We can start with some initial background questions about volcanism in general.

• What are the compositional variations and physical properties of lavas?
• How do you melt rocks to make magma that erupts as lava?
• What are the sources of magma?
• What are types of volcanic eruptions?

Two types of volcanic constructs and their contrasting behavior:

• shield volcanos: basaltic, low angle slopes and often very large, quieter eruptions, small summit calderas, example Hawaiian islands.
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  • Example above is of the small Belknap shield volcano that is part of the Cascade chain of volcanism. The foreground is relatively young basalt lava flow. Below is a small image of the top of the Mauna Loa shield volcano. Image source USGS website: http://pubs.usgs.gov/gip/volc/types.html
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• strato or composite volcanos: andesitic, high angle slopes, sometimes very large calderas, potential for very devestating eruptions, example Mt. Fuji.
  • The example below is of Mount Rainier with Tacoma in the foreground. Ancient lahars from Mount Ranier can be found beneath the outskirts of Tacoma.Image source: http://vulcan.wr.usgs.gov/Volcanoes/Rainier/images.html
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  • Comparison above of shield versus composite volcanos. Image source: http://vulcan.wr.usgs.gov/Glossary/VolcanoTypes/Graphics/graphic_shield_vs_composite_volcano.html
• what is determining these two different types of volcanic constructs?
• constructive and destructive phases of some composite volcanos.

What plate settings do different types of volcanism occur in?

Iceland - land of fire and ice, and lots of basalt:

• anomalous emergent portion of a seafloor spreading ridge, so basalt dominated. Map below shows the position of the active rift and related volcanoes (as red triangles). Imagefrom USGS website: http://pubs.usgs.gov/gip/dynamic/understanding.html
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  • Image from NASA Visible Earth of Iceland. Click on it for the larger image. Source: http://visibleearth.nasa.gov/view_rec.php?id=4702
• case history of Heimay eruption. Images below of houses destroyed by 1973 Heimay flow and air fall material from USGS web site: http://pubs.usgs.gov/gip/heimaey/
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  • USGS website on lava cooling operations at Heimay: http://pubs.usgs.gov/of/1997/of97-724/index.html
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• fire + ice = jokulhaups.
• hot springs and geothermal energy.

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  Figure of a geysir in Iceland, with a jet of steam just erupting through the overlying water and initiating an eruption. This feature erupted about every 5 minutes. Note the light colored cinter around that represents silica precipitating out of the hot waters. This activity is fed by magma and hot volcanic rocks at depth.

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Volcanos on the web. Fun, extensive web resource - many others.

Next lecture outline on volcanos.