Download Blizzard Bag 1

Name
Date
Class
Blizzard Bag #1
Volcanic Mountains, Bicycles, and Frankenstein
Volcanic mountains are very different
from other mountains because they are not
formed by folding and crumpling or by
uplift and erosion. A volcanic mountain is
built by the accumulation of materials that
have erupted from the volcano. Molten
rock pours from the vent and cools on the
slope. Lava may shoot into the air, fall back
on the cone, and move downslope as
ashfall. In this way, the volcano forms a
mountain with slopes.
Where are they?
The Hawaiian Islands are the tops of
volcanic mountains that are mostly
submerged in the sea. Other volcanic
mountains form in what are called island
arcs. These arcs form when two plates
converge and form a subduction zone.
Magma rises from the subduction zone and
builds submarine volcanoes that, over time,
grow above sea level. This process can
result in an arc-shaped island chain. The
Aleutian chain and the Indonesian chain
are examples of island arcs.
Fire Mountain
The 17,500 islands of Indonesia are an
island arc located in a zone of especially
violent geophysical activity at the juncture
of colliding plates. Nowhere on Earth do so
many people live so close to so many active
volcanoes—129 volcanoes have been
counted in this area.
Mount Merapi, or Fire Mountain, in
Indonesia is one of the world’s most active
and dangerous volcanoes. Despite the
constant threat of volcanic activity,
however, farmers build villages on the
slopes of the mountain where the land is
so fertile from volcanic ash that they can
harvest three crops of rice in one season.
Far-Reaching Effects
If you don’t live near any volcanic
mountains, you might think that they
have no effect on you. Think again. In
1815, Mount Tambora in Indonesia
exploded and continued erupting for three
months. Volcanic dust in the atmosphere
blocked out the Sun, the decreased warmth
changed wind and current movements, and
cold arctic air moved south. Summer
temperatures were eight degrees colder
than normal. In the United States, New
England farms were wiped out, and
thousands of people immigrated westward.
Applying Critical-Thinking Skills
Directions: Respond to each statement using complete sentences.
1. Explain how volcanic mountains are different from other kinds of mountains. (Answer using no less
than two complete sentences.)
2. Using the map on the next page, explain which of the following plates are involved in the
formation of the Aleutian Island arc and the Indonesian Island arc: Antarctic, Pacific, Eurasian, North
American, Indo-Australian, African. Identify the subducting plate in each convergence. (Answer
completely, using no less than 3 sentences.)
Earth Dynamics
59