Physical Volcanology. Christoph Breitkreuz, TU Bergakademie Freiberg

Transcription

1 55 Physical Volcanology Christoph Breitkreuz, TU Bergakademie Freiberg

2 Structure: Introduction Reology and deformation of magma and lava Eruption processes and types Volcano forms Emplacement of lava flows, domes and subvolcanic bodies Pyroclastic fragmentation Pyroclasts: Types and classification Pyroclastic transport und deposition Subaquatic and phreatomagmatic processes and resulting textures Cooling textures in SiO 2 -rich (sub-)volcanic bodies Volcanic hazards: Assessment and monitoring exercises: Wednesdays, even weeks, , CVT GP Osteifel: Test

3 Recommended literature BRANNEY, M. & KOKELAAR, P. (2002): Pyroclastic density flows and the sedimentation of ignimbrites.- Geol. Soc. London, Mem., 27, 143 pp. CAS, R.A.F. & WRIGHT, J.V. (1987): Volcanic successions - Modern and ancient.- Allen & Unwin, London, 528S. CHAPIN, C. E. and ELSTON, W. E. (eds.)(1979): Ash-flow tuffs.- Geol. Soc. Amer. Spec. Pap. 180, 211S. CHESTER, D.K., DUNCAN, A.M., GUEST, J.E. & KILBURN, C.R.J. (1985): Mount Etna: Anatomy of a volcano.- Chapman and Hall, London, 404S. DRUITT, T.H. (1999): Santorini volcano.- Geol. Soc. London, Mem. 19, 165 pp. DRUITT, T.H. & KOKELAAR, B.P. (eds.)(2002): The eruption of Soufrière Hills Volcano, Montserrat, from 1995 to Geol. Soc. Mem. 21, 645S. FISHER, R.V. & SCHMINCKE, H.-U. (1984): Pyroclastic rocks.- Springer-Verlag, Berlin, 472S. FISHER, R.V. and SMITH, G.A. (eds.)(1991): Sedimentation in volcanic settings.- Soc. Econ. Paleont. Mineral., Vol. 45. FRANCIS, P. (1993): Volcanoes - A planetary perspective.- Oxford Univ. Press, Oxford, FREUNDT, A. & ROSI, M. (Hrsg.)(1998): From magma to tephra modelling physical processes of explosive volcanic eruptions.- Developments in Volcanol. 4, Elsevier, 318S. GIFKINS, C., HERRMANN, W. & LARGE, R. (2005): Altered Volcanic Rocks: A guide to description and interpretation.- Univ. Tasmania, Centre for Ore Deposits and Exploration Studies, Hobart, 275S. LATTER, J. (ed.)(1989): Volcanic hazards.- Springer, 625S.

4 LIPMAN, P.W. & MULLINEAUX, D.R. (eds.)(1981): The 1980 eruptions of Mount St. Helens, Wash., USA.- U.S. Geol. Surv. Prof. Pap., 1250, ca. 850S. MARTÍ, J. & ERNST, G.G. (eds.)(2005): Volcanoes and the environment.- Cambridge University Press, 471 pp. McCLELLAND, L. et al. (eds.)(1989): Global volcanism, Amer. Geophys. Union, Wash. D.C., 655S. McPHIE, J.M., DOYLE, M. & ALLEN, R. (1993): Volcanic textures - A guide to the interpretation of textures in volcanic rocks.- Univ. Tasmania, Centre for Ore Deposits and Exploration Studies, 1-196, Hobart. ORTON, G.J. (1996): Volcanic environment. - in: READING, H.G. (Hrsg.): Sedimentary Environments: Processes, facies and stratigraphy. - Blackwell Science, Oxford, 3. Aufl., SCHMINCKE, H.-U. (2004): Volcanism.- Springer, Heidelberg, 324 pp. SIGURDSON, H. et al. (eds.)(1999): Encyclopedia of volcanoes.- Academic Press. SIMKIN, T. and FISKE, R.S. (1983): Krakatau The eruption and its effects.- Smithsonian Inst. Press. 464S. THOMPSON, D. (2000): The volcano cowboys - The rocky evolution of a dangerous science.- St. Martin s Press, New York, 326 pp. WHITE, J.D.L., SMELLIE, J.L. & CLAGUE, D.A. (eds.)(2003): Explosive Subaqueous volcanism.- Geophys. Monogr., 140, Journal of Volcanology and Geothermal Research (Elsevier) Bulletin of Volcanology (International Association of Volcanology and Chemistry of the Earths Interior, IAVCEI),

5 Fields of work and position within Geosciences Agriculture Natural Hazards Hydrology Health Petrology Physical volcanology Sedimentology Raw material Mineral deposits e.g. VHMS Engineering Geology

6 Encyclopedia of Volcanoes 1999 Aristotheles Plato A.G. Werner J. Hutton History of volcanology Historic eruptions

7 Santorini, Ägäis 1650 B.C... Forque 1879 Dietrich, ETH Zürich

8 History of volcanology Historic eruptions Encyclopedia of Volcanoes 1999

9 Vesuv 79 A.D. Pompei

10 History of volcanology Historic eruptions Encyclopedia of Volcanoes 1999

11 Krakatau 1883 in Indonesia: Tsunami caused by a shallow marine caldera eruption: fatalities

12 History of volcanology Historic eruptions Encyclopedia of Volcanoes 1999

13 Mt. Pelee, Martinique: St. Pierre Lacroix 1904

14 Lassen Peak, 1915, California

15 History of volcanology Historic eruptions Encyclopedia of Volcanoes 1999

16 Mt. St. Helens, Washington June 1980 Pinatubo 1991

17 Smithsonian Institute Schmincke 1986 Plate tectonics and magma generation Bahlburg & Breitkreuz 2004

18 Geochemical classification Irvine & Baragar 1971

19 Al 2 O 3 content older classifications Required: Norm calculation (e.g. CIPW)

20 Reology and Deformation of Magma and Lava Christoph Breitkreuz, TU Bergakademie Freiberg

21 Glass Mtns, California Mt. St. Helens welded ignimbrite, St. Francis Mtns, Missouri, Proterozoic Sill, Estratos El Bordo, Chile

22 Reology, deformation and fragmentation are controlled by many parameters. The following are important: - Ambient pressure (in the magmatic conduit system, in subaquatic environment) - Viscosity of Magma/Lava - Density of Magma/Lava - Temperature - Deformation rate - Magma ascent rate

23 Just to remember Types of fluids: Newtonian Fluid: water, certain pyroclastic flows Bingham Fluid: (with yield strength) Debris flows, lava / magma certain pyroclastic flows

24 VISCOSITY depends on: Fig. 1.1 Relationship between viscosity and temperature for some magmas. The rhyolite was glassy or liquid through the entire temperature range (From Cas & Wright 1987, after Murase & McBirney 1973). - composition (SiO 2, Al 2 O 3 ) (H 2 O, other volatiles, Na, K etc. ) - temperature - phenocryst content - microlith content, - vesicle content Table 1.1 Estimates of eruption temperatures for some common magmas (After Cas & Wright 1987).

25 H 2 O content and Viscosity: e.g. foaming up of magma during ascent (first boiling) Rhyolite Basalt Fig. 1.2 The effect of H 2 O on the viscosity of (a) granitic and (b) basaltic melts at varying temperatures (From Cas & Wright 1987, after Murase 1962).

26 Fig. 1.3 Densities of some molten volcanic rocks with varying temperature at atmospheric pressure (From Cas & Wright 1987, after Murase & McBirney 1973). Density depends on: composition temperature pressure content of phenocrysts and vesicles

27 Formation of crystals and vesicles depends on: - temperature - presuure - time (Nucleation and diffusion!) T = supercooling (below liquidus) Fig. 1.5 Relation between super cooling ( T) and crystal nucleation and growth rate in a granitic melt (Swanson et al. 1989)

28 (m) FIRST BOILING: - ascent rate - supersaturation (e.g., with respect to H 2 O) Fig. 1.6 Bubble growth and water oversaturation in an ascending rhyolitic magma. The curves define oversaturation in % as a function of the depth in the system during magma ascent. The labels on the curves refer to the ascent or rise rates. The initial conditions are 4 km (a) and 1 km (b), which correspond to initial water concentrations dissolved in the magma of 3.72 and 1.86 wt.%, respectively. Reproduced from Proussevitch and Sahagian (1996) (From Dingwell 1998).

29 Cathodoluminescence image of a quartz phenocryst Embayments in quartz phenocrysts Quartz broken during first boiling Growth zonation Embayments form by: - growth impediment - skeletal growth (quenching)

30 Ignimbrite with crystal fragments

31 Fig. 1.7 Temperature profiles of the Ben Lomond flow at different time steps as derived by numerical modelling with the emplacement temperature of 850 C; Tg = glass transition temperature, FVP = finely vesicular pumice, U.OBS = upper obsidian, TZ = transition zone, RHY = stony rhyolite, L.OBS = lower obsidian, BRX = breccia (from Stevenson et al. 2001) Fig. 1.4 Relation between deformation rate and deformation style of magma or lava depending on temperature; T g = glass transition temperature Land surface T g = glass transition temperature c. 2/3 of the liquidus temperature

32 Panum Crater, Mono Lake, California Glass (above T g ) oozes out of a fracture plain