Physical Geography - Hazards - Volcanoes Flashcards
Name the two types of volcanoes.
Composite
Shield
Where are composite volcanoes formed?
At both oceanic to oceanic convergence plate margins.
And oceanic to continental convergence plate margins
Where are shield volcanoes formed?
At oceanic - oceanic divergent plate margins as well as hotspots.
What are the two types of lava?
Which type of volcano erupts this type of lava?
Basaltic lava (Shield Volcanoes)
Andesitic lava (Composite Volcanoes)
Describe the characteristics of Basaltic lava.
There are 7
Low viscosity (stickiness)
1200 Degrees Celsius
Runny and water like
Lower silica content
Long time to cool and solidify, so flows long distances
Eruptions are frequent, but are relatively gentle
Lava and steam ejected
Describe the characteristics of Andesitic lava.
There are 7
Viscous (Sticky)
800 Degrees Celsius
Flows more slowly and shorter distances
Higher silica content
Cools and solidifies faster, so flows short distances
Eruptions are less frequent but are violent due to build up of gasses
Ash, ricks, steam and lava are ejected.
What is tephra?
Solid matter ejected by a volcano into the air.
It ranges in size from bombs to ash.
What are tephra’s impacts?
Loss to agricultural land.
Carrying of noxious gasses, acids, salts and heat.
Tephra can change rainfall/runoff relation.
What is pyroclastic flow?
Fast flowing movements of hot gas and volcanic debris.
Reach top speeds of 430mph and temperatures of 1000 Degrees Celsius.
What are pyroclastic flow’s impacts?
Asphyxiation (Deprivation of oxygen)
Burial/Crushing.
Widespread damage to infrastructure.
What is Nuees Ardents?
A dense cloud of hot ash and gas.
Moves rapidly.
A glowing cloud.
What are Nuees Ardents impacts?
High temperatures
Toxic gasses
What is a lahar?
A flow of wet material (ash, debris, mud and water)
Viscous, consistency of wet concrete.
Forms by hot pyroclastic flow entering watershed systems.
Can move up to 40 m/s for 300km.
What is a volcanic gas?
Magma containing dissolved gases.
Water vapor is released mostly, but Carbon dioxide, Carbon monoxide, sulfur oxide and fluorine are released also.
What are the impacts of volcanic gases?
Reacting with water forming acids, acids destroy vegetation.
Atmospheric veils of dust effect climate.
What is acid rain?
Volcanic acid rain is typically dominated by hydrochloric acid and sulfuric acid arising from plume gases.
What are the impacts of volcanic gases?
Mixing with water, becoming toxic.
Damages forests - Can’t use its essential nutrients.
Damages and kills crops.
