Volcanoes Flashcards
what are the four steps in the management of tectonic hazards?
prediction, monitoring, protection and planning
how can volcanic activity be predicted?
measuring seismic activity, ground deformation using tiltometres, upward movement of iron-rich magma using magnetometres, rising groundwater temperature and/or gases, warning signs such as small eruptions
examples of primary hazards caused by volcanoes
tephra, pyroclastic flows (nuees ardentes), volcanic gases, pyroclastic fallout, lava flows
what is tephra?
solid material of varying grain size ranging from volcanic rocks to ash
what are pyroclastic flows?
very hot (over 800’) mixture of super-heated gas, ash and volcanic rock that flows down the sides of a volcano
what are volcanic gases?
these include carbon dioxide, carbon monoxide, hydrogen sulphide, sulfur dioxide and chlorine
examples of secondary hazards caused by volcanoes
lahars, flooding, tsunamis, acid rain and climate change
what are lahars?
melted snow and ice combined with volcanic ash which can flow very quickly and can travel for tens of kilometres
what happens at constructive margins?
basaltic lava is formed here, it is very hot and has a low viscosity, the eruptions are frequent but not very violent
what happens at destructive margins?
andesitic and rhyolitic lava are formed here, they are cooler and more viscous, they usually erupt intermittently but are short-lived
what are the two types of volcanoes?
stratocone and shield
what type of lava do stratocones have?
it has a-ah (blocky) lava
what type of lava do shields have?
it has pahoehoe lava
what are the different types of volcano?
icelandic, hawaiian, vulcanian, vesuvian, peleean and plunian
describe basic shield volcanoes
they are shallow-sided and are formed by pure basalt that cools as it comes down from the summit.
