@article{fdi:010072327,
  title = {{G}ranular fingering as a mechanism for ridge formation in debris avalanche deposits : laboratory experiments and implications for {T}utupaca volcano, {P}eru},
  author = {{V}alderrama, {P}. and {R}oche, {O}livier and {S}amaniego, {P}ablo and des {V}ries, {B}. {V}. and {A}raujo, {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he origin of subparallel, regularly-spaced longitudinal ridges often observed at the surface of volcanic and other rock avalanche deposits remains unclear. {W}e addressed this issue through analogue laboratory experiments on flows of bi-disperse granular mixtures, because this type of flow is known to exhibit granular fingering that causes elongated structures resembling the ridges observed in nature. {W}e considered four different mixtures of fine (300-400 mu m) glass beads and coarse (600-710 mu m to 900-1000 mu m) angular crushed fruit stones, with particle size ratios of 1.9-2.7 and mass fractions of the coarse component of 5-50 wt%. {T}he coarse particles segregated at the flow surface and accumulated at the front where flow instabilities with a well-defined wavelength grew. {T}hese formed granular fingers made of coarse-rich static margins delimiting fines-rich central channels. {C}oalescence of adjacent finger margins created regular spaced longitudinal ridges, which became topographic highs as finger channels drained at final emplacement stages. {T}hree distinct deposit morphologies were observed: 1) {J}oined fingers with ridges were formed at low (<= 1.9) size ratio and moderate (10-20 wt%) coarse fraction whereas 2) separate fingers or 3) poorly developed fingers, forming series of frontal lobes, were created at larger size ratios and/or higher coarse contents. {S}imilar ridges and lobes are observed at the debris avalanche deposits of {T}utupaca volcano, {P}eru, suggesting that the processes operating in the experiments can also occur in nature. {T}his implies that volcanic (and non-volcanic) debris avalanches can behave as granular flows, which has important implications for interpretation of deposits and for modeling. {S}uch behaviour may be acquired as the collapsing material disaggregates and forms a granular mixture composed by a right grain size distribution in which particle segregation can occur. {L}imited fragmentation and block sliding, or grain size distributions inappropriate for promoting granular fingering can explain why ridges are absent in many deposits.},
  keywords = {{D}ebris avalanche ; {G}ranular fingering ; {R}idge ; {G}ranular flow ; {A}nalogue experiments ; {PEROU} ; {TUTUPACA} {VOLCAN}},
  booktitle = {},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {349},
  numero = {},
  pages = {409--418},
  ISSN = {0377-0273},
  year = {2018},
  DOI = {10.1016/j.jvolgeores.2017.12.004},
  URL = {https://www.documentation.ird.fr/hor/fdi:010072327},
}