Characteristics of debris avalanche deposits inferred from source volume estimate and hummock morphology around Mt. Erciyes, central Turkey

Abstract

Abstract. Debris avalanches caused by volcano sector collapse often form characteristic depositional landforms such as hummocks. Sedimentological and geomorphological analyses of debris avalanche deposits (DADs) are crucial to clarify the size, mechanisms, and emplacement of debris avalanches. We describe the morphology of hummocks on the northeastern flank of Mt. Erciyes in Kayseri, central Turkey, likely formed in the late Pleistocene. Using a remotely piloted aircraft system (RPAS) and the structurefrom-motion and multi-view stereo (SfM-MVS) photogrammetry, we obtained high-definition digital elevation model (DEM) and orthorectified images of the hummocks to investigate their geometric features. We estimated the source volume of the DAD by reconstructing the topography of the volcano edifice using a satellite-based DEM. We examined the topographic cross sections based on the slopes around the scar regarded as remnant topography. Spatial distribution of hummocks is anomalously concentrated at a certain distance from the source, unlike those that follow the distance-size relationship. The high-definition land surface data by RPAS and SfM revealed that many of the hummocks are aligned toward the flow direction of the debris avalanche, suggesting that the extensional regime of the debris avalanche was dominant. However, some displaced hummocks were also found, indicating that the compressional regime of the flow contributed to the formation of hummocks. These indicate that the flow and emplacement of the avalanche were constrained by the topography. The existing caldera wall forced the initial eastward flow to move northward, and the north-side caldera wall forced the flow into the narrow and steepened outlet valley where the sliding debris underwent a compressional regime, and out into the unconfined terrain where the debris was most likely emplaced on an extensional regime. Also, the estimated volume of 12-15 × 10 8 m 3 gives a mean thickness of 60-75 m, which is much deeper than the reported cases of other DADs. This suggests that the debris avalanche must have flowed further downstream and beyond the current DAD extent. Assessments of the DAD incorporating the topographic constraints can provide further insights into the risk and mitigation of potential disasters in the study area.

Review article: the use of remotely piloted aircraft systems (RPASs) for natural hazards monitoring and management

“…Environmental and geological monitoring can profit from fast multi-temporal acquisitions delivering high-resolution images (Thamm and Judex, 2006;Niethammer et al, 2010). RPASs can also be considered a good solution for mapping and monitoring different active processes at the earth's surface (Fonstad et al, 2013;Piras et al, 2017;Feurer et al, 2017;Hayakawa et al, 2018) such as at glaciers (Immerzeel et al, 2014;Ryan et al, 2015;Fugazza et al, 2017), Antarctic moss beds (Lucieer et al, 2014b), coastal areas (Delacourt et al, 2009;Klemas, 2015), interseismic deformations (Deffontaines et al, 2017(Deffontaines et al, , 2018 and in river morphodynamics (Gomez and Purdie, 2016;Jaud et al, 2016;Aicardi et al, 2017;Bolognesi et al, 2016;Benassai et al, 2017), debris flows (Wen et al, 2011) and river channel vegetation (Dunford et al, 2009).…”

Hummocky terrain of the Kalibabak debris avalanche deposit, Lombok Island, Indonesia

“…the Topographical map of Indonesia (known as RBI map) (1 : 25 000) and the Geological Map sheet of Lombok (1 : 250 000) which is useful for lithological identification at a regional scale. Due to the common small dimension of hummocks (10 m 2 to 100 m 2 in area), an elevation model derived from a paired aerial photograph and airborne laser scanner would have provide more accurate data [8], but the acquisition process would have been too costly at the scale of this study.…”

“…centroid, distance to crater, relative height, area (perimeter, major and minor axis), sinuosity, axis ratio, circularity index, volume, slope, and aspect (as well as its piedmont) [4]. For reconstructing the estimated volume and the volcano edifice prior to emplacement, the variables are reduced only seven parameters, namely distance to the source, area, top height, volume, major and minor axis, elongated ratio, and displacement angle [8].…”

Preface: The use of remotely piloted aircraft systems (RPAS) in monitoring applications and management of natural hazards

“…The geomorphological description and the potential risk of debris avalanche (i.e. a particular type of landslide) deposits related to the collapse of a volcano sector is presented by Hayakawa et al (2018). Hayakawa obtained a high-resolution DTM using RPAS that was fundamental for the geomorphological description of the studied area.…”

“…The use of RPAS in post-earthquake scenarios is described by Cannioto et al (2017), who presented how RPAS could help during search and rescue activities with the recognition of the shortest survey path in highly damaged areas. The use of RPAS for emergency investigation is described by Huang et al (2017), who describe a methodological approach for the use of RPAS for emergency investigations of a single geo-hazard mission.…”