Study Guide Chapter 7
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Magma is inside a volcano and lava when it comes out.
The Ring of Fire is a major volcanic belt formed by the many volcanoes that rim the Pacific Ocean.
Most volcanoes are found along diverging plate boundaries and converging plate boundaries.
A hot spot is an area where material deep within the mantle rises and melts through the crust above it.
An example of a hot spot volcano would be the Hawaiian Islands and Yellowstone National Park in wyoming
High viscosity fluids flow slower and low viscosity fluids flow faster
Silica content and temperature are the two factors that determine the viscosity of magma.
Silica- the less silica magma contains, lower its viscosity/ The more silica it contains, the higher the viscosity.
Temperature- the hotter magma is, the lower the viscosity/ The cooler magma is the higher the viscosity.
Pahoehoe – fast moving, low viscosity, smooth, wrinkly, rope like surface
AA- slow moving, high viscosity, rough chunks
Make sure you study this.
Dissolved gases (or trapped gases) provide the force that causes magma to erupt.
Quiet eruption- magma is low in silica, viscosity is low, flows easily
Explosive eruption- magma is high in silica, high viscosity, does not flow easily
Both Pahoehoe and Aa are produced in a quiet eruption.
Ash, cinders, bombs, and gases are the 4 things that can come from an explosive eruption.
A pyroclastic flow is an explosive eruption that hurls out a mixture of hot gases, ash, cinders, and bombs.
Some volcanic hazards, besides lava are fire, ash could bury everything, collapse roofs if wet, stop jet engines from
working, deadly gases, landslides, and avalanches, mudslides, as well cinders, and bombs
Active- is erupting or shows signs that it may erupt in the near future, dormant- not erupting now but may erupt
in the future, extinct- dead, unlikely to erupt again. (Make sure you know the difference between active and
dormant.)
The three types of volcanoes are shield, composite, and cinder cone- study diagrams of each in notes or page 219
Kinds of eruptions for the three types of volcanoes: Shield- quiet eruption, composite- quiet and explosive, cinder
cone- explosive
A lava plateau is a high level area where lava flows out of several long cracks; thin runny lava goes far before
cooling and solidifying. Lava flows on top of earlier lava and builds up a plateau.
A caldera is a huge hole left by a collapse of a volcano. A caldera forms when there has been an explosive eruption
and the vent and magma chamber are left empty. The volcano is hollow inside, so it collapses because there is
nothing to support the weight.
Some people may want to live near a volcano because of the fertile soil. Other reasons may be the geothermal
activity that can produce electricity, and also to study the volcano.
A volcanic neck forms when magma hardens in the pipe of a volcano. The softer rock around the pipe wears away,
exposing the hard rock.
Batholiths form when a large body of magma cools inside the crust.
Geothermal activity is the heating of underground water.
A hot spring forms when ground water is heated by a nearby body of magma or by hot rock deep underground. The
water rises to the surface and collects in a natural pool.
A geyser forms when rising water and steam become trapped underground in a narrow crack. Pressure builds until
Make sure you are familiar with your key terms and the
the mixture suddenly sprays above the surface.
information on your red foldable, be able to identify the 3 type of
Old Faithful
Geothermal energy can be used as a form of electricity volcanoes from pictures, make sure you can identify the parts of a
volcano (definitions or pictures).