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Geology > Lecture 6 - Volcanoes/Volcanic Eruptions > Flashcards

Lecture 6 - Volcanoes/Volcanic Eruptions Flashcards

1
Q

What was one of the largest volcanic eruptions in recorded history?

A

Toba

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2
Q

What is the highest volcano

A

Mauna Loa

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3
Q

Global distribution of igneous activity is not random. Most active volcanoes are located within or near ________

A

Ocean basins

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4
Q

There are 4 major types of volcanoes, classified according to

A

their shape, composition of magma and style of eruptions

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5
Q

What are the 3 factors determining the “violence” of a volcanic eruption

A

Composition of magma
Temperature of magma
Dissolved fases in magma

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6
Q

Felsic rocks (granitic, rhyolitic) are sillica rich which will create what type of magma

A

very viscous

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7
Q

Mafic rocks (basaltic) are silica poor, which will create

A

Much more fluid-like magma

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8
Q

low temp = ____ viscosity

A

high

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9
Q

low gas = _____

A

viscosity

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10
Q

if lava is low viscosity, them bubbles can escape. What type of volcano will emerge?

A

non=explosive eruption (effusive

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11
Q

if lava is high viscosity, then pressure inside lava buils up. What type of volcano will emerge?

A

Explosive eruption

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12
Q

what type of lava comes out of an effusive eruption and resembles a twisted/ropey texture

A

pahoehoe lava

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13
Q

what type of lava comes out of an effusive eruption and is rough, jagged blocky texture

A

AA lava

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14
Q

What type of lava comes out of an effusive eruption and is found underwater

A

pillow lava

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15
Q

What is a lava dome/volcanic dome

A

Bulbous mass of congealed lava. Most are associated with explosive eruptions of gas-poor magma

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16
Q

What types of pyroclastic (fire) debris come out of explosive eruption?

A 
tephra: ash and dust
cinders
pumice
lapilli
blocks
bombs
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17
Q

What is tephra?

A

ash and dust (fine glassy fragments)

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18
Q

What is cinders

A

pea-size material

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19
Q

What is pumice

A

porous rock from “frothy lava”

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20
Q

What is lapilli

A

walnut size material

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21
Q

What particles are larger than lapilli

A

blocks and bombs

22
Q

what are blocks

A

hardened or cooled lava (meters)

23
Q

what are bombs

A

ejected as hot lava; teardrop shape

24
Q

What is an eruption column

A

cloud of gas and tephra that can reach 45 km high

25
Q

What is a lateral blast?

A

Build up of pressure and magma/has is directed sideways instead of up . Could also occur if flank collapse exposes magma chamber

26
Q

What happened to mount st helen in 1980s

A

lateral blast

27
Q

what is nuee ardente

A

Fiery pyroclastic flow made of hot gases infused with ash and other debris. glowing avalanche

28
Q

what is the surface source of eruption in a volcano

A

vent

29
Q

what is a volcanic crater/caldera

A

depression surrounding vent

30
Q

whats a fissure on land

A

flood basalt

31
Q

what is a volcanic pipe/neck

A

short conduits that connect a mgma chamber to the surface

32
Q

what’s a lava tube

A

metro system for lava

33
Q

what are the 4 types of volcanoes

A

shield volcano
stratovolcano
cinder cone volcano
lava domes/volcanic domes

34
Q

shielf volcanoes result from

A

effusive eruptions from/near main vent

35
Q

what’s an example of a classic shield volcano

A

mauna loa

36
Q

how much pyroclastic material does a shield volcano produce

A

very litte

37
Q

What type of volcano often produce nuee ardente

A

stratovolcano

38
Q

what volcano produces the most violent eruption

A

stratovolcano

39
Q

where are stratovolcanoes mostly located

A

adjacent to the Pacific Ocean

40
Q

what does stratovolcano result from

A

layered pyroclastic eruptions and very viscous lava flow

41
Q

what type of volcano is associated with explosive eruptions of gas-poor magma

A

lava domes/volcanic domes

42
Q

what is a fumarole

A

vent where gases emerge at the surface of the earth

43
Q

hot springs or thermal springs are areas where hot water comes to the surface of the Earth, usually along _____

A

a fault

44
Q

A geyser results if the hot springs has a plumbing system that allows for accumulation of steam from boiling water. How is it produced

A

When the pressure of steam is higher than the pressure of the water… the steam will move rapidly toward the surface, causing the eruption of the overlying water

45
Q

what are the primary effects of volcanic eruptions

A

lava flows
eruptions/pyroclastic flows
gas emission

46
Q

whats the difference between lava flow and pyroclastic flows

A

lava flow = not explosive, slow moving

pyroclastic flow = fast, hot and potentially widespread

47
Q

What are negative secondary effects of volcanic erruptions

A

lahar, debris avalanches and debris flows, tsunami, flooding, atmospheric efects

48
Q

whats lahar

A

unconsolidated tephra + water = mudflow, rapid down slope movement of material

49
Q

what are positive secondary effects of volcanic erruptions

A

geothermal energy, metallic ore deposits, outgassing of earth (atmosphere), fertile soil (food and drink)

50
Q

what are types of volcanics in terms of volcanic monitoring

A

active, extinct, dormant

51
Q

what is long term forecasting of volcanic monitoring

A

knowledge of geologic and eruption history of the region

52
Q

what are some short term forecasting of volcanic monitoring

A 
seismic monitoring + exploration
ground deformation (tilt meters + GPS)
changes in heat flow
changes in magnetic field
changes in electrical resisitvity 
changes in groundwater system
changes in gas composition

Geology (3 decks)

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