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Ash Flow TuffsAsh Flow Tuffs
References:Smith, RL, 1960, As flows. Geol. Soc.
America Bull., 71:795-842.Sparks, RSJ, 1976, Grain size variations in
ignimbrites and implications for the transport of pyroclastic flows: Sedimentology, 23:147-188.
Encyclopedia of Volcanoes, pp. 581-599
MorphologyMorphology
• Controlled by topography• Fill depressions• Even upper surface• Valley ponded deposits• Veneer deposits• Multiple lobes and fans• Lateral levees
Pyroclastic Flows of 472 AD, Vesuvius
Standard Section (Sparks, 1976)Standard Section (Sparks, 1976)
• Layer 1 (ground layer or surge)
• Layer 2 (flow unit)
• Layer 2a (fine-grained basal)
• Layer 2b (main body of flow)
• Layer 3 (ash cloud)
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Base of Bandelier TuffBase of Bandelier TuffGas PipeGas Pipe
Honeycomb Hills, UtahHoneycomb Hills, Utah Komagatake Tuff, JapanKomagatake Tuff, Japan
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AshAsh--flow Sheets, Smith (1960)flow Sheets, Smith (1960)
• Flow units
• Cooling units
• Welded tuffs
• Compound cooling units
Teepees, Bandelier TuffTeepees, Bandelier Tuff