Lava Domes 29 March 2019

1. Lava Domes 29 March 2019

2. Importance of lava domes Lava domes really can be considered as “corks” in a champagne bottle…the analogy is a good one It is RARE to see no explosive activity associated with lava domes Lava domes are important in terms of TRANSITIONS between effusive and explosive activity

3. STRUCTURE OF THE LECTURE • 1. Morphology • Repeating signals and the • effusive-explosive transition • 3. Some general laws

4. Growth rates of lava domes

5. Lava dome advection and solidification times tS = solidification time tA = advection time Dimensionless number B : Fink JH, Griffiths RW (1998) J Geophys Res 103:527-545

6. Lava dome morphology Fink JH, Griffiths RW (1998) J Geophys Res 103:527-545

7. Side views of the four analogue domes from the previous page Fink JH, Griffiths RW (1998) J Geophys Res 103:527-545

8. Lava dome advection and solidification times tS = solidification time tA = advection time Dimensionless number B : Fink JH, Griffiths RW (1998) J Geophys Res 103:527-545

9. Unzen lava dome, late May 1991

10. Soufrière St. Vincent lava dome, 1979

11. Early Mt. St. Helens lava dome, 1980

12. Venusian “pancake” domes

13. 1. Morphology 2. Repeating signals and the effusive-explosive transition 3. Some general laws

14. Volcano seismicity (“VT event”) [or long period earthquake (“lp event”)] courtesy USGS

15. Mt. St. Helens (USA)

16. 2004-2008 lava dome 18 May 1980 collapse amphitheatre vent area glacier vent Thermal infrared image 1980’s lava dome glacier Iverson et al. (2006) Nature 444:439-443

17. Lava dome evolution, 2004-2005 (about 0.072 km3 extruded in ~15 months) Iverson et al. (2006) Nature 444:439-443

18. Seismogram of the dome, 1 Dec 2005 Iverson et al. (2006) Nature 444:439-443

19. Stick-slip model of dome extrusion Iverson et al. (2006) Nature 444:439-443

20. Soufrière Hills (Montserrat)

22. Lava dome behaviour, May 1997 Significant lava dome collapses and pyroclastic flows (block and ash flows) associated with these peaks in activity Voight et al. (1999) Science 283:1138-1142

23. Block and ash flow deposits (Merapi, Indonesia) lava dome fragment

24. Lava dome growth, 2002-2003

26. Largest dome collapse at Montserrat: July 2003 collapse peak at 0335 hours local time Herd et al. (2005) J Volcanol Geotherm Res 148:234-252

27. Vulcanian explosions associated with the dome collapse Herd et al. (2005) J Volcanol Geotherm Res 148:234-252

28. Vulcanian eruptions SO2 gas release (no solid material) SPACING COLUMN HEIGHT

29. Galeras (Colombia)

32. Summer 1992

33. Long period seismic signals associated with dome destruction and vulcanian eruptions at Galeras (“tornillos”) These events are a manifestation of pressurization within the shallow plumbing system of the volcano Narváez M L et al. (1997) J Volcanol Geotherm Res 77:159-171

34. Tornillos with slowly decaying coda Narváez M L et al. (1997) J Volcanol Geotherm Res 77:159-171

35. Remarkable tornillo signals Narváez M L et al. (1997) J Volcanol Geotherm Res 77:159-171

36. Key changes before vulcanian eruptions at Galeras 14 January 1993 eruption 23 March 1993 eruption 7 June 1993 eruption The “h” term in (c ) is a damping coefficient…low values correspond to gradually decaying tornillos, while higher values correspond to a more rapidly decaying tornillo Gómez M DM, Torres C RA (1997) J Volcanol Geotherm Res 77:173-193

37. 1. Morphology • 2. Repeating signals and the effusive-explosive transition • 3. Some general laws

38. The fragmentation threshold Spieler et al. (2004) Earth Planet Sci Lett 226:139-148

39. Viscous behaviour of fluids Courtesy Wikipedia

40. Lava dome rheology Shear-thinning behaviour Note the alignment and breakage of crystals • log  = -0.993 + (8974 / T) – (0.543 log ) • = apparent viscosity in Pa s T = temperature in C  = strain rate in s-1 Lavallée et al. (2007) Geology 35:843-846