Ch 7 Study Guide
Concepts to Know
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Know the difference between the three types of volcanoes
Know how the Hawaiian islands are formed
Know the types of earths materials that erupt from volcanoes
Identify and explain the factors that affect the force of a volcanic eruption
o The force of a volcanic eruption depends on its viscosity. The viscosity is determined by
its temperature and its silica content. The hotter the magma is, the thinner it is and the
quieter its eruption. The more silica the magma contains, the thicker it is an the more
explosive its eruption
The most recent earthquake in Yellowstone National Park changed the volcanic activity there.
Some geysers now erupt at different intervals than they did before. A few geysers have
stopped erupting, and some new geysers have formed. Explain what might have happened
during the earthquake to change the geyser activity
o Earthquakes are produced by movement of Earth’s crust along faults. During the most
recent earthquake in Yellowstone, underground movements may have changed the
channels through which heated water reached geysers on the surface. Some channels
may have been blocked, cutting off geysers. Some new channels may have opened,
creating new geysers. Other channels may have widened or narrowed, changing their
geysers eruption intervals
Explain why ash, cinders, and bombs are produced only in explosive eruptions, not in quiet
eruptions
o In order for ashes, cinders, and bombs to form lava must be ejected forcefully from a
volcano, so it is broken into fragments that cool and harden quickly to form pieces of
different sizes
What is geothermal energy? How is it used?
o Geothermal energy is energy derived from water that has been hearted by magma
underground. Hot water is piped to buildings as a heat source and steam is piped into
turbines to generate electricity
A volcano that is erupting or has shown signs that it may erupt in the future is called active
Layers of thin, runny lava that flow over a wide area before they cool and harden can build up a
lava plate
Volcanic soils are fertile because they contain potassium and phosphorus
High in silica is not a physical property of magma from an explosive eruption
Inside a volcano, magma collects in pocket called a magma chamber
An area where magma melts through the crust in the middle of a plate is called a hot spot
The molten mixture of rock-forming substances, gases, and water deep in Earth’s mantle is
called magma
The Ring of Fire is a belt of volcanoes around the rim of the Pacific Ocean
The more silica that magma contains, the thicker the magma is
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A pyroclastic flow happens when an explosive eruption hurls ash, cinders, bombs, and gases out
of a volcano
A shield volcano is a wide, gently sloping mountain made of hardened layers of low-silica lava
A volcanic neck forms when magma hardens in a volcano’s pipe and is later exposed
A substance that cannot be broken down into other substances is an element
A substances ability to burn is an example of a chemical property
A volcano is a weak spot in the crust where magma comes through
Liquid magma flows upward through the crust because it is less dense than the solid material
around it
Pahoehoe and aa are produced during quiet eruptions
A geyser is hot water and steam that erupts from the ground
When the top of a volcanic mountain collapses, a caldera forms
A batholiths is a mass of rock that formed when a large body of magma cooled inside Earth’s
crust