Exam 3 Flashcards
2 types of igneous rocks
extrusive and intrusive
extrusive igneous rocks
volcanic
intrusive igneous rocks
plutonic
What do igneous rocks erupt?
lava and pyroclasts
Fragmented volcanic rock ejected upward explosively
pyroclasts
pulverized magma also a type of pyroclasts
ash
molten rock in the earth
magma
magma that reaches the surface
lava
3 parts of characteristics of magmas
- Composition
- Viscosity
- Volcanic Gases
Compositions
what something is made up of
What is the overall composition of magmas?
made of silica
Silica minerals are made of
silicon and oxygen
What are the 3 types of compositions of magmas?
- Mafic
- Felsic
- Intermediate
Mafic is ____ poor
silica
Why is mafic dense
because of minerals
Felsic is what type of composition
silica rich
Felsic has a high amount of
gases
Felsic rocks
rhyolites
light, less dense rock
rhyolites
Intermediate silica content
intermediate
rocks of intermediate composition
andesites
Andesites are found in
the Andes
Where are andesites abundant
over subduction zones
The resistance to flow
viscosity
Viscosity is controlle by
silica content and temperature
Higher temp = ___ viscosity
less
Something that doesn’t resist flow
has a low viscosity
Mafic magma viscosity
silica poor, very hot = low viscosity
Felsic and Intermediate magmas viscosity
silica rich
cooler = higher viscosity resists moving
2 most abundant volcanic gases
H2O and CO2
Once an eruption starts the pressure is _____ and drive the explosion _____.
lowered; upward
Why do you want to avoid dead tree areas in Mammoth?
volcanic gases are escaping to the surface and you could breath CO2
Lake Nyos is a lake on top of what
active volcano structure
Everything killed without a volcanic eruption
lake nyos
Magmas: Hot, silica poor and low viscosity
Mafic
Result of a mafic magma
fluid eruption and lava flow
Magma: Silica rich, cooler, high viscosity
Felsic and Intermediate magmas
Result of felsic and intermediate magmas
explosive eruption with pryoclasts
Pressure decrease
mid-ocean ridges
water added
subduction zones
heat added
hot spots
What is important to allow plates to move?
Lower pressure
What is a catalyst for melting rocks?
Water
Where are the majority of land volcanos?
at subduction zones, in the pacific rim of fire
Which kinds of eruptions are the most hazardous?
Pyroclastic Eruptions
Opening of a volcanic edifice (1km or less)
Crater
Opening of a volcanic edifice, larger than 1km
Caldera
Volcanic building connected to magma chamber below crater
volcanic edifice
Mt. Pinatubo is an example of what
caldera
Phillipines and Mt. Tambora are examples of what
Calderas
One possible cause of the information of a caldera
summit collapse
Volcano: Broad dome, gentle slope and very large
Shield
Volcano: Composition of basaltic lava flows
shield
Volcano: fluid magmas with low viscosity and low silica
Shield
Volcano: Basaltic, mafic and largest
Shield
2 Examples of shield volcanos
Hawaii and Iceland
Hawaii is a
hot spot
Iceland is a
mid-ocean ridge
Volcano: Steep, tall and layered
strato
Volcano: composition of andesite lava flows
strato
Volcano: pyroclastic and lava flows
Strato
Volcano: high viscosity and high silica
Strato
Volcano: Andesites, rhyolites, basalts
Strato
2 nd largest volcano
Strato
Mt. St. Helens is an example of
strato volcano
Mt. Vesuvius is an example of
strato volcano
Mt. Rainer and Mt. Fuji are examples of
strato volcano
Mt. Hood in Oregon and Mt. Shasta are examples of
strato volcanos
Land slides and toxic gases are hazards associated with
Strato Volcanos
Lava dome collapse and acid rain are hazards associate with
Strato volcanos
Lava flows and ash falls are hazards associated with
Strato Volcanos
Type of flows associated with Strato Volcanos
pyroclastic and mudflow (lahar)
Crater Lake in oregon collapsed
inwards (summit collapse)
Crater Lake in Oregon is approximately
10km
Crater lake in Oregon is filled with
water
Is Crater Lake in Oregon active or inactive?
active
What type of cone is Crater Lake in Oregon
Cinder cone
Pacific Northwest volcanoes are a result of the ______ and occurs at ______
Juan de Fuca Plate; Subduction Zones
The shape of volcanoes is controlled by what it
spits out
Cone that is steep, small and short lived
Cinder cone
Cinder Cone is a ______ pyroclasts composition
basaltic
Cinder cones occur adjacent with
other big volcanoes
Viscosity of cinder cone
viscous
From largest to smallest volcanoes
Shield –> Strato –> Cinder
What kind of cone was a Paricutin eruption, Mexico?
Cinder cone
What kind of flow is paricutin eruption, mexico?
lava flows
Is Paricutin eruption, mexico active?
not active anymore
Volcanic Explosivity Index is from what to what numbers?
0 to 8
Powerful vertical ejection of pyroclasts, gas
plinian
Most explosive eruption
Plinian
Plinian eruptions VEI range
3 to 8
Where are plinian eruptions common over
strata volcanoes
What type of eruption has a small eruption of pyroclasts?
Strombian
What type of eruption is a fluid basaltic lava flows?
Hawaiian
Yellowstone is so big that we call it
a collapse caldera
Yellowstone is a result from
a continental hotspot
Why are geysers erupting in Yellowstone?
because there is so much heat
When yellowstone emptys its magma all of it goes out then collapses downwards then refills
catastrophic summit collapse
Anak Krakatau, Indonesia
- cinder cone
- pyroclast type eruptions
Crater lake
- cinder cone inside a strato peak
- still active
Santorini
- Lost city of Atlantis
- Caldera
Today Atlantis looks like
a crater lake
City on top of active volcano
Phira
Here lavas are really fluid, hot and low viscosity
Hawaii
example of mafic composition
Hawaii
How many big shield volcanos in hawaii
5
Most active volcano in the world
Kilauea
What des Mauna Loa have?
calderas because they are over 1km in width
Dormant and going to be extinct, it moved from the source of lava
Mauna Kea
Why is Mauna Kea not active?
because it has stepped out of the hot spot
2 shielf Volcanos in Hawaii
- Kilauea
- Mauna Loa
In the future there will be a new island in the south called?
Loihi
Hawaii has what types of volcanos
Strato, shield and calderas
2 deadliest volcanic hazards?
pyroclastic flows and volcanic mud flows
When the column decides to collapse outwards this causes
pyroclastic flow
Scalding avalanche of ash and toxic, expanding gases
pyroclastic flow
2 ways to make a pyroclastic flow
dome and column collapse
Viscous lava that grows on the inside the crater of volcano
Dome
Dome collapse is a cause of
pyroclastic flows
Dome collapses are quite
unpredictable
When a pyroclastic column starts to go up and then comes down
Column collapse
Full plinian column comes down and incinerates everything in its path
Column collapse
Which are the most deadly volcanoes?
Strato
Examples of Strato pyroclastic flows? (4)
- Mt. St. Helens
- Mt. Pineatube
- Mt. Montserrar
- Mt. Mayon
A flood flow of ash
Volcanic mud flow or lahar
Rapid flood of pyroclasts and water
lahar
- Rainfall and loose ash
- Melting of snow and ash
- Breakout of a crater lake
- Rivers and lakes
Causes of Lahar
In Mt. St. Helens the ____ plate is ____ under the ____ plate
- Juan de Fuca
- Subducting
- North American
In Cascadia subduction one the volcanoes are young or old?
quite young
Recurrence interval of Mt. St. Helens
around 200 years
The eruption of Mt. St. Helens was similar to
500x the force of the Hiroshima explosion bomb
- Swarms of EQs
- Steam/ ash explosions
- M= 5 EQ
- VEI = 5
- Gigantic landslide
- steam blast
- mudflows
- plinian column with pyroclastic flows
Precursor Events of Mt. St. Helens
Death toll of Mt. St. Helens
57 people
What remains after explosion
a caldera
Why did the Mt. St. Helens volcano not catastrophically collapse?
because the Magma chamber did not fully empty
and this is common event as opposed to summits collapse
What hazard can a dome produce?
a pyroclastic flow
In Nevado del Ruiz what plates are involved?
Nazca plate is subducting under the South American Plate
_____ overcomes friction in a mass waste
gravity
Tectonic forces ____ uplift the ground and are seen at subduction zones
uplift
Where do Tectonic forces occur?
in the Cascades on the East Coast
Solana Beach
is a disaster waiting to happen because coastal erosion is occurring
- Soft loose sediment and silts erode very rapidly and that is how the beaches form in CA
- People are building on these cliffs
- People carve out notches and ruin the base. Do not stand at base of cliff
Hazards in Solana Beach
What are the 5 factors of mass wasting?
- Water content
- Slope angle
- Geological
- Human
- Vegetation
excess water increases slope failures
water content
Steep slopes increase slope failures
slope angle
til of rocks, types of rocks, clay, faults
Geological
Overloading of slopes, artificial fill, excavation of highways and deforestation
Human
Decreases slope failures
Vegetation
Water is ____ from soil in vegetation. They provide ___and ___. The only thing that is good
- removed
- cushions
- cover
3 types of mass wasting
- Falls
- Slides
- Flows
Free fall of rocks; very rapid and common in mountains
Rock fall
movement of rock down a failure
Slides
Slump (rotational slide)
curved surface, weak sediments, small
Rockslide
planar surface, more coherent
La Jolla is a
slump
Most fluid and it results from very heavy rainstorms
Mud flow
Volcanic mud flow; comes from rain, lake, river
Lahar
Largest, fastest and most deadly flow, also very rare. Encompass huge areas
Debris Flow
Slow moving, not very harmful but can lead to other types of mass wasting
Creep
Triggering Events for mass wasting
- Rainstorms
- Earthquakes
- Volcanoes
Product of a large earthquake off shore
Yungay, Peru
Nazca plate is sliding under the south american plate
Yungay Peru
Yungary, Peru is on a
convergent boundary
Yungary, Peru was triggered by
subduction quake of M=7.7
Yungary Peru was a compositie event of
rock fall and flow
