Primary Volcanic Hazards

Question 1

Define Ash.

Answer 1

Very small solid particles ejected from a volcano during an eruption.

Question 2

Define Lava Flow.

Answer 2

Streams of molten rock that pour or ooze from an erupting vent. The speed of lava flow depends on type of lava, viscosity, steepness of ground and weather it flows down a broadsheet or fine channel.

Question 3

Define Nuees Ardentes.

Answer 3

Highly destructive, fast moving incandescent mass of gas.

Similar to pyroclaustic flows.

Question 4

Define Pyroclasutic Flows.

Answer 4

Dense, destructive mass of very hot (over 800’) ash from a volcano, flowing up to 700 km per hour.

Question 5

Define Tephra

Answer 5

Solid matter such as dust, ash and cinders ejected into air. Size of particles that erupt nearer volcano are largest, smaller further away.

Question 6

Define volcanic gases.

Answer 6

Given off by active volcanoes.
Including gases trapped in cavities in volcanic rock, dissolved gases in magma/lava.
eg carbon dioxide/monoxide, hydrogen sulphide, chlorine.

Question 7

Hazards/damage from Ash.

Answer 7

Respiratory effects.
Eye symptoms.
Skin irritation.

Question 8

Hazards/damage from Lava Flows.

Answer 8

Everything in pathway ignited.

Question 9

Hazards/damage from Nuees Ardentes.

Answer 9

Dangerous due to speed, temperature and tendency to travel near ground - engulfment of everything in pathway.
Burns.

Question 10

Hazards/damage from Pyroclasutic Flows.

Answer 10

Extreme temperatures ignite everything, melt snow.

Destroy farmland/forest/buildings.

Question 11

Hazards/damage from Tephra.

Answer 11

Burns and irritation from acids inside it.

Disruption to telephone communications/flights/vegetation.

Question 12

Hazards/damage from Volcanic Gases.

Answer 12

Directly harmful to humans, animals, plants.
CO2, carbon monoxide emitted.
Other dangerous gases causing skin irritation.

Question 13

Example of a volcano which produced Ash.

Answer 13

Montserrat.

Huge amounts deposited on flanks of volcano. Vegetation killed from ash.

Question 14

Example of a volcano which produced Lava Flows.

Answer 14

Nyiragongo.

Less viscous with high alkaline composition, fed by plume under volcano - very fluid - 97km per hour.

Question 15

Example of a volcano which produced Pyroclaustic Flows.

Answer 15

Mt St Helens.
The erupted 8km (5miles) from vent.
17 pyroclaustic flows occurred may 18th.

Question 16

Example of a volcano which produced Tephra.

Answer 16

Mt St Helens.

It covered the town of Yakma, causing a dark sky during the middle of the day. Ash fell over 22,000 square miles.

Question 17

Example of a volcano which produced Volcanic Gases.

Answer 17

Mt Pinatubo.

1991 eruption injected more than 250 megatons of gas on a single day.