Characteristics of debris avalanche deposits inferred from source volume estimate and hummock morphology around Mt. Erciyes, central Turkey
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...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-02-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | https://www.nat-hazards-earth-syst-sci.net/18/429/2018/nhess-18-429-2018.pdf |
| Summary: | 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 structure-from-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<sup>8</sup> m<sup>3</sup> 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. |
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| ISSN: | 1561-8633 1684-9981 |