1. Unit 6: Earth Shaped from the Outside in
Cycle 18: Volcanism & earthquakes
Cycle 19: Plate Tectonics
Cycle 20: Weathering & Erosion

2. Connection to last unit…
To deeply understand the processes that create rocks and minerals such as volcanism, weathering, pressue, etc. need more information about where in the world these things happen

3. Connections beyond… Why learn it? So inherently cool!
So dangerous, need to be prepared
So relevent, in the news eery day impacting people around the world

4. Class Opener Do mapping activity
Are all the earthquakes and volcanoes evenly spaced randomly across earth’s surface?
Why do earthquakes and volcanoes occur where they do?

8. Volcanoes &Volcanism
Volcanoes=the cone structure volcanism=movement of magma out of the earth
Volcanism is caused by solid rock melting. Liquid rock is less dense and therefor rises
Review: kinetic molecular theory of matter

9. What 3 things cause rock to melt and rise?
Increasing temperature
Adding water
Decreasing pressure

10. Convergent Subduction Plate
Boundary Volcanism
Divergent Plate
Boundary Volcanism
Along plate boundaries & intra-plate areas
Ring of Fire
Mid-Ocean Ridge
Hot Spots
Volcanic Arcs
Intra-Plate
Volcanism (hotspots)

11. Convergent Subduction Volcanism
Plates are colliding with each other and subducting. lithosphere is being melted
Volcanism due to increased temps, water
Divergent Volcanism
Plates are ripping apart
Volcanism due to melting of asthenosphere due to less pressure from above
Intraplate Hotspot Volcanism
In middle of plates
Hot spot in mantle
plume rises towards the surface due to density difference

13. Volcanic Structures Shield Composite Cinder
As eruptive materials pile up at an opening a “volcano” forms
Shield
Composite
Cinder

14. Shield Volcano Shield Volcanco -Low angle slopes of 1-10
Largest volcano
-Hawaii, Iceland
-Generally on ocean floor
-”quiet” eruption
-made of basalt lava flows, no ash or pyroclastics
-basaltic magma, low gas trapping 14

15. Composite Cone/Stratovolcano
Steeper slopes 10-25, taller than cinder cones. Smaller in height and width than shield volcanoes
Cascades (Mt. St. Helens), Andes
Volcanoes on continents over ocean-land subduction zones
Alternating Explosive/quiet eruptions
Built up by alternating layers of lava and pyroclastics
Built over tens to hundreds of thousands of years
Andesitic (or Granitic) composition magma, gas rich 15

16. Cinder Cones
Smallest volcanic features have large craters with steep slopes of 30-40
Paricutin, Mexico
Generally forms on continents
Explosive eruptions
Built of pyroclastics (tephra/cinders) not lava flows.
Generally short lived eruptions - weeks to a few years until the magma is degassed, then it solidifies in the pipe and flows form from the base
Paricutin, Mexico, cinder cone soon after its birth in 1943 in a Mexican cornfield. 16

17. What determines the shape, eruption type…
What determines what kind of volcano forms?
The eruptive materials (lava vs. pyroclastics)
What determines what kind of eruptive materials occur?
Type of eruption (explosive vs. quiet)
What determines what kind of eruption occurs?
The amount of pressure build up from trapped gas especially
What determines the gas content and composition of the magma?
What type of rocks are being melted, ocean floor, continental, both, asthenosphere, LOCATION

18. Warning signs of impending eruption
Earthquakes increase in frequency and strength
Ash and gas increases
Bulging of volcano side

19. Dangers Pyroclastics: breathing, hit by it
Lahars/mudflows: concrete flood
Poisenous hot gases: can’t breath
Pyroclastic flows: instant incineration
700km/hr (450mph)

20. Deaths