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. Williams 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 pose a bigger threat not only to buildings but humans as well.
More importantly, there are negative impacts of using volcanic ash
on roofs that readers should know beforehand. 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.
A hazard that pose a bigger threat is called pyroclastic density
current(PDC). Majority of fatalities from volcanic hazards comes from 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). Linking
back to the simulation done by Williams and the scientists, launching volcanic
rocks, the size of large boulders, to accurately test the impact on structures was
sceptical. 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.
Another
hazard is 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 are not be taken lightly and measures to mitigate exposure should be included
in the article for education purposes.
Overall,
Williams could cover more content on the other volcanic hazards. He should also
take in account for the difficulties of using volcanic ash on roofs as the
disadvantages easily outweigh the advantages.
References
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
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
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
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
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