Volcano Vocabulary
VOLCANISM
VENT
CRATER
CALDERA
QUIET ERUPTION
EXPLOSIVE ERUPTION
PYROCLASTIC DEBRIS
CINDER CONE
SHIELD VOLCANO
COMPOSITE VOLCANO
STRATO VOLCANO
ACTIVE
DORMANT
EXTINCT
INTRUSION
DIKE
SILL
LACCOLITH
PLUTON
BATHOLITH
STOCK
ROCK CYCLE
REMELTED
BURIED
REMELTED
BURIED
HEAT
PRESSURE
ERODED
TRANSPORTED
DEPOSITED
ERODED, TRANSPORTED
DEPOSITED
HEAT
PRESSURE
I.
Heat within the Earth
A. For every ______________ we go beneath the surface the
temperature increases _______ degrees Celsius.
B. Sources of heat:
1. ____________________________ decay- like a thermonuclear
reactor is partly responsible for heat within the Earth. Atoms are
splitting apart or decaying.
2. Original ____________________- Crust has insulated the heat
trapped within since the Earth's formation about 5
________________ years ago.
3. ______________________- Tremendous heat created from the
convection currents within the _________________________.
II.
Magma (molten rock ______________________ the surface that is
mostly silica)
A. Formation
1. Molten rock within the Earth is called ____________________.
Molten rock extruded onto the surface is called
________________. Magma forms at a depth of about 40 to 60
kilometers. Magma _______________________ have a
temperature of 650 to 1500 degrees Celsius- or about 1,200 to
3,000 degrees Fahrenheit.
B. Types/ Chemical Composition of Magma
1. __________________- Also known as Pahoehoe, Mafic and
Oceanic.
Contains less percentages of silica (SiO2) and more Magnesium
oxide (MgO). It has a very thin, runny texture or
_________________ viscosity.
Temperature of Mafic lava ranges between 1000 and 1500 degrees
Celsius. High relative _______________________.
2. ____________________- Also known as aa, Felsic and
Continental. Contains more silica (SiO2) and Aluminum oxide
(Al2O3).
It has a __________________ and pasty texture or high viscosity.
Temperature of Felsic lava is about 650 to 950 degrees Celsius.
________________________ relative density.
Magma Type:
FELSIC
INTERMEDIATE
MAFIC
75% SiO<--------------<-----------------<-------------------<--------------------45% SiO2
increasing percentage of silica
<--------------<----------------<-------------------<--------------------increasing Na2O & K2O
---------------->---------------->-------------------->-------------------->
increasing CaO, FeO, & MgO
Common Rock:
RHYOLITE
GRANITE
ANDESITE
BASALT
GABBRO
III. Anatomy of a Volcano
A. Common Features
1.
_______________________ Chamber- as magma rises to the
surface it forms a large pocket beneath the surface that holds
the magma.
AKA: ______________________, Batholith, Stock
2.
______________________- is a narrow crack in the crust or
bedrock through which magma flows.
3.
_____________________- central opening that allows the
magma to flow to surface. Where magma leaves the pipe.
4.
______________________ - the basin or bowl-like depression
over the vent at the ______________________ of the cone.
IV. Kinds of Eruptions
A. ________________________ Eruption
1. Typical of the Basaltic/Mafic/Oceanic _______________ flow.
A "fissure flow" describes lava running out onto the surface in
wide, thin sheets. Often these sheets form a ropy surface called
__________________________________- which means "satin-like".
These flows can lead to a topography called a _________________
Plateau.
Mauna Loa (Hawaii) is a good example of a series of quietly
erupting lava.
B. ______________________________ Eruption
1. Typical of the _______________________ /Felsic/Continental
lava flow.
When lava of this type erupts, a great deal of gas and ash erupt
with it. The appearance of this kind of lava is sharp and jagged
which led to its name- _______________ . The particulate matter
that explodes from the volcano is called Pyroclastic Debris.
a. Pyroclastic Debris (AKA: ________________ ) is
categorized by size:
~Smallest is called Tuff or ___________________
~Sand-sized particles are called _______________
~Pebble-sized particles are called ______________
~Cobble to truck-sized called Volcanic ________________
V. Types of Volcanoes
A. Classification
Volcanic classification is determined by composition & _____________.
The ____________________________________ determines chemistry of
magma/lava and consequently the type of eruption as well. The
material ejected from the volcano and deposited around the vent
produces the _____________________.
B. Types
1. ___________________________ - is a small, steep-sided volcano
made mostly of cinders & tuff (tephra), often with lava flows
intermixed.
The height is usually less than ____________ feet (200 meters).
The Cinder Cone tends to erode quickly and may bleed from the
bottom or sides- called a "________________ eruption". These
volcanoes ______________________often cause damage in that
they are small, intermittent explosions of Felsic lava.
Examples are _____________________________ (Crater Lake) and
Paricutin (1943, Mexico).
2. ___________________ Volcano- is usually wider than it is tall,
much like a shield. It is almost entirely made of mafic lava
(____________________________ ).
The Shield has a 2 to 10 degree slope and most often found near
________________________ or on oceanic crust. The lava flow
itself can cause significant damage though its eruptions are
tectonically quiet.
An example is Mauna Loa (Hawaii)
a. ______________________ Volcano- is similar in structure
and composition to Shield Volcanoes. In this type of
structure, huge quantities of lava exude onto the surface
from fissures in the crust. These volcanoes are very
difficult to identify yet are very common. Sheet
Volcanoes are the largest volcanoes in area, often covering
thousands of square kilometers.
An example is the Columbia Plateau (Washington &
Oregon).
3. Composite or __________________ Volcano- is a large, steepsided volcano made of alternating layers of lava flow and
pyroclastic debris. Its structure and behavior is highly complex.
Strato Volcanoes are considered to be extremely _______________
due to their inconsistent behavior. These volcanoes are extremely
explosive at times, while at other times the eruptions are quiet.
The nature of the eruption is determined by the ________________
location.
_______________________ of Composite Volcanoes are Mount St.
Helens (Washington), Mount Vesuvius (Mediterranean), and
Mount Pinatubu (Philippines) which exploded in June of 1991.
a. The ___________________________________ , or nuees
ardentes, is the main killer in ___________________________
eruptions. The superheated gas rushes down the cone in
excess of ___________________ miles per hour and often
exceeds temperatures of 800 degrees Celsius or 1,500 degrees
Farenheit. On May 8, 1902 Mont Pele’e erupted on the
Caribbean island of Martinique. A nuees ardentes blew
down the slope at over 700 degrees Celsius killing
__________________ people in the city of St. Pierre within
only two minutes. Only __________________ people are
known to have survived.
b. __________________________ - a volcanic depression
much larger than the original crater. It is either an
exploded volcano or a _______________________ volcano.
Examples are Krakatoa (Indonesia) Crater Lake (Oregon),
and Mount St. Helens after 1980 (Washington).
VI. ___________________________________ of Volcanoes
1. ____________________ Volcano- is a volcano that is erupting now,
has erupted in the recent past, or shows signs of erupting in the near
future.
2. ________________________ Volcano- is a volcano that has not
erupted recently, but
has during recorded history. It is expected to
erupt again in the future.
3. _____________________________ Volcano- is one that has not
erupted in recorded history. It is unlikely to erupt again.
VII. Volcanism Underground
A. ____________________________________ - are flows of magma that
cool and harden before they reach the surface. Intrusive igneous
rocks have a large grain, or crystal, size.
The _____________ the intrusion, the _______________ the grain size
1. Volcanic _________________ - is an intrusive structure
composed of cooled magma trapped in the throat or vent of a
volcano.
2. ___________________________ - is a tabular, typically
_____________________________ intrusion (discordant).
Dikes formed at _____________________ depths can have
___________________________ grained texture, while those at
greater depths may have a coarse grained texture. Often dikes
will be ___________________ resistant to erosion and leave a walllike protrusion on the surface. An example is Ship Rock (New
Mexico). There also dikes in Wisconsin.
3. ___________________ - is a relatively horizontal structure that
is parallel (cordant) to the layers of country rock. Magma
squeezes ___________________________ sedimentary rock and
solidifies into a sill. Like dikes, the grain texture of a sill is
dependant upon ___________________ .
4. __________________________ - is a close relative of the sill
which often leaves a bulge at the surface. It has a slight dome or
______________________________ shape, with the middle of the
structure being thicker than the sides. These can form smaller
dome mountains.
5. ________________________ - is an igneous body that has
cooled and crystallized at great depths. Plutons have irregular
shapes and often cause ______________________ of bedrock at the
surface.
a. _____________________ - is a small discordant (nearly
vertical) pluton with an outcrop area of _____________ than
100 square kilometers.
b. ____________________________ - is a large discordant
pluton with an outcrop area of _______________ than 100
square kilometers. Most batholiths are felsic in composition,
being mostly granite.
Written and compiled by
Peter J. Watts
Riverside Middle School
131 Hall Street
Watertown, WI 53094
414-262-1480
wattsp@watertown.k12.wi.us
http://rms.watertown.k12.wi.us/RMS_Staff/wattsp/wattsp.htm