3. Types of eruption Christoph Breitkreuz, TU Bergakademie Freiberg Fig. 2.2 Schematic diagram of a explosive volcanic system showing different regions and rheological regimes from non-vesiculated magma to eruption plume. (From Fisher & Schminke 1984, after Wilson et al., 1980). Fig. 2.4 A schematic volcanic eruption column, showing the variation of velocity with height and relative importance of buoyancy and momentum. Buoyancy carries column to height HB; lateral spreading takes place above HB. Momentum drives some material upwards to a maximum height HT (Orton 1996, from Self & Walker, 1994). Magmatic fragmentation: by expansion of vesicles and high deformation rate Magmatic- phreatomagmatic- phreatic after Walker 1973 after Pyle 1989 B c = distance of“MPS/2“
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3. Types of eruption - TU Bergakademie Freiberg€¦ · 3. Types of eruption Christoph Breitkreuz, TU Bergakademie Freiberg Fig. 2.2 Schematic diagram of a explosive volcanic system
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3. Types of eruptionChristoph Breitkreuz,
TU Bergakademie Freiberg
Fig. 2.2 Schematic diagram of a explosive volcanic system showingdifferent regions and rheologicalregimes from non-vesiculated magmato eruption plume. (From Fisher & Schminke 1984, after Wilson et al., 1980).
Fig. 2.4 A schematic volcanic eruption column, showing the variation of velocity with height and relative importance of buoyancy and momentum. Buoyancy carries column to height HB; lateral spreading takes place above HB. Momentum drivessome material upwards to a maximum height HT(Orton 1996, from Self & Walker, 1994).
Magmatic fragmentation: byexpansion of vesicles and high deformation rate
Magma / Lava / or pyroclastic flowdeposits provideheat for phreatic eruptions
Prior to the large eruption of May, 18th, 1980:Rising magma caused boiling and phreatic eruption of groundwater:
(USGS)Mt. St. Helens
Fig. 2.6 Interrelations of explosive energy, water-magma ratio, style of volcanic activity and volcaniclastic fragments in basaltichydrovolcanic eruptions (largely after Wohletz & Sheridan, 1983). The smallest fragments are produced in Taalian eruptions whenmost thermal energy is transferred to mechanical energy. The shape of shards produced (1-5) depends on the viscosity of the magmaand its degree of vesiculation: blocky shards (1) of poorly vesicular magma are most common; irregular, globular and spherical shards(2-4) indicate fluidal melts; platy and cuspate shards are part of vesicle walls and develop if vesiculated, generally more viscous magmainteracts with water. Non-explosive quench fragmentation can occur in any environment. For instance, views of hyaloclastites are fromthe Mid-Atlantic ridge (Schmincke et al., 1978) and a Permian example where lava flowed over unconsolidated nearshore marinesediments (From Orton 1996).