Hazards - volcanoes Flashcards
What is volcanicity?
the process through which either gases and molten rock are either extruded on the earth’s surface or intruded into the earth’s crust
List some volcanic hazards:
- lava flows
- lahars
- tephra
- volcanic/toxic gases
- acid rain
- nuees ardentes/pyroclastic flows
What are lava flows?
flows of lava that can flow quickly or slowly based upon its viscosity
What are lahars?
mudflows, melting ice at high latitudes
What is tephra?
any type of rock ejected by the volcano
What are volcanic/toxic gaes?
released during some eruptions, can replace oxygen as it is heavier
What is acid rain?
caused when gases such as sulfur dioxide are released into the atmosphere
What are pyroclastic flows?
clouds of hot burning ash/gas that collapses down a volcano at high speeds
List the 3 magma types:
- basalitic
- andesitic
- rhyolitic
Characteristics of basalitic magma:
- 1100 degrees celcius
- low gas content
- low viscosity
- 50% SiO2 content
Characteristics of andesitic magma:
- 1000 degrees celcius
- moderate gas content
- moderate viscosity
- 60% SiO2 content
Characteristics of rhyolitic magma:
- 800 degrees celcius
- high gas content
- high viscosity
- 70% SiO2 content
What are hotspots?
areas of volcanic activity that are not related to plate boundaries. Hot magma plumes from the mantle rise and burn through weaker points of the crust. The plume stays in place but the plates continue to move
Example of a hotspot:
Hawaiian Islands
Where are volcanoes located?
(usually) along destructive and/or constructive plate margins or on hotspots
How is the magnitude of volcanoes measured?
by the VEI (Volcanic Explosivity Index)
What does it mean if a volcano is more explosive?
more powerful / higher magnitude
What does it mean if a volcano is more effusive?
less powerful / lower magnitude
What is an active volcano?
a volcano that had erupted in living memory (150-200yrs)
Example of an active volcano?
Etna
What is a dormant volcano?
a volcano that has erupted in historical record (500 yrs)
Example of a dormant volcano:
Helenus
What is an extinct volcano?
a volcano which will not erupt again (10,000 years)
Example of an extinct volcano?
Edinburgh Castle
