EES 150 exam 3 Flashcards
What has to be true for the cause of volcanoes due to Ocean-continent subduction zones?
.It has to be a continent
.Near a subduction zone
What has to be true for the cause of volcanoes due to Ocean-ocean subduction zones?
.It’s in the ocean
.Near a subduction zone
How did many people die by the Vesuvius volcano in Pompeii?
.Poisonous gas
.Buried by flows of hot ash
Is the Vesuvius volcano an volcanic islands or arc?
Volcanic arc
What 2 groups of people are most likely to get killed by volcanic activity?
.Volcanologist
,Photographers
What’s magma?
Melted rock material below the surface
What’s lava?
Melted rock that erupts at the surface
How is volcanic activity linked to tectonics?
.Magma chemical composition
.Ability to flow
.Gas content
.Volume
What factors are determined in whether a volcano is peaceful or explosive?
.Magma chemical composition
.Ability to flow
.Gas content
.Volume
What’s a volcano?
A place where lava flowed onto the surface whether it’s visible or not
What’s an active volcano?
A volcano that has erupted in historic times (or at least within the last 10,000 years)
What’s a dormant volcano?
A volcano that has not erupted recently but geologically is likely to do so again
What’s an extinct volcano?
A volcano that is geologically unlikely to erupt again
What form of rocks are volcanic rocks?
Igneous
Do volcanic rock have homogenous or heterogeneous appearance?
homogenous
Viscosity
Internal resistance to flow
Volatile
Abundance controls explosiveness (gasses escaping)
Volume
Influences severity eruption (small or large)
Nonexplosive eruptions
Icelandic & Hawaiian
Somewhat explosive
Strombolian
Explosive
Vulcanian & Plinian
Volcanic Explosivity Index
A way to evaluate eruptions of a scale of 1-8, according to 3 variables
Large VEIs have what
High volumes of ejecta
Flood basalts
Low viscosity, low volatiles, & very large volume.
Largest volcanic event and possibly the initial stages of a mantle plume
Causes of eruptions
Melting rock expanding in volume because of decrease in pressure
Gas escaping when magma rises
Global effects of flood basalts
CO2 & SO2 released into air
Why does flood basalts produce so much climate-changing gases
A lot of lava= a lot of gas
Icelandic-type eruption
Low water content & low viscosity (basalt). Very peaceful eruption from fissures and produces a “curtain of fire effect”
Example of Icelandic-type eruption
Krafla (1970s)
Hawaiian type eruption
Low water content & low viscosity (basalt). Higher lava fountain, low cones, and may last for years as lava flows slowly. Property may be destroyed
Main island of Hawaii includes what 5 volcanoes
Loa, Mauna, Hualalai, Mauna Kea, & Kilauea
Shield volcanoes
Low viscosity, low volatile, & large volume basaltic lava flows
Thin layers, very broad, great width compared to height
Phreatic eruption
Interaction of hot volcanic rocks and water (rare Hawaiian eruption)
Strombolian-type eruption
Short-lived explosion outbursts of pasty lava ejected 10s-100s m into air
Scoria Cones
Medium viscosity, medium volatility, & small volume
From through strombolian eruptions
(basaltic and andesitic lava)
Scoria cones are composed of what
Tephra (volcanic debris)
Where does the name Strombolian eruption come from
Stromboli volcano in Italy
Vulcanian-type eruption
Alternates between highly viscous lava flows and pyroclastic eruptions
Plinian-type eruption
Produce gas-powered vertical columns of pyroclastic debris up to 50 km into atmosphere
Starto-
Layered
Stratovolcanoes
Result of high viscosity, high volatiles, large volume from vulcanian to plinian eruption, gas-rich andesitic to rhyolitic magma
Stratovolcanoes are found where?
At subduction zones where magma is generated
Volcano weather
Steam cools, condenses, and falls as rain
lahars
Rain mixing with ash on volcano’s slopes
Volcano weather can produce…
lightning
Volcanic ash from plinian eruptions is hazardous to…
airplanes
lava domes
high viscosity, low volatiles and small volume eruptions that happen after Vulcanian/Plinian eruption
lava domes and low volatiles
Gases escape during the larger eruption and the low-gases left cools in place forming a plug
Why has a lava dome formed inside the crater of Mt. St. Helens?
Because the gas is gone
A typical stratovolcano eruption sequence
Vulcanian precursor -> Plinian main event -> lava dome conclusion
Vulcanian precursor
Gas- rich material shoot out first
Plinian main event
Gas depletes
Lava dome conclusion
High-viscosity magma build lava dome
Calderas
Result from high viscosity, high volatile, and very large volume
Where are calderas?
The summit of volcanoes and collapse of a stratovolcano
Giant continental calderas are associated with what?
Mantle plumes
Resurgent Caldera form where?
Where calderas have preciously formed
Where do magma erupt at mantle plumes?
Material comes from the Earth’s melted center
Columbia river plateau basalt
River has eroded down through them in many places
Cycle of mantle plumes
Early on mantle plumes spread out and is very hot; later it cools down and affects a smaller area
Oceanic plateau
A massive flood basalt from a mantle plume beneath an oceanic plate
Eruption styles and frequencies between California and Hawaii
California- continental crust
Hawaii- Oceanic crust
Most active volcano in Hawaii
Kilauea
Iceland is on what?
Mid-ocean ridge (above sea level) & mantle plume
Shallow earthquakes are associated with what?
Movement of magma
Volcanic eruption in 1973, Island of heimaey & it’s harbor
Lava flow blocked harbor, part of town buried, & 5.5 billions tons of sweater used to cool and redirect lava flow
What’s responsible for opening up the North Atlantic?
Iceland mantle plume
Plutonic igneous rocks
Cool slowly below the surface
Volcanic igneous rocks
Cool quickly at/ near the surface
What elements are abundant in the composition of magma?
Iron- Oxygen-> Silicon-> Magnesium-> other
Why do igneous rocks and magmas have different compositions?
.Magma mixing
.Melting of surrounding rock & incorporation into magma body
.Partial melting
.Fractional crystallization
Partial melting
Where low temperature minerals melt first
Where do volcanoes form?
.At subduction zones(10%)
.Mantle plumes(10%)
.Mid-Ocean ridges(80%)
How does magma from mid-ocean ridges form?
Partial melting due to the mantle due to lower pressure
How does magma from mantle plumes form?
Partial melting due to the mantle eventually causing a mid-ocean ridge to form or overriding plate
Where are volcanoes usually not found?
.continent-continent convergent plate boundaries
.Transform plate boundaries
Pyro-
fire
-clastic
broken up
What’s one control on viscosity?
temperature
What makes an eruption more explosive?
Dissolved gases (including water)
3 types of magma/lava
Rhyolitic, Andesitic, & Basaltic
Basaltic lava
Highest temperature, lower SiO2, low viscosity, low gas, erupt peacefully, frequent, flows long distances, low pressure, & lower minerals melting points
Where does basalt form?
Mid-ocean ridges
Andesitic/ Rhyolitic
Lower temperatures, higher SiO2, more viscous, dangerous eruptions, high gas, lava flows slowly and not far, presence of water, & partially melting oceanic crust
What produces andesitic lava?
Partially melted basaltic oceanic crust at subduction zones
Rhyolitic magma
Highest gas and erupts explosively
Calcium/Sodium rich minerals depend on what?
temperature
Which lava has the most complex arrangement of bonded silica tetrahedral?
Andesitic/Rhyolitic
Example of Basaltic eruptions
Mauna Lao, Hawaii
Features of Basaltic eruptions
Pahoehoe, A’a, Lava tubes, Columnar jointing, System of Polygonal Cracks
Pahoehoe
Flows hot lava beneath the skin & the skin just piles up while cooling
A’a
Lava flows farther away from volcano when it’s cooled down, thicker crust & lava still flows, & lava breaks and deform
Lava tubes
Cools more quickly but lava continues to flow beneath
How does a lava tube form?
Cooling (crystalizing) forms crust above it and lava tube becomes a cave
Columnar jointing
Are results as basaltic lava flows & contract (looks supernatural) that have equally spaced centers
System of Polygonal Cracks
Lava cools & decease volume
Volcanic neck
Lava that cooled & crystallized inside a volcano that can be seen after the outside layers of the extinct volcano have eroded away
Andesitic/Rhyolitic volcanoes form near?
Subduction zones
Features of Andesitic/Rhyolitic eruptions
Pyroclastic debris, volcanic ash, tuff/ tephra, pyroclastic flow, & volcanic gases
Pyroclastic debris include
Volcanic ash, bombs, Lahar, & blocks of pre-existing volcano
Bombs
Large blobs of lava
Volcanic Ash
Little shards of lava that form a glasslike substance. Shattered rock
Pyroclastic flow
Fast moving avalanche of hot tephra
Tephra/ Tuff
A deposit of pyroclastic material which welds together to form the rock Tuff
Lahar
When tephra mixes with water causes deadly flow (like muddy water)
Volcanic gases
Water, Co2, H2S, SO2
Vescular texture
Gas bubbles escaping from cooling lava
What do volcanoes make the most of on Earth?
Water
Mantle Plume melting
Partial melting on mantle, partial mantle on crust, or complete melting of crust
Triggers of mantle plume melting
Deceased pressure, rocks rise, & expansion of volume
Icelandic composition
Low water & viscosity (basalt)
Hawaiian composition
Low water & viscosity (basalt)
Strombolian composition
Moderate water & low to moderate viscosity (basalt to andesite)
Vulcanian composition
Moderate to high water & moderate to high viscosity (basalt to rhyolite)
Plinian composition
High water and viscosity (Andesite to rhyolite)
What are the 4 primarily ways to volcanoes and kill?
Pyroclastic flow
Tsunami
Lahar
Indirect (famine)
Why does Pyroclastic flow happen?
.Eruption column collapse
.Collapse of a dome
.Overspilling the crater rime
.Direct blast of pyroclastic material
Mt. Pelee
Pelee- peeled or baled
St. Pierre
Completely destroyed
2 survived
Stayed because of election
nuee ardente
Glowing cloud
Glowing cloud refers to…
Hot, glowing volcanic fragments, & 700 degrees Celsius when it hit St. Pierre
Volcanoes that produce pyroclastic flow
Rhyolitic
Santa Cruz volcano
No subduction zone
Mantle plume
Krafla volcano
Fluid lava
Lewatobi Volcano
Subduction zone
Andesitic
Other ways of volcanic deaths
Gas
How are craters formed?
Volcanic gases
Climate changes caused by volcanoes
.Volcanic ash-> global cooling
.Sulfuric acid-> acid rain
.CO2-> global warming
