3. Types of eruptionChristoph Breitkreuz,

TU Bergakademie Freiberg

Fig. 2.2 Schematic diagram of aexplosive 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 andrelative importance of buoyancy and momentum.Buoyancy carries column to height HB; lateralspreading takes place above HB. Momentum drivessome 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

Bc = distance of“MPS/2“

Fissure eruption

Hawaiian Eruption:- low-viscosity, SiO2-poor magma- Lava fontains- Crater lava lakes- extended lava fields

Strombolian eruption: Etna, Boris Behnke

Southern Vent, 2002

- Medium-viscosity SiO2-poor magma (phenocrysts + microlith!)

Encyclop. Volc 1999

Etna (Photo K. Berg)

Evolution of an intra-plate volcanic field: Springerville Volcanic Field, AZ (Condit & Connor 1996)

Plinian eruption:- high-viscosity magma- volatile-rich- high magma eruption rate(many weeks)

Pinatubo 1991Mt. St. Helens, 1980

Vulcanian eruption: Fossa on Vulcano 1888-90e.g. Santiaguito, Guatemala

J. Lyons, MTU

Soufriere Hills, oct. 1997, p-flow

Typical vulcanian eruptions:- short (< 120 sec.) eruptions (canon shot-like sound)- differentiated magma, moderate volatile content- low magma eruption rate

2002

e.g. Soufriere Hills (Montserrat): 4.8. - 21.10.1997 88 vulcanian eruptions;ballistic bombs (up to 1 m) Up to 1,7 km distance,2/3 p-flows, 1/3 fallout

Druitt et al. 2002

Morrissey & Mastin 1999(Encycl. Volc.)

Transition between vulcanian eruptions and those related to lava dome failure

1966

Phreatomagmatic eruptions:

Surtsey 1963-64

Ukinrek, Alaska, 1977:Maar-forming eruptions(USGS + Lorenz)

Ruhapehu, NZ

Phreatomagmatic eruptions:- Magma – water interaction

(groundwater, ice, lake, sea)- high F, low D, relatively cool- Fragmentation processes:

among others „true“ explosions (according to physical definition) >>>

Leidenfrost film

Physikalisch Vulkanologisches LaborUniversität Würzburg

Spark-flash camera at 0.1 Mframes/sec

Polished steel cylinder, 7.5 cm in diameter at 350 °CWater temperature of 85 °C

vapor film collapse induced by shock-wave passage at stable film boiling conditions

Stable film boiling (1 – 4 mm): reduced heat transfer

Physikalisch Vulkanologisches LaborUniversität Würzburg

Spark-flash camera at 0.1 Mframes/sec

Polished steel cylinder, 7.5 cm in diameter at 350 °CWater temperature of 85 °C

...after about 1.1 ms...

Zimanowski et al. 2004, U Würzburg

Well-known and feared in industrial plants:FCI = Fuel-Coolant-Interaction

Physikalisch Vulkanologisches LaborUniversität Würzburg

HiCam 2, 10 Kframes/secAir gun bullet

Transparent carbonate melt

Physikalisch Vulkanologisches LaborUniversität Würzburg

experiments02

HiCam 2, 10 Kframes/sec

Processes in a surtseyan vent

Another phreatomagmatic process:

Englacial volcanism

2-11-2004Grimsvötn, Iceland

Phreatic activity:

Magma / Lava / or pyroclastic flow deposits provide heat 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).

Water / magma -ratio and type of fragmention