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Hazardous earths > volcanoes > Flashcards

volcanoes Flashcards

1
Q

Where are volcanoes located?

A

Along tectonic boundaries and appear in long chains

Destructive and construction boundaries

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2
Q

Give an example of is chain of volcanoes

A

The Pacific ring of fire

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3
Q

What is the difference between lava and magma?

A

Lava is magma above the surface and magma is molten rock beneath the surface

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4
Q

What is viscosity?

A

It is the stickiness of the lava or its resistance to flow

The more silica the more resistant the lava is

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5
Q

What is a active volcano, a dormant volcano and an extinct volcano?

A

Active- erupted recently and frequently

Dormant- has erupted in the last 2000 years but not recently

Extinct- is unlikely to erupt ever again and is dead or extinct

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6
Q

What are the three types of lava?

A

Basaltic
Andesitic
Rhyolitic

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7
Q

What is a crater?

A

The basin shaped depression in the top of a volcano where material is ejected

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8
Q

What is a volcanic bomb?

A

Semi molten pieces of rock ejected from a volcanic vent

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9
Q

What is a secondary cone?

A

When there is great pressure inside a volcano and the vent or crater is blocked magma is forced to the surface by a different route

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10
Q

What is a magma chamber?

A

Where all the molten rock that comes out of the volcano is stored underground

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11
Q

What is the vent?

A

The Lin shaft that feeds magma from the magma chamber to the crater

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12
Q

What are the two types of volcanic landforms?

A

Extrusive and intrusive

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13
Q

What are extrusive landforms?

A 
Molten rock reaching the surface can create these landforms;
Shield
Composite
Fissure
Acid dome
Calderas
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14
Q

What are intrusive landforms?

A

Molten rock that are injected into the crust also create landforms that my not be seen in the surface
As magma cools slowly crystals are formed in rock
Batholiths are often done-shaped and exposed later due to erosion

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15
Q

What are the properties of rhyolitic lava?

A

Acid up to 75% SiO2
Very viscous up to 10^6 x that of basalt
Rarely forms flows, mainly domes and spires
Traps gas builds up pressure and explosively erupts so effects can be catastrophic

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16
Q

What are the priorities of andesitic lave?

A

Intermediate c. 65% SiO2
Considerably more viscous than basalt, up to 10^3 x basalt
Thicker so less extensive flows

17
Q

What are the priories of basaltic lava?

A

C. 45% SiO2

  • the least viscous of lava flows
  • forms thin laterally extensive flows which are confined by topography
18
Q

What are the 5 types of volcano?

A 
Shield
Acid dome
Cinder cone
Composite cone/ strato
Caldera
19
Q

What are the features of a shield volcano?

A
  • constructive boundaries and hotspots
  • low with gently sloping sides
  • wide base
  • eruptions aw frequent and non violent
  • thin runny lava to travels far from vent, fast flowing with high silica content
20
Q

What are the feature of acid dome and cinder cone volcanos?

A
  • simplest form of volcano
  • built from particles and blobs of lava
  • has charged violent eruptions
  • steep sided with a bowl shaped crater
  • most are less than 1000 ft
  • thick lave so can’t travel far
21
Q

What are the features of a composite/ stratovolcano?

A
  • destructive boundaries
  • composed of alternating layers of ash and acid lava
  • steep sided and symmetrical
  • high with narrow base
  • very explosive eruptions with pyroclastic flows
  • explosive as lave cools in vent
  • acid lava, very thick low silica content
22
Q

What are fissure eruptions?

A

A fissure is a elongated fracture or crack at the surface from which lava erupts

  • explosions typically dwindle to a central vent after a period of hours
  • lava flow can flow back into the ground by luring into a crack or an open erupting fissure
23
Q

What are the 7 types o eruptions?

A
  • Icelandic
  • Hawaiian
  • Strombolian
  • Vulcanian
  • Vesuvian
  • peléean
  • Plinian
24
Q

What are the properties of Icelandic eruptions?

A

Basaltic lava

Lava flows gently from fissures

25
Q

What are the properties of Hawaiian eruptions?

A

Basaltic lava

Lava flows gently from central vent

Hazardous earths (4 decks)

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