cinder cone, San Bernardino Valley,
Cochise County, Arizona
Vocabulary
aa lava flow
-is a lava flow with a very blocky, sharp
surface.
Aa is a word used by bare-footed Hawaiians to describe this sharp,
skin-ripping type of
basaltic lava.
-consist of a prominent curved chain of
volcanic islands extending from Alaska westward.
Structurally, these islands
are an island arc adjacent to a subduction zone.
-is an igneous intrusion (pluton) that has
many cracks radiating from the main magma
body
and filled with magma from the
intrusion; so named because of a fanciful
comparison to a cactus.
caldera
-is a large collapse depression on top of a
volcano.
-is a gas denser than air; each molecule
consists of one carbon atom and two oxygen
atoms.
It is used to produce the
bubbles in soda pop.
carbon monoxide
-is a deadly gas produced by incomplete
combustion of fossil fuels.
Each molecule of this compound consists of one
carbon atom and one oxygen atom.
Cascades
-consist of a chain of andesitic volcanoes
extending from California to British
Columbia. Located within the Cascades are
Mt. Rainier, Mt. St. Helens, Lassen Peak,
Crater Lake, and others.
cations
-are atoms or groups of atoms with excess positive electrical charge, such as:
Ca+2, Na+1, K+1,
Al+3, Mg+2, Fe+2, Fe+3, etc.
chill zone
-is the outer part of a magma body that
cools quicker because it is in contact with
the cooler
country
rock;
consequently grain sizes in the chill zone are smaller than
for the rest of the
magma
body. -chill
zone-Opal's Pals
cinders
-are small pyroclastic fragments of
vesicular basalt ejected from a volcano;
commonly about one
quarter inch to one
half inch in diameter.
-represent huge outpourings of fluid
basaltic lava which inundated a large
area of the Pacific
Northwest
of the
United States.
columnar jointing
-Upon cooling, igneous bodies shrink and
crack in a hexagonal pattern on
a horizontal plane;
these cracks
continue to
migrate downwards through
the cooling igneous body to create a
structure built
of six-sided columns.
crystal settling
-occurs within a magma chamber when crystals of a mineral form that are
denser
than the magma.
The denser crystals tend to sink to the bottom
of the magma chamber, removing
certain elements
and thereby changing
the composition of the magma. -crystal
settling-Opal's Pals
-is an intrusion, such as a dike, that cuts
across the grain or layering of
the pre-existing rock
(country rock). -dike
near Yuma, Arizona
dissolved gases
-Within a can or bottle of soda there a
significant amount of gas dissolved
within the fluid; without
it the soda
would
be flat. Similarly, there are many
varieties of gasses dissolved in magma which
are released when lava
erupts:
steam, carbon dioxide, sulfur dioxide,
hydrochloric acid, chlorine,
hydrofluoric acid, etc.
Flagstaff volcanics
-are located north of Flagstaff, Arizona;
the area has many cinder cones and
lava flows.
-Under the influence of gravity crystals
that form as as a magma cools either
settle to the bottom of
the magma
chamber
(dense compounds) or rise to the
roof of the magma chamber (low density
compounds).
-gravitational magmatic segregation-Opal's Pals
-is a term applied to a small region in
which a prolific amount of magma is
being generated over
a long interval
of
geologic time; since crustal plates
move over these buried sources of magma,
the
result is a trail of volcanoes
and/or intrusions on the crustal plate. -trail of the Yellowstone hot spot in Wyoming -trail of hotspot in Mexico**
hydrochloric acid
-is an acid with the formula, HCl. It is
found in increased but minor quantities
in your stomach
when you take
an algebra
or calculus test. It is also one of
the volcanic gases.
hydrofluoric acid
-is an extremely powerful acid with the
formula, HF. Hydrofluoric acid is capable
of dissolving
glass, quartz,
and the
corneas of your eyes.
ignimbrite eruption
-is also known as a glowing cloud eruption. It consists of a fast moving,
dense
cloud of red-hot
pyroclastics,
destroying everything in its path.
-ignimbrite lecture
intrusion
-is an igneous pluton, where magma has
intruded country rock.
-is a large, mushroom-shaped concordant
intrusion. The most famous
laccoliths are found in the
Henry
Mountains of
southern Utah.
-laccolith-Opal's Pals
lahar
-a mud flow coming off of a volcano.
Lassen Peak, California
-is an andesitic cone, part of the Cascades
volcanics.
-is a hill-like structure made of viscous
magma, formed on top of a
composite volcano often
following a violent
explosive
event.
The present summit of Mt. St. Helens has one of these
structures
starting
to fill the gap where
the top of the volcano was blown off.
-is a volcanic caldera fills with yellow-hot
fluid lava; the surface of a lava
rapidly cools to a dark,
non-luminescent
material, but beneath the thin
crust the lava is still molten.
-is a cylindrical cavity that forms as
basaltic lava drains out beneath a
hardened surface crust. Some lava tubes are
caves as large as a subway
tunnel.
-occurs when magma from two or more
different sources come together
and mix underground.
magmatic differentiation
-is the process whereby the composition of a
magma changes as it cools
and newly crystallized
minerals
separate from the
magma.
magmatic stoping
-occurs when a magma body moves
upwards by cracking the ceiling rocks
by pressure and
allowing
fragments of the country
rock to fall into the
magma chamber. Stoping is a mining term
for mining
upwards. -magmatic
stoping-Opal's Pals
mantle plume
-hot, low density molten (or semi-molten)
material rises from the mantle
and comes up underneath
the crust.
-is a famous cinder cone that formed in a
cornfield in Mexico.
parasitic cone
-is a small volcanic cone formed on top of a
larger volcano.
partial melting
-occurs as a subducted slab of crust moves
down a subduction zone.
Minerals within the slab with the lowest melting
temperatures melt first. -partial melting-Opal's Pals
pyroclastics
-are the hot fiery fragments tossed out of a volcano.
resurgent caldera
-is a silicic form of volcanism in which a
collapse crater is formed after
the explosive eruption of a
magma chamber that
has uplifted the surface
of the Earth. Magma production after the main
eruption
does not cease;
at a later time new magma domes the floor of the crater; in
other words
the surface
surges upwards again to provide the "re" in resurgent. -resurgent caldera and welded tuff lecture
-occurs along the crest of oceanic ridges
where the oceanic crust is being
pulled apart and lava is
filling the fissures,
thereby creating new seafloor.
shield volcano
-is a large basaltic volcano that is very
wide but has a low profile. This type
of volcano is so
named
because it
resembles a Roman shield laid flat on the
ground. The most famous volcanoes
of
this type
located on Earth are the
Hawaiian and Galapagos islands. -Haleakala, Maui, Hawaii -Lanai, Hawaii -shield
volcano-Opal's Pals
Shiprock, New Mexico
-is an outstanding weathered volcanic neck
on the northeastern portion of
New Mexico.
All that remains is a shark peak
with three radiating dikes.
-Shiprock
sill
-is a concordant intrusion of magma between layers of country rock. -sill-Opal's
Pals
-is a composite volcano made of alternating
layers of ash and lava; intermediate
in composition.
Many of the most famous
and prominent volcanoes in the
world are of this type: Mt. Fuji,
Mt. Rainier,
Mt. St. Helens, Mt. Shasta,
Mt. Kilimanjaro, Lassen Peak, etc.
-In a subduction zone, a slab of oceanic
crust with sediments is subducted
down into the hot mantle
where low temperature
minerals in the slab
start to melt. The newly formed magma rises to the
surface
adjacent to
the trench to produce volcanoes.
-subduction zone volcanics-Opal's Pals
sulfur dioxide
-is a poisonous gas given off by volcanoes.
Upon exposure to oxygen in
the air plus sunlight, sulfur
dioxide
turns into
sulfur trioxide that then
combines with moisture to form sulfuric acid and then
goes on to become
acid rain. -sulfur
dioxide-Opal's Pals
sulfuric acid
-is a powerful acid whose formula is
hydrogen sulfate.
Sunset crater, northern Arizona
-is a cinder cone north of Flagstaff,
Arizona. This small volcano is reported
to be the most recent
volcanic
eruption
in Arizona.
-Sunset Crater
tuff
-is an igneous rock consisting of compacted
volcanic fragments smaller
than one eighth of an inch. -tuff
Turkey Creek caldera, Cochise County,
Arizona
-is a large, eroded resurgent caldera in the
Chiricahua Mountains of
southeastern Arizona;
radiometrically
dated at 26
million years old.
-is a new, hardly weathered resurgent
caldera, complete with resurgent dome
and moat volcanics
northwest of
Albuquerque, New Mexico. -Valles Caldera
geologic maps
Vesuvius
-is an active volcano in Italy that is
responsible for destroying Pompeii and
Herculaneum.
viscosity
-is the measure of how resistant a fluid
material is to flowing.
For example, corn syrup is more viscous than water.
-viscosity-Opal's Pals
volcanic ash
-consists of very fine volcanic materials,
ranging from dust to particles less
than one eighth of an
inch.
volcanic bomb
-is a blob of lava ejected out of an active
volcano. As the material sails
through the air, the outer
surface of the
projectile cools and solidifies
before it hits the ground. Commonly, these
molten
blobs are spinning
as they
are ejected from the volcano and may develop
aerodynamic or
twisted
shapes.
-is a steep-sided, hill-like mass of viscous
lava extruded by a volcano; after
the explosive eruption
of Mt. St. Helens,
one
of these features slowly formed
in the newly created gap at the top of the
volcano; also called a lava dome.
-are the most common gases emitted by
volcanoes: steam, carbon dioxide,
sulfur dioxide,
hydrochloric acid,
chlorine,
hydrofluoric acid, fluorine, carbon
monoxide, and methane.
volcanic neck
-After a volcano has undergone intense
weathering, all that often remains
is the lava that cooled
and hardened
in the
conduit that supplied lava to
the volcano. -Shiprock, New Mexico
-Shiprock, New Mexico-2
-is hot, silicic ash from a violent volcanic
eruption melts back together
on the ground due to its high
temperature
and the
weight of the volcanic
ash (tuff) above it.
Weller's spaghetti theory of magma
-explains how the constituents of magma (silica, cations,
and dissolved gases)
affect the viscosity of a magma. -Weller's
spaghetti theory of magma-Opal's Pals *
xenoliths
-are fragments of country rock that have fallen into a magma chamber and
are
slowly being baked,
then melted,
and finally added to the magma. -xenolith
-xenoliths-Opal's Pals
Chapter 4- Volcanoes and Plutons