Volcanology Part 2 (Volcanic Products, Volcanic Hazards, Volcanology of the PH) Flashcards
Volcanic Products
Lava Flow
Pyroclastic materials
Glass
Pyroclastic density currents (PDCs)
Streams of lava pouring from a fissure or a vent during an eruption which have different forms due to the different composition and environment of deposition.
Lava Flow
is a type of lava flow characterized by its rough, jagged surface that have spiky and sharp edges, and are often associated with fluid basaltic flows.
‘A’a flow
is a type of lava flow that form relatively smooth surfaces that often resembles twisted ropes and are often products of basaltic flows.
Pahoehoe flow
Short, detached, vesicle-free, proximal lava that are often produced by viscous lava, such as andesitic and rhyolitic lava.
Block lava
Lava flows that formed as structures composed of numerous smooth, tube-like protuberances, which are good indicators for the surrounding environment as they form underwater.
Pillow lava
Volcanic material of varying sizes produced from volcanic eruptions
Pyroclastic Materials
Pyroclastic material ejected into the atmosphere
Tephra
Solid ejecta with sizes greater than 64 mm.
Block
Pyroclastic material ejected into the atmosphere
Bomb
A fractured surface texture formed when bombs cool.
Breadcrust texture
Rock fragments with grain sizes ranging from 2-64 mm formed from droplets of lava.
Lapilli
Tephra that is usually glass, having grain sizes lesser than 2 mm.
Ash
Lapilli-sized pyroclastic deposits that are good indicators for environment during deposition as they formed due to saturation from water.
Accretionary Lapilli
Naturally occurring solids that lacks an orderly crystalline structure, which formed due to quenching or rapid cooling of lava.
Glass
Black, glassy, streamlined particles that formed as lava droplets that quenched in flight.
Pele’s tears
Golden, acicular, glassy strands that formed as lava droplets were propelled through the air, being partially stretched into shape.
Pele’s hair
Generally hot flows made up of a mixture of pyroclastic materials and hot gases that can travel at rapid speeds.
Pyroclastic Density Currents (PDCs)
A blanket of pyroclastic material and tephra that fall to the ground due to gravity, which is identified to have a good sorting of angular juvenile clasts.
Pyroclastic Fall
A dense, “ground- hugging” flow of pyroclastic materials that moves at speeds up to 150 km/h that can reach over to a 1000 °C and develop poorly sorted beds with rounded clasts that can produce block-and-ash flows.
Pyroclastic Flow
A more dilute and mobile current which have low concentrations of particles mixed with gases that can travel up hills and valleys at high velocity and horizontally from the eruption site.
Pyroclastic Surge
Siliceous, low to moderate density, hot vesiculated flows.
Pumice flows
Andesitic to basaltic, hot vesiculated flows
Scoria flows
Compacted or “welded” pumice and tuff.
Ignimbrite
Flattened or compacted pumice in ignimbrites.
Fiamme
French for “fiery clouds,” are fluidized mixtures of hot, incandescent rock fragments and gases that flow along the surface as a “glowing avalanche” of pyroclastic debris.
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