Reader's response Draft 1
In the article, “How Volcanic Ash Strengthens
a Roof Against Powerful Projectiles,” Williams (2019) proposes that having a
layer of volcanic ash on the rooftops of building can increase protection from
volcanic projectiles. He mentions that a study by scientists from the Earth
Observatory of Singapore (EOS) and the University of Canterbury (UC) was
conducted to measure the ability of ash to cushion volcanic projectile impacts
shot by a high-pressure air cannon, in which tests show that having a five
centimeters ash layer tripled the strength of the roof to withstand
projectiles. He notes that while a thicker layer helps, it increases the risk
of the roof collapsing. He states that scientists also believed that buildings
would be more damaged when struck by multiple projectiles compared to one.
However, the tests proved otherwise, provided that the roof is protected with a
5cm layer of tephra. Nonetheless, he remarks that this method should be done on
an individual basis by ensuring the shelter benefits from the tephra on its
roof, and still withstand its weight. Therefore, he concludes buildings with
reinforced concrete roofs are found to be ideal.
Although I feel this is a good discovery and can
be helpful against volcanic projectiles, I feel that the benefit provided is
negligible compared to the other dangers a house may face in an event of a
volcanic eruption.
Firstly, having a layer of 5cm of ash on the
roof is a good idea by itself, as it can help protect the house from volcanic
projectiles. However, it always had the risk of overloading the roof and
causing it to collapse. Based on a publication by Yamamoto et al. (2016), it mentioned that the ash from the Mount
Ontake eruption could be a danger to the houses nearby the eruption if a large
amount of ash was collected by the roof of a house. Hence, it is clear that
many houses had ash deposited onto its rooftops from the Mount Ontake eruption.
Therefore, if the houses were to have the protective layer of ash in its roofs,
the weight from the additional ash would greatly increase the risk of the
building collapsing.
Secondly, an article from
Ballance (2017) wrote about an experiment, done by the same team from the
University of Canterbury two years before this article, testing if typical
roofs were able to withstand volcanic projectiles by using the same method. The
test showed that for concrete roofs, the projectile was able to penetrate
through it, but it was stopped by the metal reinforcing rods in the concrete.
Hence, from the study, it can be concluded that concrete roofs are generally
good enough to withstand projectiles and protect its occupants, so long as it
has something on the bottom side to prevent the broken pieces of concrete caused by the projectile impact from
potentially causing more damage.
Finally, as stated by
Cain (2009), the danger of volcanic projectiles is minuscule compared to the
other dangers a volcano may pose when it erupts. Depending on the size of an
eruption, houses nearby have no chance against its dangers, ranging from the slow but
extreme force and heat of a lava flow, to pyroclastic flows, when scorching hot
rock and gas flow down the volcano’s sides at speeds greater than 700km/h,
traveling hundreds of kilometers away and annihilating everything in its path.
Even huge boulders have been known to be shot several kilometers away, which
would destroy a house even with the protective layer.
Therefore, I feel the better
thing to research about would be about how to better spot a potential volcano
eruption, and better management on how to evacuate people who would be affected.
References
Yamamoto,
T., Inoue, M. (2016). A Study on sliding characteristic of volcanic ash
deposited on pitched roofs of wooden houses. Journal of Structural and
Construction Engineering (Transactions of AIJ), 81(724):959-969. https://www.researchgate.net/publication/304612578_A_Study_on_sliding_characteristic_of_volcanic_ash_deposited_on_pitched_roofs_of_wooden_houses
Balance, A. (2017). “Will your roof
withstand flying volcanic rocks?”. Our Changing World. https://www.rnz.co.nz/national/programmes/ourchangingworld/audio/201847343/will-your-roof-withstand-flying-volcanic-rocks
Cain, F.
(2009, April 22). Volcano Dangers.
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