In the article
“How Volcanic Ash Strengthens A Roof Against Powerful Projectiles”, Williams
(2019) states that the addition of volcanic ash layers on the roofs can
mitigate the impact of volcanic projectiles on shelters around active
volcanoes.
Williams claims
that scientists had discovered mountain huts were capable of providing
life-saving shelter for hikers during the eruption that took place at Mount
Ontake, Japan 2014. This finding inspired the scientists to further study on
how the addition of volcanic ash on roofs could reduce impacts of projectiles.
Through meticulous simulation, scientists were able to deduce that the
thickness of ash deposit is proportional to the roofs’ energy absorption rate
from projectiles. Five centimeters of ash layer tripled the strength of the
roof from projectiles. However, heavier loads of ash may affect the structural
integrity of the roof.
Additionally,
he states that scientists expected buildings to take more damage from multiple
volcanic hazards as compared to one. Tests proved otherwise, on condition that
tephra is placed on roofs before impacts. Willams concludes that researchers
will conduct further investigation to determine the optimum range of ash
deposit layers to achieve a balance between reducing impact of projectiles and
risk of roof collapsing. While the article does focus on using
volcanic ash to shield the roof of buildings nearby volcanic areas from volcanic
projectiles, it lacks the information on other hazards of a volcanic eruption
that poses a bigger threat not only to buildings but humans as well.
Majority of fatalities from volcanic hazards comes from a hazard
called pyroclastic density current (PDC) (Brown et al., 2017). PDC contains a mixture of volcanic gas, ash
and rock fragments. These rock fragments can be as large as boulders that
travel at a very high velocity destroying majority of structures in their trail,
to the extend where reinforcement rods in concrete can crook towards the flow
of PDC (USGS, 2016). In my opinion, linking back to the simulation done by
Williams and the scientists, I believed that they could not have launched
volcanic rocks, the size of large boulders, to accurately test the impact on structures.
The launching and projectile speed had to be on par with a volcanic eruption
speed. In addition, the simulation did not specify what volcanic rock sizes were
used for the experiment thus readers may find the results to not be credible.
To
add on, a hazard that poses a big threat to humans are volcanic gases. Substantial
amounts of sulfur dioxide, carbon dioxide, hydrogen sulfide can be released
from volcanoes and high doses of these gases are harmful to the human body
(USGS, 2017). In 1986, high amounts of carbon
dioxide were released from Lake Nyos and killed about 1700 people (Nasr, 2009).
Sulfur dioxide and hydrogen sulfide are similar whereby they affect our
respiratory system and prolong high exposure to humans will result in death (USGS,
2017). These gases should not be taken lightly, and measures should be included
in the article for education purposes.
More
importantly, there are negative impacts of using volcanic ash on roofs that were
not emphasized. Maintenance for using volcanic ash is high and personal
protective gear must be used when handling it. Due to ash being on the roofs, it
is exposed to wind and rain. Ash may be blown away towards drainage pipes and
corrode or block the water flow, leading to poor water hygiene (USGS, 2015). “When
ash is wet , static loads may increase by up to hundred percent.” (USGS, 2015),
which will cause a roof to collapse.
Overall,
Williams could cover more content on the other volcanic hazards. I feel the disadvantages
of using volcanic ash on buildings outweighs the positive impacts stated in the
article.
References
Nasr, S.L. (2009, March
24) How did Lake Nyos suddenly kill 1,700 people? . Retrieved from https://science.howstuffworks.com/environmental/earth/geophysics/lake-nyos.htm
Williams,G.T. (2019, November 12). How Volcanic Ash
Strengthens A Roof Against Powerful Projectiles. Earth Observatory Blog.
Retrieved from
https://www.earthobservatory.sg/blog/how-volcanic-ash-strengthens-roof-against-powerful-projectiles
Brown, S.K., Jenkins, S.F., Sparks, Sparks, R.S.J., Odbert,
H., Auker, M.R. (2017). Volcanic fatalities database: analysis of
volcanic threat with distance and victim classification. Journal of
Applied Volcanology. https://doi.org/10.1186/s13617-017-0067-4
U.S.
Geological Survey. (2016, February 12). Pyroclastic
flows move fast and destroy everything in their path. https://volcanoes.usgs.gov/vhp/pyroclastic_flows.html
U.S.
Geological Survey. (2017, May 10). Volcanic gases can be harmful to health,
vegetation and infrastructure. https://volcanoes.usgs.gov/vhp/gas.html
U.S.
Geological Survey. (2015, December 17). Volcanic Ash Impacts &
Mitigation: Buildings. https://volcanoes.usgs.gov/volcanic_ash/buildings.html
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