Volcanism - lecture 2 Flashcards
the form of a volcano is directly linked to what?
its location
high viscosity speed?
slow flowing and quick to solidify
where do non-explosive basaltic lava flows and shields occur where?
at constructive margins and oceanic hot spots
where do stratovolcanoes and calderas occur?
at destructive plates and continental hot spots
what is a stratovolcano?
a volcano built up of alternate layers of lava and ash
what is a caldera?
a large volcanic crater, especially one formed by a major eruption leading to the collapse of the mouth of the volcano
what is basaltic lava also referred to as?
mafic lava
what are the 2 types of basaltic lava?
1 - Aa = rough surface
2 - pahoehoe = smooth or ropy
andesitic and rhyolitic volcanoes occur predominantly where?
the pacific ring of fire
what are the 3 ways that earth loses heat?
1 - conduction - through crust
2 - plate tectonic convection - cycle of material from interior to surface
3 - convection: mantle plumes rise from core-mantle boundary = hot spot for volcanoes
3 main heat sources of earth?
1 - accretion from protoplanetary disk
2 - tidal forcing on solid earth
3 - mostly decay of radioactive species in earth
what does the % silicate in the magma determine?
rheology e.g. viscosity
how do silicate tetrahedra impede gas release?
they form lattices
what is a pyroclastic flow?
a dense, destructive mass of very hot ash, lava and gas ejected explosively from a volcano flowing at great speed
overview of basaltic activity:
- gases move independently of the melt
- gas rises faster = degassed lava flows
- range of bubble morphologies
