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HAZARDS > Volcanic Hazards > Flashcards

Volcanic Hazards Flashcards

1
Q

What is lava?

A

Molten rock above the surface

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1
Q

What is magma?

A

Molten rock below the surface

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2
Q

What differs in lava?

A

Viscosity

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3
Q

What is viscosity?

A

How thick the lava is

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4
Q

What 2 things control viscosity of lava/magma?

A

Temperature
Composition of magma

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5
Q

What is the viscosity of the lava at constructive boundaries?

A

High temperature
Low silica content

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6
Q

What is the viscosity of the lava of destructive boundaries?

A

Lower temperature
High silica content

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7
Q

What are effusive eruptions?

A

Where lava pours out of a volcano freely

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8
Q

When do effusive eruptions occur?

A

When the lava is low viscosity

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9
Q

What type of lava is at effusive eruptions?

A

Basaltic

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10
Q

Where are effusive eruptions found at?

A

Constructive plate margins

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11
Q

What are explosive eruptions?

A

Where lava doesn’t escape easily and volcano explodes

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12
Q

When do explosive eruptions occur?

A

Where lava is viscous and doesn’t flow freely

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13
Q

What type of lava is at explosive eruptions?

A

Andesitic

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14
Q

Where are explosive eruptions found at?

A

Destructive plate margins

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15
Q

What is basalt lava?

A

Lowest silica content
Low viscosity
Flows a long distance
Associated with effusive eruptions

16
Q

What is andesite lava?

A

Higher silica content
Higher viscosity
Flows a shorter distance
Associated with explosive eruptions

17
Q

What is rhyolite lava?

A

Highest silica content
Higher viscosity
Doesn’t flow far at all
Associated with explosive eruptions

18
Q

Why do lavas behave differently?

A

Due to composition and viscosities

19
Q

What is tephra?

A

Solid material that varies in size from volcanic bombs to ash

20
Q

Why are low viscosity lavas not hazardous?

A

Can flow for long distances but tend to be slower so not hazardous

21
Q

Why are pyroclastic flows hazardous?

A

Very hot and one of the deadliest hazards of volcanoes

22
Q

What are pyroclastic flows?

A

A mix of gas and tephra - very hot and moves at speeds up to 700km an hour

23
Q

Why are volcanic gases hazardous?

A

C02, chlorine, Carbon monoxide and sulphur dioxide plus fluorine are all present

24
Q

What are lahars?

A

Unconsolidated ash from a recent eruption combined with water which may have be swept down river valleys in the form of a hot,dense,fast-flowing mudflow.

25
Q

What does lahars form?

A

A debris flow composed of water, ash and rocks

26
Q

How is climate change hazardous?

A

Gases have a large effect on climate

27
Q

What is VEI?

A

Volcanic Explosively Index

HAZARDS (6 decks)

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