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Title: Effect of particle entrainment on the runout of pyroclastic density currents

Pyroclastic density currents (PDCs) can erode soil and bedrock, yet we currently lack a mechanistic understanding of particle entrainment that can be incorporated into models and used to understand how PDC bulking affects runout. We quantify how particle splash, the ejection of particles due to impact by a projectile, entrains particles into dilute PDCs. We use scaled laboratory experiments to measure the mass of sand ejected by impacts of pumice, wood, and nylon spheres. We then derive an expression for particle splash that we validate with our experimental results as well as results from seven other studies. We find that the number of ejected particles scales with the kinetic energy of the impactor and the depth of the crater generated by the impactor. Last, we use a one-dimensional model of a dilute, compressible density current—where runout distance is controlled by air entrainment and particle exchange with the substrate—to examine how particle entrainment by splash affects PDC density and runout. Splash-driven particle entrainment can increase the runout distance of dilute PDCs by an order of magnitude. Furthermore, the temperature of entrained particles greatly affects runout and PDCs that entrain ambient temperature particles runout farther than those that entrain hot particles. Particlemore » entrainment by splash therefore not only increases the runout of dilute PDCs but demonstrates that the temperature and composition of the lower boundary have consequences for PDC density, temperature, runout, hazards and depositional record.« less
Authors:
 [1] ;  [1] ;  [2]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Earth and Planetary Science
  2. Univ. of California, Berkeley, CA (United States). Dept. of Earth and Planetary Science. Dept. of Civil and Environmental Engineering
Publication Date:
Grant/Contract Number:
AC02-05CH11231; EAR1144198; EAR1447559
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 121; Journal Issue: 9; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Research Org:
Univ. of California, Berkeley, CA (United States)
Sponsoring Org:
USDOE; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Splash Function; pyroclastic surge; liftoff; particle impact; sedimentation; bulking
OSTI Identifier:
1480733

Fauria, Kristen E., Manga, Michael, and Chamberlain, Michael. Effect of particle entrainment on the runout of pyroclastic density currents. United States: N. p., Web. doi:10.1002/2016JB013263.
Fauria, Kristen E., Manga, Michael, & Chamberlain, Michael. Effect of particle entrainment on the runout of pyroclastic density currents. United States. doi:10.1002/2016JB013263.
Fauria, Kristen E., Manga, Michael, and Chamberlain, Michael. 2016. "Effect of particle entrainment on the runout of pyroclastic density currents". United States. doi:10.1002/2016JB013263. https://www.osti.gov/servlets/purl/1480733.
@article{osti_1480733,
title = {Effect of particle entrainment on the runout of pyroclastic density currents},
author = {Fauria, Kristen E. and Manga, Michael and Chamberlain, Michael},
abstractNote = {Pyroclastic density currents (PDCs) can erode soil and bedrock, yet we currently lack a mechanistic understanding of particle entrainment that can be incorporated into models and used to understand how PDC bulking affects runout. We quantify how particle splash, the ejection of particles due to impact by a projectile, entrains particles into dilute PDCs. We use scaled laboratory experiments to measure the mass of sand ejected by impacts of pumice, wood, and nylon spheres. We then derive an expression for particle splash that we validate with our experimental results as well as results from seven other studies. We find that the number of ejected particles scales with the kinetic energy of the impactor and the depth of the crater generated by the impactor. Last, we use a one-dimensional model of a dilute, compressible density current—where runout distance is controlled by air entrainment and particle exchange with the substrate—to examine how particle entrainment by splash affects PDC density and runout. Splash-driven particle entrainment can increase the runout distance of dilute PDCs by an order of magnitude. Furthermore, the temperature of entrained particles greatly affects runout and PDCs that entrain ambient temperature particles runout farther than those that entrain hot particles. Particle entrainment by splash therefore not only increases the runout of dilute PDCs but demonstrates that the temperature and composition of the lower boundary have consequences for PDC density, temperature, runout, hazards and depositional record.},
doi = {10.1002/2016JB013263},
journal = {Journal of Geophysical Research. Solid Earth},
number = 9,
volume = 121,
place = {United States},
year = {2016},
month = {9}
}