Chapter 5 Flashcards
A viscous fluid
- resists flow
viscosity
- controls whether magma flows away or piles up
volatiles
- controls the explosively of an eruption
volume
- controls the intensity of an eruption
Identify the correct characteristics describing Strombolian-type eruptions
- strombolian-type eruptions are typically intermittent
- Strombolian-type eruptions are not strong enough to destroy scoria cones
A _____ is a large volcanic depression formed by roof collapse into a partially emptied magma reservoir
- caldera
Plinian-type eruptions are characterized by ____
- the generation of a sustained gas-powered eruption column that carries pyroclastic material high into the atmosphere
The two most abundant elements of the Earth’s crust are ____ and _____.
- oxygen and silicon
Typical eruption sequence
- gas rich materials blast out during a Vulcanian eruption
- longer-lasting, gas-driven pinion eruption generates a sustained eruption column.
- gas-poor, high viscosity magma oozes out of form a lava dome.
three ways in which rock may melt
- addition of water
- increasing the temperature
- lowering the pressure
shield volcano
- low viscosity, low volatiles, large volumes
scoria cone
- low/medium viscosity, medium/high volatiles, small volume
stratovolcano
- medium/high viscosity, medium/high volatiles, large volume
lava dome
- high viscosity, low volatiles, small volume
What do you call a relatively small volcano constructed of pyroclastic debris piled around a central vent?
- scoria cone
Which of the following are common features of Hawaiian-type eruptions?
- lava flows
- lava fountains along fissures
- buildup of a low cone with fountain eruptions
Which of these descriptions best describes a Vulcanian eruption?
- a sustained eruption column of hot gases and pyroclastic material that climbes to several kilometres in the atmosphere.
Characteristics describing strombolian-type eruptions
- strombolian-type eruptions are not strong enough to destroy scoria cones
- Strombolian-type eruptions are typically intermittent
Which of the following is a feature created by explosive volcanism?
- lava dome
The “three v’s” of volcanology are ___, _____, and ____.
- viscosity, volatile, volume
Rank the following volcanic rocks in order of increasing viscosity: basalt, rhyolite, andesite
1) basalt
2) andesite
3) rhyolite
____ melting occurs when mantle rocks rise upward and experience lower pressure.
- decompression melting
Which type of volcanic eruptions create stratovolcanoes?
- Vulcanian and plinian eruptions
Another name for a stratovolcano is a ____.
- composite volcano
Which plate tectonic settings are associated with volcanic activity?
- subduction zones
- continental rifts
A huge eruption of large volumes of viscous magma that generates high ash columns and widespread sheets of outward-flowing ash and pumice is called a ____ eruption.
- ultra-plinian
What is the main driving force of explosive volcanic eruptions?
- volcanic gases coming out of magma
A typical shield volcano is composed primarily of ____.
- solidified basalt lava flows
A ____ is a large volcanic depression formed by roof collapse into partially emptied magma reservoir
- caldera
A volcano that has not erupted for a long time but is not extinct is referred to as being _____, which means sleeping.
- dormant
Ninety per cent of volcanism is associated with ____.
- plate boundaries
What is the main difference between Icelandic-type and Hawaiian type volcanic eruptions?
- volume of magma
What distinguishes a caldera from a crater?
- greater than 2 km in diameter
- formed by inward collapse
What is the eruptive sequence of a resurgent caldera? (in chronological order)
1) rising magma causes a bulge on the Earth’s surface
2) ultra-plinian volcanic eruption
3) caldera collapse
4) formation of a resurgent dome
What features are common of Hawaiian-type eruptions?
- lava flows
- buildup of a low cone with fountain eruptions
- lava fountains along fissures
What do you call a relatively small volcano constructed of pyroclastic debris piled around a central vent?
- scoria cone
Which landform is most often associated with Hawaiian-type eruptions?
- shield volcano
Eruptive sequence of a resurgent caldera
- rising magma causes a bulge on the Earth’s surface
- ultra-plinian volcanic eruption
- caldera collapse
- formation of a resurgent dome
Which landform is most often associated with Icelandic-type eruptions?
- lava plateau
Which of the following best describes a stratovolcano?
- a large volcano composed of alternating layers of pyroclastic fragments and solidified lava flows
Which of the following best describes a cinder cone?
- a relatively small cone constructed of pyroclastic debris piled up next to a central vent
Which of these eruption styles are most closely associated with stratovolcanoes?
- Vulcanian
- plinian
What is obsidian?
- a volcanic glass
Another name for a stratovolcano is a ____
- composite volcano
What best describes the nature of magma that forms a lava dome?
- high viscosity
- low volatiles
A new mass of rising magma that bows up the caldera floor following a caldera eruption is called a _____.
- resurgent dome
Characteristic of pahoehoe lava flows
- they form in fluid lava
In what way do lava domes present hazards?
- gravity-driven landslides can be generated from the steep slopes of lava domes
- lava domes can plug a volcanic vent, allowing pressure to build, which leads to a violent eruption.
What increased the risk posed by Vesuvius?
- a large number of people live close to the volcano
What drives melting at subduction zones?
- release of water into the mantle, lowering its melting temperature.
More tha 80% of Earth’s magma is erupted at ____.
- spreading centres
The basalt flows that compose a shield volcano typically _____, which results in great slopes.
- flow for a long distance, firming thin flows.
Why is volcanism not generally associated with transform faults?
- mantle material is neither rising nor sinking at transform boundaries; the plates are simply sliding past each other.
What type of lava flow is most likely to exhibit flow wrinkles at the surface?
- pahoehoe
What do you call a relatively small volcano constructed of pyroclastic debris piled around a central vent?
- scoria cone
Why does melting occur at spreading centres?
- pressure decreases as mantle material rises upward
Tall, conical volcanoes are associated with what type of plate boundary?
- subduction zones
Identify the type of the 79 BC eruption of Vesuvius
- plinian eruption
In what way do lava domes present hazards?
- gravity-driven landslides can be generated fro the steep slopes of lava domes
- lava domes can plug a volcanic vent, allowing pressure to build, which leads to a violent eruption
What is the main hazard associated with Hawaiian volcanism?
- destruction of property and infrastructure by lava flows
The caldera-forming eruption of ____ in 1628 BCE is believed to have led to the collapse of the Minoan civilization
- santorini
Flood basalts
- vast outpourings of basaltic lava from fissures that do not build a central volcano
Example of a giant continental caldera
- yellowstone
The most explosive and dangerous volcanoes are generally found at _____.
- subduction zones
The people who remained at Pompeii during the eruption of Vesuvius in 79 CE were killed by
- ash and pumice that fell on the town
Example of a shield volcano
- Mauna Loa, Hawaii
Where do plutonic and volcanic rocks form?
- plutonic rocks form in the subsurface and volcanic rocks form on the Earth’s surface
Magma at deep depths does not contain
- gas bubbles
The Volcanic Explosivity Index (VEI) takes into account the following factors:
- duration of the major eruptive blast
- height of eruption column
- volume of material extruded
Why do volcanic bombs often exhibit an aerodynamic shape?
- they solidified while airborne
Example of a scoria cone
- Paricutin, Mexico
The spectacular spine that formed on ____ in the Carribbean, after its deadly 1902 eruption, is an example of a lava dome.
- Mount Pelee
When magma reaches the Earth’s surface, it becomes
- lava
People near the sea during the 79 CE eruption of Vesuvius were mostly killed by ____.
- pyroclastic flows
Examples of stratovolcanoes
- Mount Kilimanjaro, Tanzania
- Mount Fuji, Japan
- Mount Rainier, Washington
- Mount Shasta, California
aa
- a lava flow with a rough, blocky surface
active volcano
- a volcano currently erupting or that has erupted in historical times; for example, Kilauea, Hawaii; Krakatu, Indonesia
andesite
- a volcanic rock named for the Andes Mountains in South America
- it is intermediate in composition between basalt and rhyolite, and commonly results from melting or continental rock in basaltic magma
basalt
- a dark, finely crystalline volcanic rock typical of low viscosity oceanic lavas
BCE
- before common era
caldera
- a large (over two kilometres in diameter), basin-shaped volcanic depression, roughly circular in map view, that forms by a piston-like collapse of rock into a partially evacuated magma chamber
crystallization
- the growth of minerals in a fluid such as magma
crater
- an abrupt basin commonly rimmed by ejected material
- in volcanoes, craters form by outward explosion, are commonly less than two kilometres in diameter, and occur at the summit of a volcanic cone
decompression melting
- the most common process of creating magma
- melting occurs by reducing pressure on hot rock
dormant volcanoes
- volcanoes that have erupted during the last several thousand years but have been quiet in historical times; for example, Mount Meager, British Columbia.
extinct volcano
- a volcano that has not erupted during the last several thousand years and is not expected to erupt again; for example, Kilimanjaro, Tanzania
fissures
- narrow cracks in rock
flood basalts
- tremendous outpouring of basaltic lava that formed tick, extensive plateaus in the geologic past
lahars
-mudflows composed of unconsolidated volcanic debris and water
lava
- magma that flows on the Earth’s surface
lava dome
- a mountain or hill made from highly viscous lava, which has plugged the central conduct of a volcano
magma
- molten rock material
- it solidifies on the Earth’s surface as volcanic rock and at depth as plutonic rock
mineral
- a naturally formed, solid inorganic material with characteristic chemic composition and physical properties that reflect an internally ordered atomic structure
obsidian
- dark volcanic glass
plinian eruption
- a type of volcanic eruption where an immense column of pyroclastic debris and gases is blown vertically to great heights
plutonic rocks
- rocks formed by the solidification of magma deep below the surface
pumice
- volcanic glass so full of holes that it commonly floats on water
pyroclastic
- pertaining to magma and volcanic rock blasted up into the air
pyroclastic flows
- high temperature, fast-moving clouds of fine volcanic debris, steam, and other gases; also called anuee ardente
resurgent caldera
- a large topographic depression formed by a piston-like collapse of rock into a magma chamber with a later central uplift of the caldera floor
resurgent domes
- the uplifted floors and masses of magma in the centres of large volcanic calderas
rhyolite
- a volcanic rock formed from high viscosity magma and typical of the continents
scoria cones
- small cone or horseshoe shaped hills made of pyroclastic debris from Hawaiian or Strombolian type eruptions
- they commonly occur in groups
shield volcanoes
- very wide volcanoes built of low viscosity lava
stratovolcanoes
- volcanoes constructed of alternating layers of pyroclastic debris and lava flows; also called composite volcanoes
ultra-plinian
- a type of volcanic eruption characterized by exceptionally large outpourings of pyroclastic material in high eruption columns and voluminous ash-flow sheets that cover wide areas
volatiles
- substances that readily become gases when pressure is decreased, or temperature increased
volcanic rocks
- rocks formed by solidification of magma at the Earth’s surface
