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.
-aa lava flow near Flagstaff, Arizona
-aa lava flow in Craters of the Moon
National Park, Idaho
-Aa lava-Opal's
Pals
Aleutian Islands
-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.
-map of Alaska
Aleutian islands
anions
-are atoms or groups of atoms with excess negative electrical charge, such as:
Cl-1, SO4-2, CO3-2, S-2, etc
assimilation
-is the process by which magma melts
surrounding rocks (country rock) and adds these
new elements to its composition.
-assimilation-Opal's Pals
basaltic volcanism
a
quick guide to basaltic volcanism (a photo tour)
-basaltic volcanism, Baja California, Mexico
batholith
-is a very large igneous intrusion.
cactolith
-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.
-Halemaumau in Hawaii-overview
-Halemaumau in Hawaii-crater wall
carbon dioxide
-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.
-Lassen
Peak, California
-Crater
Lake, Oregon
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.
-cinders near Flagstaff. Arizona-1
-cinders near Flagstaff. Arizona-2
-cinders, Haleakala, Maui, Hawaii
cinder cone
-is a small volcano made of loose cinders at
the angle of repose (about a 35
degree angle slope).
-cinder cone near Flagstaff, Arizona
-cinder cone in Craters of the Moon National
Park, Idaho
-aerial photograph of cinder cones
-cinder cone in Haleakala crater, Maui, Hawaii
-cinder
cone-Opal's Pals
Columbia River basalts
-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.
-Devils Post Pile, California-vertical columns
composite volcano
-is a volcano made out of alternating layers
of ash and lava flows; also known
as a strato-volcano.
-composite volcanoes of the Cascade Mountains, Oregon**
-Lassen Peak, California
-composite
volcano-Opal's Pals
concordant intrusion
-is an intrusion of magma, such as a sill,
that goes between the layers of the
rock that it is intruding.
-concordant intrusion-Opal's Pals
contact metamorphism
-is a form of metamorphism where rocks are
baked by the heat from an
igneous intrusion.
-contact
metamorphism-Opal's Pals
country rock
is the pre-existing rock that into which a
magmatic intrusion invades.
-contact
between intrusion and country rock
-country
rock-Opal's Pals
crater
-is the large depression on top of a volcano.
-Halemaumau in Hawaii-overview
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
Devils Postpile, California
-Devils Postpile-vertical columns-1
-Devils Postpile-vertical columns-2
Devils Tower. Wyoming
-is an igneous intrusion in northwestern
Wyoming that cooled and formed
prominent columnar
jointing
before being exposed
by erosion.
dike
-is a discordant igneous intrusion that cuts
across the layering of the
country rock; the structure is
often
just igneous
material filling a crack.
-dike in the Santa Catalinas near Tucson,
Arizona
-dikes exposed by weathering
-aplite dike in decomposed granite, Huachuca
Mountains, Arizona
-radial dikes of Shiprock, New Mexico**
-Shiprock, New Mexico-dike A
-Shiprock, New Mexico-dike B
-granite dike in gneiss
-dike
near Yuma, Arizona
discordant intrusion
-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.
-cinder cones near Flagstaff, Arizona
-S.P. crater and lava flow-aerial view
flank eruption
-is an eruption from the side of a volcano
flood basalt
-is a form of basaltic eruption in which
huge flows of very fluid lava issue from
fissures.
-Idaho-Craters of the Moon
-flood
basalt-Opal's Pals
fumarole
-is the location where volcanic gasses emerge from the ground.
-fumarole in Halemaumau, Hawaii
-fumarole in Craters of the Moon, Idaho
-fumarole-Opal's
Pals
Galapagos Islands
-are a group of small shield volcanoes that
form islands in the eastern Pacific
Ocean.
glowing cloud eruption
-is an explosive, violent, red hot eruption
of a viscous silicic volcanic ash and
pyroclastics.
-glowing cloud eruption lecture
gravitational magmatic segregation
-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
Hawaiian volcanoes
-The Hawaiian islands are the tops of shield
volcanoes that were formed when
the Pacific plate
moved over
an active hot spot.
-Lanai,
a Hawaiian volcanic island
-map of the
Hawaiian islands
hot spot
-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.
-intrusion beneath the Escabrosa Limestone cliffs
island arc
-is a curved chain of volcanic islands
adjacent to an oceanic trench and
overlying a subduction
zone.
-map of the
Alaskan Aleutian island arc
laccolith
-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.
lava
-is molten rock that has erupted at the
earth's surface.
-lava flows in the Pinacates, Mexico**
-lava
flow burning trees
-lava
flow in Hawaii
-lava-Opal's
Pals
lava dome
-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.
-Lassen Peak-summit
lava flow
-is a single outpouring of a fluid lava.
-lava flows in the Pinacates, Mexico**
-lava in the crater of Haleakala, Maui, Hawaii
-multiple lava flows, Maui, Hawaii
lava lake
-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.
lava tube
-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.
-tour of lava tube under Mt. St. Helens
-tour of Thurston lava tube, Hawaii
(2012)
-lava tube in Maui, Hawaii
-exiting a lava tube
-collapsed lava tube-Rainbow Falls, Hawaii
-Idaho-Craters of the Moon-collapsed top of small lava tube
lunar maria
-are the large areas on the Moon covered by dark, basaltic lava flows.
maar
-is an explosive basaltic eruption that
produces a large crater.
-maars
in the Pinacates, Mexico*
-Cerro Colorado, Sonora, Mexico
-Crater Elegante, Sonora Mexico
-Paramore Crater, San Bernardino Valley,
Arizona
-maar-Opal's
Pals
magma
-is molten rock.
-magma-Opal's
Pals
magma mixing
-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.
Mauna Loa
-is an active shield volcano on the island
of Hawaii.
-Mauna Loa and Mauna Keas as seen from Maui
moat deposits
-are the volcanic materials deposited in the
moat lake within a resurgent
caldera.
-map view of the Valles caldera, New Mexico
Mt. Capulin
-is a cinder cone located in northern New Mexico.
Mt. Fuji
-is a composite volcano located in Japan
Mt. Fuji-You Tube video
Mt. Rainier
-a composite volcano, part of the Cascades,
located in the state of
Washington.
Mt. Shasta
-is a composite volcano, located in northern California.
Mt. St. Helens
-is a composite volcano, part of the
Cascades, located in the state of
Washington.
Mt. St. Helens Tour- Steve Tyminski-
Cochise College
Mt. St.
Helens- YouTube video
nuees ardentes volcanic eruptions
-are violent silicic eruptions often known
as glowing cloud eruptions
or ignimbrite eruptions.
-glowing cloud eruption lecture
pahoehoe lava flow
-is a relatively smooth surface lava flow;
often described as ropey
or bulbous.
-ropey
pahoehoe near Hilo, Hawaii
-surface of pahoehoe lava flow, Hawaii-1
-surface of pahoehoe lava flow, Hawaii-2
Paramore crater, Cochise County, Arizona
-is a maar type eruption located in the San
Bernardino volcanic field,
southeastern Cochise County,
Arizona.
Paricutin
-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
pillow lavas
-are underwater eruptions of basaltic lava
that form pillow-like shapes.
-pillow
lavas-Opal's Pals
pipe
-is a tube-like igneous intrusion, circular or elliptical in cross-section.
Pinacates volcanic field, Mexico
-is a volcanic hot spot in northern Sonora,
Mexico, consisting several
large maars, numerous
cinder cones, and fresh
appearing basaltic lava
flows.
pluton
-is an igneous intrusion.
-pluton-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
-map view of the Valles caldera, New Mexico
rim deposits
-consist of the volcanic ash deposited on
the rim of a crater from which
it was erupted.
Ring of Fire
-is the collection of volcanoes that are found encircling the Pacific Ocean.
San Bernardino Volcanic Field, Cochise County, Arizona
-is located in the extreme southeast corner
of Arizona and consists of basaltic
lava flows, small
cinder
cones, and a maar,
Paramore crater.
-San Bernardino-cinder cone
schlieren
-are bands of melted xenoliths that have not been completely mixed into the
magma.
These bands are commonly found near the outer margins of a
granite pluton.
-schlieren in granite, Mt. Whitney, California
-schlieren-Opal's Pals
seafloor spreading
-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
stock
-is a medium-sized, usually discordant
pluton that is between a pipe and a
batholith in size; less
than
forty square
miles.
-Sacramento stock in Bisbee, Arizona (pre-open pit mining)
stratovolcano
-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.
subduction zone volcanics
-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.
Valles caldera, northern New Mexico
-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.
-Idaho-Craters of the Moon-volcanic bomb-1
-Idaho-Craters of the Moon-volcanic bomb-2
-volcanic bombs-Haleakala, Maui, Hawaii
-Arizona-San Bernardino volcanic field-volcanic bomb-1
-Arizona-San Bernardino volcanic field-volcanic bomb-2
volcanic dome
-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.
-California-Lassen Peak summit
volcanic gases
-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
volcanic vent
-is where volcanic materials emerge from the
ground.
-volcanic vent in the Chiricahua Mountains of Arizona
volcano
-is a landform produced by the eruption of lava and ash from a single vent.
-Idaho-Craters of the Moon-cinder cone
welded tuff
-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.
-welded tuff in the Chiricahuas
-resurgent
caldera and welded tuff lecture
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
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