Chapter 12 Flashcards

1
Q

volcanic geosystem

A

the rocks, magma, and processes needed to describe the entire sequence of events from melting to eruption

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2
Q

three types of lava

A

basaltic
andesitic
rhyolitic

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3
Q

basaltic lavas

A

most common magma type
product of mantle melting
erupt when hot, fluid magmas fill up a volcano’s plumbing system and overflow

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4
Q

pahoehoe

A

forms when a highly fluid lava spreads in sheets

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5
Q

andesitic lava

A

lower temperatures than basalts

higher silica content - flow slower

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6
Q

rhyolitic lava

A

lowest melting point

richest in silica

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7
Q

tuffs

A

rocks created from smaller fragments such as ash

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8
Q

breccias

A

rocks created from larger fragments

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9
Q

types of central-vent volcanoes

A
shield
domes
cinder cones
stratovolcanoes
craters
calderas
diatremes
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10
Q

shield volcano

example

A

occurs when basaltic lava flows create a shield-shaped volcano 2+ kilometers high and tens of kilometers in circumference
example - Mauna Loa

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11
Q

volcanic dome

A

occurs when andesitic and rhyolitic flows (very viscous) are essentially squeezed out of the volcano with very little lateral spreading

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12
Q

cinder cones

A

these are created when volcanic vents discharge pyroclasts that build up to create a cone
vent can become filled with volcanic debris that falls down the slope

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13
Q

what is an angle of repose?

A

the maximum angle at which fragments in a cinder cone will remain stable rather than sliding down the slope

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14
Q

stratovolcano

A

occur when alternating lava flow of lava and pyroclasts build a concave-shaped composite volcano

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15
Q

crater

A

a bowl shaped pit found at the summit of most volcanoes

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16
Q

calderas

A

when a lot of magma leaves the magma chamber, the chamber can’t support the roof so the roof collapses
can form a lake
yellowstone

17
Q

diatreme

A

when breccia fills the vent and channel below it after an explosion

18
Q

fissure eruptions

A

volcanic eruptions that come through vertical cracks in the Earth’s surface

19
Q

flood basalts

A

when successive flows of highly basaltic lava piles up

20
Q

ash-flow deposits

A

sheets of hard volcanic tuffs that come from pyroclast eruptinos

21
Q

at what type of plate boundaries are most volcanoes found?

A

convergent (80%)

22
Q

where do most fissure eruptions occur?

A

along mid-ocean ridges

23
Q

what forms when oceanic crust subducts below continental crust?

A

subduction zone volcanoes form volcanic mountain belts on land such as the Andes

24
Q

what forms when overriding lithosphere is oceanic?

A

subduction zone volcanoes form volcanic island arcs such as the Aleutian Islands

25
intraplate volcanism
volcanoes far from plate boundaries
26
hot spots
intense, localized volcanism far from a plate boundary
27
how are hot spots formed?
hot, solid material rises through narrow jets from deep within the mantle
28
mantle plumes
narrow jets of hot solid material that rise from deep within the mantle
29
volcanic hazards
lahars flank collapse caldera collapse eruption clouds
30
what are lahars and how do they occur?
torrential flow of wet volcanic debris | occur when pyroclastic flows meet a river or snow bank or when a lava flow meets glacial ice
31
flank collapse
the collapse of the side of a volcano occur four times per century if they occur underwater it can cause a tsunami
32
eruption clouds
ash clouds than can damage airplanes
33
how can eruptions be predicted
instruments monitor signals from earthquakes, swelling of the volcano, and gas emissions