust melts forming magma, which rises to the surface](https://reader030.vdocuments.us/reader030/viewer/2022041019/5ece9c22ad639c66df582b55/html5/thumbnails/21.jpg)
Picture credits• Convergent boundary http://courses.unt.edu/hwilliams/GEOG_3350/examreviews/
tectonics.htm
• Shield Volcano
http://wapi.isu.edu/EnvGeo/EG6_volcano/volcanoes.htm
• Stratovolcano
http://wapi.isu.edu/EnvGeo/EG6_volcano/volcanoes.htm
• Kiauea
http://www.freewebs.com/kilauea_16/coolpictures.htm
• Mt. St. Helens
http://epod.usra.edu/archive/images/mt_st_helens_110.jpg
• Lava Fountain
http://volcano.und.nodak.edu/vwdocs/vwlessons/landforms/part8.html
• Cinder cone
http://encarta.msn.com/media_461547396_761570122_-1_1/Cinder_Cone.html