Flashcards in Primary Volcanic Hazards Deck (17):
Very small solid particles ejected from a volcano during an eruption.
Define Lava Flow.
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.
Define Nuees Ardentes.
Highly destructive, fast moving incandescent mass of gas.
Similar to pyroclaustic flows.
Define Pyroclasutic Flows.
Dense, destructive mass of very hot (over 800') ash from a volcano, flowing up to 700 km per hour.
Solid matter such as dust, ash and cinders ejected into air. Size of particles that erupt nearer volcano are largest, smaller further away.
Define volcanic gases.
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.
Hazards/damage from Ash.
Hazards/damage from Lava Flows.
Everything in pathway ignited.
Hazards/damage from Nuees Ardentes.
Dangerous due to speed, temperature and tendency to travel near ground - engulfment of everything in pathway.
Hazards/damage from Pyroclasutic Flows.
Extreme temperatures ignite everything, melt snow.
Hazards/damage from Tephra.
Burns and irritation from acids inside it.
Disruption to telephone communications/flights/vegetation.
Hazards/damage from Volcanic Gases.
Directly harmful to humans, animals, plants.
CO2, carbon monoxide emitted.
Other dangerous gases causing skin irritation.
Example of a volcano which produced Ash.
Huge amounts deposited on flanks of volcano. Vegetation killed from ash.
Example of a volcano which produced Lava Flows.
Less viscous with high alkaline composition, fed by plume under volcano - very fluid - 97km per hour.
Example of a volcano which produced Pyroclaustic Flows.
Mt St Helens.
The erupted 8km (5miles) from vent.
17 pyroclaustic flows occurred may 18th.
Example of a volcano which produced Tephra.
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.