Reader Response: Final Draft

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 investigations to determine the optimum range of ash deposit layers to achieve a balance between reducing impact of projectiles and risk of roof collapsing.

Although the article claims that utilizing volcanic ash can benefit cities near volcanoes, it failed to consider the disadvantages volcanic ash can bring.  

The first disadvantage arising from volcanic ash usage is the additional load imposed on roofs, causing roofs to collapse. Williams (2019) states that adding five centimetres of ash layer triple the strength of the roof, however the researchers fail to take into consideration the ash produced when volcanoes erupt. Volcanic ash consists of particles that has low density and can travel long distances, carried by winds. The ash in the sky will eventually fall to the roof; this phenomenon is known as ash fall and it leaves a thick layer of ash on roofs. When existing tephra cushioned structures are subjected to additional volcanic ash from the ash fall phenomenon, it is possible that the thickness of ash deposit will increase. According to United States Geological Survey (USGS) (2015), ash fall can potentially cause the collapse of buildings if the thickness exceeds 100mm. The likelihood of a roof collapse is higher if the ash accumulated is wet. This is supported by a documented incident that took place in Philippines which claimed 300 lives. This incident was caused by the “collapse of roofs from the ash load on roofs during the explosive eruption of Mt. Pinatubo on June 15, 1991” (United States Geological Survey, 2015).

Another disadvantage that the researchers fail to address is the limitation of the experiment conducted. Williams et al. (2019) state that researchers needed to observe and study the effect of tephra cushioning but are unable to do so because of the extreme dangers associated with close observation of impacts around volcanoes. To prove that tephra cushioning is effective against impacts from volcanic projectiles, researchers used a real-life simulation to project volcanic rock on reinforced concrete (RC) with and without tephra cushioning. The experiment may not be accurate as there are factors that can affect the accuracy of the experiment. One of the factors is the life-span of the materials in a structure. The longer the life-span of the structure, the weaker strength it has to withstand impacts compare to a new structure. This can result in the experiment to overestimate or underestimate the amount of energy tephra can withstand. According to the article “Journal of Volcanology and Geothermal Research”, Williams (2019) claims that the RC used during experiment was less than a year old and thus be overestimating the resistance of tephra layers. Williams also claims that the tiles were bought from a junkyard and the age of the materials were unknown. Therefore, the accuracy of the result of tephra withstanding impacts from volcanic projectiles does not truly reflect the real consequences. 

Lastly, long or short term exposure to volcanic ash is detrimental to the health of the residents. Williams (2016) states that short term exposure to volcanic ash can cause individuals to have respiratory problems, eye problems and skin irritation. Williams also claims that volcanic ash can cause silicosis, which can be fatal even with treatment; and affect the quality of water by contaminating it.

Although volcanic ash had been proven to be beneficial to people, the disadvantages of utilizing it may do more harm than good. Ideally, it may appear to be a protection layer but in reality it can bring unnecessary disaster to people. Researchers should conduct more experiments and consider the disadvantages of using volcanic ash.

References

Williams, G., Kennedy, Ben M., Lallemant, D., Wilson, T., Allen, N., Scott, A., … Jenkins, S. (2019, 11). Tephra cushioning of ballistic impacts: Quantifying building vulnerabiltiy through pneumatic cannon experiments and multiple fragility curve fitting approaches. 11-14(5.2) Retrieved from Research Gate: https://www.researchgate.net/publication/337083288_Tephra_cushioning_of_ballistic_impacts_Quantifying_building_vulnerability_through_pneumatic_cannon_experiments_and_multiple_fragility_curve_fitting_approaches

Survey, U. S. (2015, 12 09). Volcanic Ash Impacts & Mitigation. Retrieved from Volcanic Ashfall Impacts: https://volcanoes.usgs.gov/volcanic_ash/roof_loading.html

Williams, G. (2016, November 14). Volcanic Ash: More Than Just A Science Project. Retrieved from Geology and Human Health: https://serc.carleton.edu/NAGTWorkshops/health/case_studies/volcanic_ash.html