Transcript Ch. 7 - Volcanoes - Trimble County Schools

18.2 - Eruptions
Making Magma
 Activity
depends on ____________ of magma
 Lava can be thin & __________ or ___________
& lumpy
Magma
Temperature
 Most rocks melt between _______-1200 °C
 In Crust & Upper _____________
Pressure
 Increase with ________ because of _________ of
rocks
 High pressure increases ___________ temperature
Composition of Magma
Amount of Gas & Silica
 Increase gas dissolved = ______________
explosiveness
 _____________+ gases = carbon dioxide, water
vapor, sulfur oxide, sulfuric acid
 Water vapor determines _________ magma forms
 Water vapor ______________ melting temperature
Composition
________________ = Resistance to flow
 Temperature & silica content affect ____________
 High viscosity = __________ magma
 High silica = _____________ & sticky
 Traps
 Low
gases, produces explosive eruptions
silica = __________ & runny
 Flow
easily, produce quiet, non-explosive eruptions
Types of Magma - Basaltic
 Less
then __________ silica content
 __________-viscosity magma
 Gas ____________ escapes
 ______________ eruptions
 Ex: Kilauea & Mauna Loa
http://media-2.web.britannica.com/eb-media/31/20231-004-008EFA7E.jpg
Types of Magma - Andesitic
 50-_________
silica content
 Oceanic-continental ___________ zones
 _______________ viscosity
 _______________ explosiveness
 Send __________ volumes of ash & debris
 Ex: Colima Volcano in Mexico
http://images.livescience.com/images/050531_colima_volcano_04.jpg
Types of Magma - Rhyolitic
 More
than _________ silica content
 Magma ___________ with water and silica
 _____________ viscosity
 ____________ volumes of gas trapped
 ___________ explosive
Explosive Eruptions
 If
lava is too ____________ to flow, pressure
builds up until an __________________
 _____________ = ash and pieces of solidified lava
or pieces of crust
 Classified
by _________
 ________ = smallest tephra, diameter is less then 2 mm
 Blocks = largest tephra
Ash
 Can
________ into atmosphere
 _________ sulfuric acid
droplets remain in stratosphere
and ____________ sun’s rays
and ______________ global
temperature
http://geology.com/articles/volcanic-ash/volcanic-ash-column.jpg
Pyroclastic Flows
 Tephra
+ gases
 VERY ___________
http://vulcan.wr.usgs.gov/Imgs/Jpg/MSH/Images/MSH80_pyroclastic_flow_from_st_helens_crater_08-07-80.jpg
In-Class Assignment
 18.2
Study Guide WKT