Lahar characteristics as a function of triggering mechanism at a seasonally snow-clad volcano: contrasting lahars following the 2014 phreatic eruption of Ontake Volcano, Japan

Earth, Planets and Space

Table 2 Mineral assemblages of 2014 primary eruption, October rain-triggered lahar, and April ROS-triggered lahar deposits identified by XRD

Sample name	Description	Qz	Pl	Crs	Py	Gp	Anh	Alu	Prl	Sme	Ilt	Kln	I/S	Chl
September 2014 primary deposits
On-1	Ashfall (Tanohara parking lot; bulk)	+	+	+	+	+	+	+		+	+	+
On-64	Ashfall (Ishimuro Sanso hut; lower part)	+	+	+	+	+	+	+	+	+		+
On-65	Aggregates of ashfall (Ishimuro Sanso hut; upper part)	+	+	+	+	+	+	+	+		+	+
On-44	Ash cloud deposits (Akagawa, upstream end)	+	+	+	+	+	+	+	+	+	+	+		+
October 2014 rain-triggered lahar
On-13	Cohesive debris flow deposits (Nigorigawa, downstream end)	+	+	+	+	+	+	+	+	+	+	+	+	+
On-18	Cohesive debris flow deposits (Akagawa, overbank facies)	+	+	+	+	+	+	+	+	+		+	+	+
On-34	Cohesive debris flow deposits (Akagawa, bottom part)	+	+	+	+	+	+	+	+	+	+	+		+
On-45	Cohesive debris flow deposits (Akagawa, upstream end)	+	+	+	+	+	+	+	+	+	+	+	+	+
April 2015 rain-on-snow-triggered lahar deposits (mud drape)
On-21	Rain-on-snow lahar deposits (Akagawa)	+	+	+	+		+	+	+	+	+	+	+	+

Qz quartz, Pl plagioclase, Crs cristobalite, Py pyrite, Gp gypsum, Anh anhydrite, Alu alunite, Prl pyrophyllite, Sme smectite, Ilt illite, Kln kaolin group minerals (7Å), I/S illite/smectite mixed layer, Chl chlorite