Volcanic Activity
How Magma Reaches the Surface
Magma rises because magma is less
__________ than the surrounding
_________ material.
 It will rise until it reaches the
___________ or becomes trapped
beneath _________ of _________.

A Volcano Erupts
A volcano erupts when an opening
develops in _________ _________ on the
surface.
 During a volcanic eruption, the _________
dissolved in __________ rush out,
carrying the magma with them.
Inside a Volcano:
 __________ ___________ – The pocket
beneath a volcano where magma collects

The magma moves through the _______,
a long tube in the ground that connects
the magma chamber to Earth’s surface.
 __________ - an opening in the volcano
where gases and molten rock leave.
 __________ ________ – The area
covered by lava as it pours out of a vent.
 Crater – A _________-__________ area
that may form at the top of a volcano
around the volcano’s central _________.

Characteristics of Magma
__________ content, how __________ or
_________ the magma is, temperature and silica
contents are important factors as to the
__________ of a volcanic eruptions.
 The amount of ___________ in magma helps to
determine how easily the magma flows. Silica is
formed from the elements ___________ and
___________ and is abundant in the crust and
___________. The __________ silica content in
magma the thicker the magma.

Types of Volcanic Eruptions
Silica content determines whether the volcanic
eruption is ___________ or ___________.
Quiet Eruption:
 A volcano erupts quietly if its magma flows
easily.
 Quiet eruptions produce two types of lava:
________________ – fast-moving, hot lava
_____ – cooler, slower moving lava

Explosive Eruptions:
 If magma is __________ and __________, a
volcano will erupt explosively.
 The explosion will break the lava into
___________ that quickly cool and harden into
pieces of different size called ___________.
 Smallest pieces are called _________ (fine,
rocky particles as small as a grain of sand),
___________ are pebble-sized particles and
___________ are larger pieces that range in size
from a baseball to a car.
Stages of a Volcano
____________ – a volcano that is
erupting or has shown signs that it may
erupt.
 ____________ – sleeping and may
become active in the future.
 ____________ – a volcano that is unlikely
to erupt again.

Other Types of Volcanic Activity
Hot Spring – forms when
______________ heated by a nearby
body of magma rises to the surface and
collects in a natural _________.
 Geyser – a fountain of ___________ and
__________ that erupts form the ground.
 _____________ ____________ – water
heated by magma that provides a clean,
reliable energy source.

Monitoring Volcanoes

Geologists have been somewhat
successful in predicting eruptions. They
use the same devices that are used to
monitor earthquakes (______________,
__________-___________ devices, etc.).
Geologist will also monitor the small
____________ that normally accompany a
volcano.
Volcano Hazards
Although quiet eruptions and explosive
eruptions involve different volcano
hazards, both types of eruptions can
cause damage far from the crater’s rim.
 Volcanic ash can bury entire towns,
damage ___________, and car
_____________. Eruptions can also cause
___________ and _______________.
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