Controls on accumulation of a volcaniclastic fan, Ruapehu composite volcano, New Zealand

摘要: The Whangaehu fan is the youngest sedimentary component on eastern ring plain surrounding Ruapehu volcano. Fan history comprises constructional (830–200 years bp) and dissectional (<200 phases. phase includes four aggradational periods associated with both syneruptive inter-eruptive behavior. All began when deposition by large lahars changed flow conditions from channelized to unchannelized. Subsequent behavior was a function of rate sediment influx fan. influx, in turn, controlled frequency magnitude volcanic eruptions, short-term climate change, amount stored volcano flanks. Fanwide aggradation occurred rates were high enough maintain unchannelized surface. Maintenance an undissected surface required sedimentation frequent that prevented major dissection between events. These best met during eruptive episodes eruptions blanketed flanks tephra lahar initiation high. During episodes, volcanism primary control sedimentation. Climatic variations do not influence accumulation. Local too small across entire In this case, only channel system received much following initial lahar. This localized if (1) reservoir flank for floods bulk into debris flows (2) events supply some parts minor episodes. cases, remained previous intervals. Periods increased storm activity produced bulked relatively flows. When depleted, entered present phase. Syneruptive noneruptive are mostly bypasses deposits rapidly reworked. case at Ruapehu, even though episode favors generation intense floods.