Study Guide Chapter 5
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Exam 2 Study Guide: Part 1
Chapter 5: Volcanoes
1.
What are the three main ways magma is formed? (1 pt)
a.
Decompression Melting occurs when rock moves from high to lower pressure,
typically as it rises through the Earth's crust. As the pressure decreases, the rock melts
and forms magma.
b.
Addition of Heat: When heat is added to the Earth's crust, it can raise the
temperature of the rock until it melts and forms magma. This can happen through
processes like mantle plumes or the intrusion of hot magma into cooler rock.
c.
Addition of Volatiles (Water and Gases): The presence of water and other volatile
substances can lower the melting point of rock, causing it to melt and form magma. This
often occurs at subduction zones where oceanic plates sink beneath continental plates.
2.
What is the relationship between plate tectonics and the location of volcanoes? Where on
Earth are the majority of active volcanoes located? (1 pt)
Volcanoes are closely related to plate tectonics. Most volcanoes are found at plate boundaries.
Most active volcanoes are located along the Pacific Ring of Fire, which encircles the Pacific
Ocean. This is because the Ring of Fire is a region where several tectonic plates converge,
leading to subduction zones, rift zones, and transform boundaries where volcanic activity is
common.
3.
Describe the major types of volcanoes and their composition (rock/magma types). Which
magma type has the most silica? The least silica? (1 pt)
a.
Shield Volcanoes: These volcanoes have broad, gently sloping sides and are
primarily composed of basaltic magma, which has low silica content.
b.
Stratovolcanoes (Composite Volcanoes): Stratovolcanoes have steep-sided
profiles and are composed of alternating layers of lava flows, ash, and volcanic rocks.
They often erupt andesitic or dacitic magma with intermediate to high silica content.
c.
Cinder Cone Volcanoes: Cinder cones are small, steep-sided volcanoes made up
of volcanic fragments like ash and cinders. They typically erupt basaltic magma.
4.
Describe the primary and secondary effects of volcanic eruptions. (1 pt)
Primary effects include lava flows, ash clouds, pyroclastic flows, and volcanic gases. Secondary
effects include mudflows, tsunamis (if the volcano is near the ocean), and long-term climate
impacts due to ash in the atmosphere.
5.
Describe the natural service functions provided by volcanoes. (1 pt)
Volcanoes provide essential services like fertile soil for agriculture, geothermal energy resources,
and mineral deposits. They also play a role in shaping landscapes and supporting unique
ecosystems.
6.
What methods are used to control lava flows? (1 pt)
Lava flows are challenging to control directly. Methods often involve diverting or cooling the
lava. Barriers, like walls or trenches, can be constructed to try to redirect the flow away from
populated areas. Additionally, water can be used to cool and solidify the lava to slow its advance.
7.
What methods are used to forecast volcanic hazards? (1 pt)
Scientists use various methods, including monitoring ground deformation, gas emissions, seismic
activity, and thermal imaging to forecast volcanic eruptions. They also rely on historical data and
trends to make predictions.
8.
How can volcanic eruptions affect global climate? (1 pt)
Large volcanic eruptions can inject significant amounts of ash and gases into the atmosphere,
which can lead to short-term cooling by blocking sunlight. This phenomenon is known as
volcanic winter.
9.
What part of the United States has the greatest volcanic hazards, and why? (1 pt)
The Pacific Northwest, including areas in Washington, Oregon, and northern California, has
some of the greatest volcanic hazards in the United States. This is due to the presence of the
Cascade Range, which includes several active volcanoes like Mount St. Helens and Mount
Rainier.
10.
What are some perceptions of volcanic hazards? (1 pt)
Perceptions of volcanic hazards can vary. Some people living near volcanoes may be aware of
the risks and preparedness measures. Others may underestimate the dangers or view volcanoes as
tourist attractions. Public education and awareness are crucial for managing volcanic hazards
effectively.
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