Computer Lab Differences between volcano types

1. Computer LabDifferences between volcano types

2. Review • Mantle magma: low in silica (like flour) so it is more runny • Melted Crust Magma: • More silica so it is thicker (Creates pyroclasts) • Contains water vapor because of ocean water when it subducts

3. VOLCANO: • A mountain like feature that forms from magma coming out of it. • Types of Volcanoes: • Cinder-Cone Volcano • Shield Volcanoes • Composite Volcanoes • Parts of a Volcano: Crater Cone Vent Lithosphere Magma Chamber Where magma, toxic gases, and water vapor are stored. Asthenosphere

4. Pyroclast: • Solid-like red-hot lava that comes out of a volcano when it erupts (silica rich magma) • This is a type of lava • Lava: • Melted rock found on the surface (silica rich orsilica poor) • Magma: • Melted rock below the surface (silica rich orsilica poor) • Pyroclastic Flow: • Avalanche of solid like red-hot rocks (pyroclasts). This is silica rich lava.

5. Cinder-cone volcanoes form at convergent boundaries. • The oceanic plate subducts, melts, and rises. Some water from the ocean subducts with it. • The magma melts through the tectonic plate above it forming a volcano. This is the only place the magma comes from that fuels a cinder cone. This liquid water that subducted turns into water vapor and rises to the volcano. • Magma comes from the melted crust (silica rich magma) only Core CINDER-CONE VOLCANOES (Part 1) volcanoes Ocean Oceanic Crust A Asthenosphere Convection cells 3, Oceanic crust A subducts & gets closer to the core where it is hot. It then melts, and the melted crust rises through the crust above it forming volcanoes.

6. Vent is clogged so toxic gases & water vapor cannot escape from the magma chamber. • This builds up pressure inside the volcano over time as more toxic gases & water vapor enter the chamber from the mantle. • Eventually, enough pressure builds that it will blow through the vent and out. Vent clogs because magma comes from melted crust that is silica rich (thick). Pyroclasts (thick lava) because magma comes from melted crust (silica rich) Ash & Toxic Gases CINDER-CONE VOLCANOES (Part 2) Core Clogged vent Ocean Oceanic Crust A Asthenosphere Convection cells Toxic gases & water vapor from subducting plate

7. Shield Volcanoes • The hot spot does NOT have a clogged vent because magma comes from the mantle that is silica poor (more fluid magma) • The toxic gases rise from the mantle and escape into the atmosphere • No pressure builds in the volcano • Volcano erupts when magma chamber fills up with magma (pressure from toxic gases has NO effect) • This is why they erupt more often • This is why they erupt quietly (not violently) Lava is runny because magma comes from mantle that is silica poor Core Extinct Volcano Extinct Volcano Lithosphere Asthenosphere Toxic gases

8. Melted Crust as Fuel for Volcano • Volcanoes that form at Convergent Boundaries • Cinder-Cone Volcanoes & Composite Volcanoes • This magma is silica rich so the magma is thicker which is why…the vent gets clogged • Mantle as Fuel for Volcano • Volcanoes that form at Hot Spots • Shield Volcanoes • This magma is low in silica so the which is why the vent does not clog so easily.

9. When the vent is filled with magma from melted crust material: • This magma is silica rich so the following occur: • The vent clogs • Causes toxic gases & water vapor to NOT escape • Causes pressure to build • Causes less eruptions • Causes more violent eruptions • Causes toxic gases to escape when it erupts only • Causes pyroclast lava (solid-like lava) • Causes pyroclastic flows • Causes the slope of the cone to be steeper.

10. When the vent is filled with magma from the mantle/asthenosphere: • This magma is silica poor so the following occur: • The vent does NOT clog as easily (or as much) • Causes toxic gases to escape all the time • Causes NO or very little pressure to buildup • Causes more eruptions • Causes quiet eruptions (no/little pressure) • Causes lava to be more liquid like • Causes the slope of the cone to be gradual

11. Usually, Vent clogs because magma comes from melted crust solidifying in vent which is silica rich • toxic gases & water vapor cannot escape so pressure builds. • Volcano explodes • Pyroclast lava released (magma from melted crust that is silica rich) Ash & Toxic Gases 4. STRATO (COMPOSITE) VOLCANOES (pt 1) Pyroclasts because magma comes from melted crust that is silica rich Core Clogged vent Ocean Oceanic Crust A Mantle Convection cells Toxic gases and water vapor

12. Sometimesmagma comes from the melted crust (silica rich). This causes… • Vent to clog & erupt like a cinder-cone with pyroclasts, ash, explosion, etc. • Sometimesmagma comes from the mantle which is silica poor. This causes … • Vent does NOT clog & it erupts like a shield volcano(runny lava, quietly, etc.) COMPOSITE VOLCANOES (Part 2) Lava is released Core Ocean Oceanic Crust A Asthenosphere Convection cells

13. CINDER-CONE VOLCANO REVIEW: • Forms at a convergent boundary • Releases pyroclastswhen they erupt (no runny lava) • Steepsided cone • The vent gets cloggedvery easily • Toxic gasesare released all at once (during an eruption) • Explosiveeruptions • Magma comes from the melted crust only • Silica rich magma that is thicker • Have pyroclastic flows • Can have mud flows (lahars) • Ash in atmosphere can lower temperature of region & block sunlight

14. SHIELD VOLCANO: • Forms at a hot spot in the middle of a plate • Releases lava when they erupt (no pyroclasts) • gradual sidedcone • The vent does NOT gets clogged • Toxic gases are released slowly over time • Quiet eruptions • Fluid lava flows • No mud flows (lahars) • No ash • Silica poor magma(fluid lava) • Magma comes from the mantle • Example Volcano … Mauna Loa in Hawaii

15. COMPOSITE VOLCANO: • Forms at a convergent boundary • Switches between getting: • magma from the mantle (silica poor magma) • subducted oceanic crust (usually from here) which is silica rich magma • Switches between these two: • Releases a type of lava called a pyroclast when they erupt (lava that is thicker-solid like) – when magma is from subducted oceanic crust • lava that is more liquid like - when magma comes from the mantle

16. COMPOSITE VOLCANO: • Fairly Steepsided cone due to switching between the following: • When lava comes from mantle the cone becomes less steep (fluid lava) • When lava comes from the melted oceanic crust the cone becomes more steep (silica rich lava) • Switches: • Vent clogswhen magma comes from the silica rich oceanic crust • Vent doesn’t clog as muchwhen magma comes from the silica poor mantle

17. COMPOSITE VOLCANO: • Switches: • Toxic gases are released all at once (during an eruption) when magma comes from the silica rich oceanic crust • Toxic gases are released slowly over time (daily or weekly) when magma comes from the silica poor mantle • Switches: • Explosive eruptions when magma comes from the silica rich oceanic crust • Non-Explosive (quiet) eruptions when magma comes from the silica poor mantle • Have pyroclastic flows & mud flows (lahars) when magma comes from the melted oceanic crust that is silica rich • Ash in atmosphere can lower temperature of region & block sunlight when eruptions are silica rich lava from the melted oceanic crust