This section ends with a massive
ignimbrite section of variable thickness that is mapped as a non-formal unit (Butalon
ignimbrite) because of its important surface development crowning the main hills in the region (Fig.
All three chronosequences were on the Taupo Pumice soil (Immature Orthic Pumice Soil; Hewitt 1998), formed on the non-welded Taupo
ignimbrite (of rhyolitic composition) deposited as a pyroclastic flow around AD 232 (Hogg et al.
(2004) used an airborne laser scanner to survey an area of the 1998 Fukushima disaster, where more than 1,000 shallow landslides occurred on slopes of vapor-phase crystallized
ignimbrite overlain by permeable pyroclastics.
The AD 186 Taupo eruption, when 60 [km.sup.3] of rhyolitic pumice and
ignimbrite were discharged from a vent located in present-day Lake Taupo, provided the parent material of most soils in the catchment.
Abstract: The dry ecosystems in the
ignimbrite meseta of Guanacaste, northwest Costa Rica is mapped.
In the igneous sector, steeply foliated, crystalpoor
ignimbrite is intruded by a dome of aphanophyric (roof facies?) rhyolite.
Overburden consists mainly of recent volcanic
ignimbrite: hard, competent rocks which should allow steep pit slopes, although between them and the ore there is a layer of palaeo gravels which would call for a wide safety bench in the mine.
2001; Bennett, 2009; Olguin-Villa, 2010; Olguin-Villa et al, 2010), and in the state of Sonora where it is described as peralkaline
ignimbrite (Vidal Solano et al, 2005, 2007, 2008a; Barrera-Guerrero and Vidal-Solano, 2010; Gomez-Valencia and Vidal-Solano, 2010).
Schaefer (1995) established a main age for the Rio Claro
ignimbrite (formed about 100 ka ago) that defined the limit between the Older and Present Ruiz.
The ancient eruption would have been accompanied by a steady rain of volcanic ash and superheated rocks, along with earthquakes and fast-flowing rivers of lava and hot mud, or
ignimbrite.