Table 1.

Post-depositional processes affecting ignimbrites

Process		Time scale	Features/effects	Example	Reference
Internal (lithological)	Deaeration	Minutes to years	Density increase	Mt. St. Helens, laboratory experiments	Wilson and Head 1981; Rowley et al. 1981; Druitt et al. 2004, 2007
	Welding	Minutes to days	Eutaxitic fabric, fiamme, joints	Bishop Tuff, Murga Caldera Ignimbrites	Ross and Smith 1961; Sparks et al. 1999
	Rheomorphism	Minutes to hours to days	Flow lineations, deposit thickness variations, eutaxitic fabric	Borrowdale Volcanic Group, TL Ignimbrite	Schmincke and Swanson 1967; Sumner and Branney 2002; Branney et al. 2004
	Compaction	Weeks to decades	Fracture network, subsidence	Grants Ridge Tuff, Lascar pumice flow deposit	Keating and Valentine 1998; this work
	Cooling	Years	Joints	Bishop Tuff	Sheridan 1970
	Indurationa	Decades to millions of years	Hardening, fumarolic incrustations, mounds and ridges	Valley of 10,000 Smokes; Bishop Tuff; Akdag-Zelve Ignimbrite; Mazama-Crater Lake	Griggs 1922; Sheridan 1970; Schumacher and Mues-Schumacher 1997; Bacon 2008
External (environmental)	Aeolian erosion	Days to millions of years	Yardangs, pits	Tara Ignimbrite	Bailey et al. 2007
	Fluvial erosion	Days to decades	Gullies, channels	Atana Ignimbrite	Bailey et al. 2007
	Mass wasting	Days to millennia	Fractures, debris flows, lahars	Pinatubo	Pierson et al. 1992
	Remobilization	Days to years	Secondary pyroclastic flow deposits	Pinatubo	Torres et al. 1996
	Seismic perturbation	Weeks to decades	Pyroclast reorganization	Gramts Ridge Tuff, Poris Ignimbrite, Lascar pumice flow deposit	Keating and Valentine 1998; Brown and Branney 2004; this work
	Tectonic deformation	Millions of years	Lineaments, alluvial fans	La Pacana Ignimbrites	Riquelme et al. 2003

^aPartially controlled by external forcing