Reader response draft 2

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 this is a good discovery and can be helpful against volcanic projectiles, 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 has the risk of overloading the roof and causing it to collapse. Yamamoto et al. (2016) 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 their rooftops from the Mount Ontake eruption. 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.

In conclusion, 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

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.

https://www.universetoday.com/29667/volcano-dangers/

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