CHAPTER 3: Volcanoes and the Rock Cycle
lesson 1:
Volcanic Eruptions and Structures
Assignment #1
Read pages 250-255 (Volcanic Eruptions) and write down the word(s) that complete
each statement.
1. _____________________ are areas on Earth’s surface where magma and
volcanic gases come out of the earth.
2. _____________________ eruptions are the most common type of eruption.
These involve the relatively calm flow of _____________.
3. During an explosive eruption, clouds of hot _____________, ______________,
and ___________ rapidly shoot out from a volcano.
4. Explosive eruptions cause magma to be blown into small particles that
__________ in the air.
5. The body of molten rock deep underground that feeds a volcano is called a
_____________ ________________. Circular openings through which this
molten rock escapes are called the ________________ of the volcano.
6. Magma that contains a high amount of ______________ and
________________is more likely to produce an explosive eruption. The
_______________ tends to produce high gas pressures within the magma and the
__________________ tends to make the magma stiff and slow flowing, which
can produce “clogs” in the volcanic vents (this causes high pressures to build
before an eruption occurs). (hint: same two answers, each used twice)
7. Magma erupts from a volcano as either ____________ or
_________________.
8. _______________________ forms when magma is blasted into the air and
hardens or as existing rock is shattered during an explosive eruption.
9. A fluid that has difficulty flowing is said to have a high ________________.
10. ___________________ ________________ forms when cooling magma
forms rock that is shattered into tiny slivers by the force of an explosive
eruption. This can remain in the air for weeks or even years and travel far
from the volcano.
11. The most dangerous hazard of an explosive eruption is a
___________________ ______________________, in which enormous
amounts of dust, ash, and gas is ejected from a volcano. Instead of rising, the
heavy (and very hot) cloud sinks and races down the side of the volcano at
speeds of over ____________ km/h (that’s about 120 miles per hour).
Assignment #2
Read chapter 9, pages 256-258 (Effects of Volcanic Eruptions).
1. During large-scale eruptions, large amounts of dust and ash are ejected into the
upper atmosphere. Ash and dust in the atmosphere causes some of the incoming
____________________ to be blocked, causing global __________________ to
drop.
2. The climate change caused by some volcanic eruptions can affect people by
causing _______________ shortages in parts of the world.
3-9. Matching:
Choices:
Shield volcano (S) Cinder Cone volcano (CC)
Composite Volcano (COMP)
3. These commonly occur in clusters on the sides of other volcanoes. _________
4. These are built of layers of lava released by repeated nonexplosive eruptions. ___
5. These are formed of mainly pyroclastic material from repeated moderately
explosive eruptions.
___________
6. These are sometimes called “stratovolcanoes” because they can grow to enormous
heights above sea level.
___________
7. These form broad mountains with gently sloping sides.
___________
8. These form from explosive eruptions of pyroclastic material followed by quieter
flows of lava. They have broad bases that get steeper toward the top. _________
9. These usually erode quickly because the pyroclastic material is not cemented
together.
___________
End Matching
10. Around the central vent of many volcanoes is a funnel-shaped pit called a
_________________. They form when magma remaining in the vent following an
eruption ______________ back underground.
11. In the case of shield volcanoes, the magma chambers are shallow. If the chamber
partially empties (as the result of a large eruption of decrease in magma supply
from the mantle), the entire top of the mountain may collapse downward,
producing a _______________________. These are similar to craters but many
times _____________________.
Assignment #3
Read pages 260-267 (Causes of Volcanic Eruptions)
1. Magma forms in many places along divergent boundaries due to a decrease in
________________ acting on the mantle rock. The magma comes from the mantle
and is low in silica. Eruptions here tend to be ___________________ in type.
2.
Magma forms over hot spots due to an increase in ___________________ of the
mantle rock. The magma comes from the mantle and is low in silica. Eruptions
here tend to be ___________________ in type.
3. Magma forms over subduction zones due the release of __________________
from the subducting plate. This lowers the _____________________
_____________________ of the surrounding crustal rock, causing it to melt.
4. The magma that feeds “subduction zone volcanoes” comes from the crust, and is
high in silica and water. This causes the eruptions to be ________________ in
type. About _______________ % of volcanoes on land are this type.
5. Most of the world’s subduction zone volcanoes occur along the rim of the
_________________ ocean. This area is known as the ____________________
__________ ______________.
6. About ___________ % of volcanoes on land form along divergent boundaries and
about ___________ % form over hot spots.
7. Volcanoes are classified into categories based on their activity.
___________________ volcanoes have not erupted in recent history and probably
will never erupt again. ______________________ volcanoes are currently
erupting or show signs of erupting in the near future. ___________________
volcanoes are not currently erupting, but are expected to erupt again.
8. Most active volcanoes produce small ____________________ as magma within
moves upward, causing rocks to shift. An increase in the _________________
and ___________________ of these can signal an upcoming eruption.
9. To monitor the activity of volcanoes, scientists study the volume and composition
of ________________ __________________. The ratio of
___________________________ to ___________________________ is an
important factor in predicting eruptions. An ___________________ in this ratio
may indicate a future eruption.
10. Often, before a volcano erupts, its shape starts to _________________. An
instrument called a _____________________ can measure changes in the slope of
the mountain.
11. ____________________ satellite images of a volcano are monitored to study the
_________________ near the surface of a volcano. If this increases, magma is
moving upward toward the surface.