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Earth Science > Volcanoes > Flashcards

Volcanoes Flashcards

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1
Q

Molten rock beneath the Earth’s surface

A

Magma

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2
Q

Erupted magma

A

Lava

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3
Q
  • igneous rocks contain a high percentage of dark silicate minerals and calcium-rich plagioclase feldspar (but no quartz) and tend to be dark in color
A

Basaltic

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4
Q

Contains mainly light-colored silicate minerals - quartz and potassium feldspar

A

Rhyolite

Intrusive equivalent: granite

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5
Q

Have a composition between basaltic and rhyolitic rocks

A

Andesitic rocks

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6
Q

Basaltic or

A

Mafic

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7
Q

Rhyolitic or

A

Felsic

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8
Q

Basaltic * magmas contain … SiO2

  • gas content
  • eruptive temperature
  • viscosity
A

Least ~ 50% SiO2
Least ~ 0.5-2.0% Gas
Highest Temperature (1000-1250 C)
Least viscous

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9
Q

Rhyolitic * magmas contain … SiO2

  • gas content
  • eruptive temperature
  • viscosity
A

Most ~ 70% SiO2
Most ~ 5-8%
Lowest Temperature (650-900 C)
Most Viscous

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10
Q

Basaltic (mafic)

A

High in Mg, Ca, Fe

Low in Na, K

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11
Q

Rhyolitic (felsic)

A

High in Na, K

Low in Mg, Ca, Fe

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12
Q

The magmas generated by melting mantle rocks tend to have * composition

/partial melting of solid rock/

A

Basaltic

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13
Q

In continental crust, the rising molten rock ponds at the crust-mantle boundary, melting the overlying crustal rock. This generates * magna of * composition

A

Less dense, more silica-rich magma

Andesitic or rhyolitic composition

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14
Q

Nonexplosive eruptions that produce outpourings of fluid lava

A

Quiescent or efusive

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15
Q

Opposite of effusive eruptions

A

Explosive eruptions

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16
Q

Two primary factors that determine how magma erupts:

A

Viscosity and gas content

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17
Q

What type of magma tends to generate quiescent (nonexplosive) eruptions?

A

Basaltic: fluid + low gas content

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18
Q

What type of magma tends to generate explosive eruptions?

A

Rhyolitic and andesitic

Silica-rich magmas, most viscous, greatest amount of gases

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19
Q

Magma’s viscosity depends on

A

Temperature and silica content

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20
Q

Viscous

  • SiO2
  • C
A

More silica, more viscous

Lower temperature, more viscous

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21
Q

Most abundant gas found in most magma

A

Water vapor

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22
Q

Vast majority of Earth’s lava is

> 90%

A

Basaltic

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23
Q

Two types of lava

A

Aa

Pahoehoe

24
Q

Have surfaces of rough jagged blocks with dangerously sharp edges

A

Aa flows

25
Q

Exhibit smooth surfaces that sometimes resemble twisted braids of ropes

On which one can walk

A

Pahoehoe

26
Q

Dissolved gases held in molten rock by confining pressure

A

Volatiled

27
Q

Most abundant-least abundant gas released in the atmosphere

A

Water vapor (H2O), CO2, SO2

H2S, CO, H2

28
Q

When volcanoes erupt, they eject pulverized rock and fragments of lava and glass called

A

Pyroclastic materials

29
Q

Pyroclastic materials

Etymology; also known as

A

Pyro = fire, clast = fragment

Tephra

30
Q

Produced when gas-rich viscous magma erupts explosively

Less than 2mm (0.08 in)

A

Ash and dust particles

31
Q

“Little stones”

Small beads to walnuts (2-64 mm)

A

Lapilli or cinders

32
Q

Larger than 64 mm or 2.5 in

*hardened, incandescent

A

Blocks - hardened lava

Bombs - incandescent lava

33
Q

Vesicular ejecta produced most often during eruption of basaltic magmas

Reddish-brown fragments

A

Scoria

34
Q

Usually light color and less dense emitted when magmas with an andesitic or rhyolitic compositions erupt explosively

A

Pumice

35
Q

Volcanic activity frequently begins when a * develops in Earth’s crust as magma moves forcefully toward the surface

A

Fissure (crack)

36
Q

Path of magma localized into somewhat pipe-shaped * that terminates at a surface opening called *

A

Conduit, vent

37
Q

Coneshaped structure created by successive eruptions of lava, tephra

A

Volcanic cone

38
Q

Located at the summit of most volcanic cones is a funnel-shaped depression

A

Crater

39
Q

Very large circular depressions

> 1 km, at most 50 km

|<1 km|•

A

Calderas

Collapse pits or craters

40
Q

Vent that emits only gases

A

Fumaroles (fumus = smoke)

41
Q

Produced by accumulation of fluid basaltic lavas

Huge, gently sloping volcanoes built of very thin lava spreading out in all directions from a central vent

Broad, slightly dome structure *oceanic

A

Shield volcanoes

42
Q

Result from eruptions of moslty small pieces of scoria and pyroclastics *basaltic

A

Cinder cones/ scoria cones

43
Q

Cone-shaped volcanoes composed of layers of lava, ash and rock debris

A

Composite cone volcanoes “stratovolcanoes”

44
Q

Built by slow eruptions of highly viscous lava. Any steep-sided mound formed when lava reaching The Earth’s surface is so viscous that it cannot flow away readily and accumulated around the vent

A

Lava domes

45
Q

A fluidized mixture of hot rock fragments, hot gases infused with incandescent ash and larger lava fragments

Also called

A

Pyroclastic flows

Nuee ardentes (glowing avalanches)

46
Q

The greatest volume of volcanic material is extruded from *

These voluminous accumulations are * because they tend to be rather flat and broad

A

Fissures

Basalt plateaus

47
Q

Volcanic object created when magma hardens within a vent on an active volcano

A

Volcanic plug, volcanic neck or lava neck

48
Q

Body of intrusive igneous rock that is crystallized from magma slowly cooling below the surface of the Earth

A

Pluton

49
Q

Intrusive igneous bodies are generally classified according to their shape as either * or * (large and blob shaped)

A

Tabular (tabula = table), massive

50
Q

Orientation: * if they cut across existing structures

  • if they intrude parallel to features such as sedimentary strata
A

Discordant, concordant

51
Q

Discordant bodies that serve as tabular conduits that transport magma toward Earth’s surface

A

Dikes

52
Q

Concordant bodies that tend to accumulate magma and gradually increase in thickness

A

Sills

53
Q

Large mass of intrusive igneous rock that forms from cooled magma

> 100 km2

A

Batholith

54
Q

Smaller plutons

A

Stocks

55
Q

Igneous intrusion that has split apart two strata, resulting in a domelike structure

Concordant pluton that has been injected between two layers of sedimentary rock

A

Laccolith

56
Q

Plate motions provide the mechanisms by which mantle rocks undergo partial melting to generate magma. As hot rock rises, it experiences a decrease in confining pressure and mag undergo *

A

Decompression melting

57
Q

the process which involves movements of the earth’s crust such that a portion id pushed up, push down or forced sideways

A

DIASTROPHISM

Earth Science (9 decks)

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