Vocanoe Flashcards
Magma in shield volcano
Basaltic (mafic)
Magma in Composite/Stratovolcano
Andesitic (intermidiete)/basaltic/granitic
Magma in Cinder Cone volcano
Granitic/Rhyolitic (felsic)
amount of silica in shield volcano
low (Makes lava more flowy)
amount of silica in Composite volcano
mid (lava less flowy)
amount of silica in cindercone volcano
high (Lava sticks together)
Color of Shield volcano
Mafic (dark colored due to magnesium and iron)
Color of Composite
Intermediete
mixed
Color of cindercone volcano
Felsic (light in color- white/ pink/ gray)
Shield volcano eruptiono
-Quiet eruptions
-fissure (crack in rock) eruptions form ¨flood basalts¨ instead of cone shaped mountains
Composite volcano eruption
-Vary between quiet and violent (mediumvolatility)
-depends on the amount of silica and water vapor
Cindercone volcano eruption
Big violent explosion
More silica, more visous
Relase the pressure with big explosion
Location of magma- Shield volcano
both oceanic and continental crust
Location of magma- composite volcano
continental margins asociated with subduction zones
Location of magma- cinder cone volcano
continental crust
Gas content- shield volcano
1-2% low
Gas content- composite volcano
3-4% in between the amt
Gas content- cindercone volcano
4-6% high amount
Viscosity-shield volcano
low
Viscosity-composite volcano
intermidiate
Viscosity-cinder cone volcano
high
iron-shield volcano
rich in iron
iron- composite
medium
iron- cinder cone volcano
little to none
source material-shield volcano
upper mantle
source material-composite volcano
oceanic crust and oceanic sediments
source material-cinder cone volcano
continental crust
plate boundary- shield
divergent
plate boundary-composite
convergent
plate boundary- cinder cone
convergent
sill
magma that squeezes into parallel cracks between rock layers and then hardens
dike
magma that squeezes into vertical crack between rocks and then hardens
batholiths
The largest intrusive rock formations are
Rocks that form when magma cools underground
intrusive
If the top of a volcano collapses it may form a large opening called
caldera
ship rock new mexico is an example of a
volcanic neck
crater lake in wyoming is an example of a
caldera
volcanic neck
when erosion wears a volcanic cone away it leaves behind a volcanic neck
the granite domes of national yosemite national park are the remains of a large
batholith
volcano
an opening in Earth that erupts gases, ash, and lava.
Volcanic mountains form from
layers of lava, ash, and other material.
world most active volcano
mt kilauea
The Hawaiian Islands were formed by
such a hot spot occurring in the middle of the Pacific Plate.
Where is one of the most active volcanic areas and why?
Iceland due to its location on the Atlantic divergent boundary
hotspot or mantle plume
an upsurge of abnormally hot rock in the Earth´s mantle.
Iceland formed by
by the coincidence of the spreading boundary of the North American and Eurasian plates
effects of eruptions
Falling volcanic ash can collapse buildings, block roads, and can cause lung disease in people and animals destroying everything in their path.
Pyroclastic flows are composed of
super-hot volcanic ash, cinders, bombs, and other debris rush down the side of the volcano
how does acid rain form
when sulfurous gases mix with water vapor in the atmosphere
*Ash and other debris can choke rivers and clog plant pores, killing vegetation.
- Global cooling occur is cauased by microscopic particles.
- Other gasses also cause ozone destruction.
crater
steep walled depression around a vent
volcanic vent
an opening in earths crust through which magma is released
fumarole
type of vent where steam, water vapor, sulfur dioxide, hydrochloric acid are emitted
Magma
molten rock below earth surface
lava
molten rock flowing on earths surface
Where do volcanos form
They form at divergent, and convergent plate boundaries and hot spots
Divergent plate boundary volcanoes
plates move apart, as more lava hardens, it build up on the seafloor
What do divergent plate boundaries form
rift volcanoes
Convergent plate boundary volcanoes
2 plates move together & collide denser plate sinks or subducts into the mantle.
Volcanoes at convergent plate boundaries are violent.
As the Pacific Plate continued to move.
the islands of Oahu, Molokai, Maui & Hawaii were formed. The Hawaiian Islands formed over a period of about 5 million years
what makes a volcanoes active
must have erupted in the last few thousand years
How many active volcanoes r there and how many erupt a week
1,500, 15-20
how many volcanoes erupt that were previously thought to be dormant or extinct.
2-3
how to predict if a volcano will erupt.
Scientists continue to monitor the shape of the volcano, changes in the composition of gases, and even changes in the pattern & intensity of earthquakes
Where does the United States rank in the number of volcanoes?
The United States ranks 3rd behind Indonesia and Japan, in the number of historically active volcanoes
Two factors that control eruptions:
The amount of water vapor and other gases.
How much silica is present in the magma.
Trapped Gasses
*Surrounding rock layers, magma, and trapped gasses causes a buildup of pressure.
*As magma rises, pressure decreases and water turns into steam that can propel the eruption. Eventually gas mostly of water & CO2 eventually escapes and causes explosive eruptions.
Wet Magma
- magma that has a lot of water vapor at some convergent boundaries & can cause explosive eruptions when the oceanic plate slides another plate
silica thickness
the more the thicker and the less the thinner
water content
the more gas (water) the high pressure and more explosive and vice versa
Basaltic magma eruptions
low silica, gas can easily escape, quiet, and nonexplosive, ex, kilauea
Where do Basaltic magma eruptions occur, (plate boundary)
hot spots and divergent plate boundary
Quiet Eruptions has 2 types of lava flows on land
pahoehoe (rope-like with smooth surface; flows well)
aa (lower temperature; stiff & rough surface)
lava fountins
trapped gases in basaltic Magma that can escape easily
pillow lava
basaltic lavas that flow underwater
Lava that comes out of cracks of the ocean floor
Pillow lava
What magmas have the greatest explosion
Rhyolitic magmas have the greatest explosion because they have high silica, high viscosity & high gas content.
Granitic and andesitic volcanoes are usually found at…..because ………
the ocean-continent or ocean-ocean convergent boundaries bc as Magma moves up, it melts silica-crust and becomes silica enriched
felsic ex
granite
maffic ex
gabbro
Basaltic magma- viscosity, gas content,silica content, explosiveness, and location of magma
Low, 1-2%, 50%, least, Both oceanic and continental crust
andesitic magma- viscosity, gas content,silica content, explosiveness, and location of magma
intermediate, 3-4%, 60%, intermediate, continental margin accosiated with subduction zones
Rlhyolitic magma- viscosity, gas content,silica content, explosiveness, and location of magma
high,4-6%,70% greatest, continental crust
Tephra
bits of rock or solidified lava dropped from the air, cools and hardens: varies in size from volcanic ash to cinders, to larger rocks
Composite volcanos
emit a stiff rapidly solidifying lava which forms high, steep, sided cones
cinder cone volcanoes
Regularly throw out ash and build up flatter domes called cinder cones
shield volcanoes
lava does not eject violently, but flows over crater rimforming a broad low profile
supervolcano and 2 examples
Supervolcano has a Volcanic Explosivity Index (VEI) of 8.
and are characterized as volcanic centers that have had eruptions that covered more than 240 cubic miles. The US has two: one at Yellowstone and another at Long Valley in California.
lahars
Mudslides made up of volcanic materials. They usually move at speeds 20-40 mph, but can be up to 50 mph. They are one of the deadliest volcanic hazards because they can occur even when a volcano is not erupting. They occur on snow/ice capped volcanoes.
What triggers a volcanic landslide?
It can be triggered by eruptions, heavy rain, earthquakes, and even just small movements of loose debris
Where do volcanic landslides occur?
They occur on steep sided volcanoes
volcanic landslides
Volcanic landslides are just like regular landslides except they occur on volcanoes and with volcanic material (rock fragments, debris, etc.)
What are pyroclastic surges?
“Low density pyroclastic flows [that] can easily overflow ridges”
pyroclastic flows
When the substances inside the volcano (ash, rock fragments, gas) flow down the volcano at intense speeds and high temperatures.
Which type(s) of lava cause lava domes?
Andesitic and Granitic (rhyolitic) lava
What are lava domes?
Irregular mounds at the top of a volcano formed by viscous lava with a high concentration of silica
When do volcanoes emit gases?
All the time (even when the volcano is not erupting)
Why are eruption columns and clouds dangerous?
They can grow very quickly and very high. They can be dangerous to planes flying through them, collapse buildings, damage, crops, and damage electricity and machinery.
What are eruption columns and clouds made of?
It is made up of solid particles (dust)
caldera ex
kilauea
