One of the great challenges after volcanic eruptions: Clean-up

A day or so after a volcano erupts media often reports on the clean-up operations undertaken when the volcanic ash (or tephra) is dispersed by winds and deposited on communities. I thought I would use this blog post to summarise a key finding of a recently published review paper by colleagues and myself (available here for free until 14 November).

The video above from the recent Calbuco eruption in Chile shows that ash is incredibly disruptive to society and potentially damaging to property. One of the key methods of reducing the impacts ash can have on a community is to efficiently clean-up and dispose of it where it can be managed. It is for this reason that clean-up operations often involve the mobilisation of large workforces to remove the ash.

A man sweeping ash from the road during the 2014 eruption of Kelud (photo credit: Crisco 1492)

One of the most interesting findings from our paper was that there appears to be a somewhat inherent scale of response across the 30 different clean-up operations all over the world spanning about 50 years.

Removal of volcanic ash during coordinated clean-up operations. Dashed-dotted line indicates 100% removal. (Note: graph changed from published version for copyright purposes, see paper for full details)

I don’t want to dwell on some of the details of the graph (see the paper for specifics) but essentially what it shows is the amount of volcanic ash deposited on a community (x-axis) and the amount of volcanic ash removed and disposed of from the community (y-axis) during coordinated clean-up operations (municipal operations). For clarity, 1,000 m3/km2 is roughly consistent with about 1 mm thickness across a city (10,000 m3/km2 = 1 cm… etc).

If communities removed 100% of volcanic ash the trend would follow the dashed-dotted line. Clearly this isn’t the case. What this suggests is for low amounts of ash (1 mm) just a few percent is removed and disposed (note log scale). Whereas for large amounts (30-40 cm) a much higher percentage is removed. We suggest one of the reasons for this is that the amount of ash removed is consistent with some of the common thresholds given for volcanic ash impacts in urban areas. At low levels municipal authorities concentrate on cleaning roads and leave private property owners to deal with any clean-up on their own. At greater ash thickness it then becomes necessary for municipal authorities to provide assistance to private property owners to clean-up as the volume of ash on a property can become very large.

This provides useful information for municipal authorities as well as for those modelling volcanic impacts and risks which until now have relied on very limited evidence.

The full paper is available free until November 14 from here.

Follow me on twitter: @naturehazard or at The Geohazards Blog.

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Developing: Volcanic eruption at Mount Aso

Volcanic eruption of Mount Aso, Japan.

Mount Aso, located on the southern island of Kyushu, erupted on Monday 14 September. The eruption reportedly sent an ash column 2,000 m into the air. Currently there are no reports of damage or injuries.

Reports indicate that tourists near the volcano have been safely evacuated and the volcanic alert is currently at 3 (5 point scale). The area around the volcano had been on alert previously. In May, alert was raised to 5, resulting in evacuations.

Volcanic Alert Level (taken from http://www.jma.go.jp/en/volcano/map_6.html)

See below tweet for a photo taken from a passing aircraft.

Japan Airlines has since reportedly cancelled flights through the area.

EDIT (10:45pm GMT, Sept 14): It is being speculated that the eruption could be stream driven phreatomagmatic eruption. Meanwhile, the impact on aviation has some more detail with at least 20 flights cancelled, and more expected to be either cancelled or disrupted. In total, 30 people were evacuated from the volcano, and access is closed within a 4 km wide area of the volcano.

EDIT (01:35am GMT, Sept 15): Brad Scott from GNS Science in New Zealand has written about the simularities between the eruption of Mount Aso and an eruption at the 2012  Te Maari eruptions.

This post will be updated as new developments are reported.

 

What could happen if the Volcan de Colima eruption goes Plinian?

On Thursday 9th July 2015, Volcan de Colima (Volcano of Fire) in Mexico began erupting. Check out the webcam for live images!

Information is a little scarce at this stage, and some information is a little contradictory but the Denver Post has some nice images. Additionally, there are some nice images appearing on twitter.

The village of  Yerbabuena is estimated to have received about 5 cm of volcanic ash fall due to the eruption, and ash fall has reached as far as Colima City.

Many settlements are located around Volcan de Colima

There are three scenarios of how the situation could evolve:

  • A gradual waning of activity in coming weeks
  • A 1913-like explosion
  • A collapse of the volcano’s dome

Officials from Mexico’s civil protection authority have described the behaviour as atypical and not seen since the last major eruption over 100 years ago on January 18-24 1913. This has raised some concerns that the current activity could evolve into a more major eruption, or what volcanologists call a “Plinian eruption”. A plinian eruption is the biggest of all the eruption styles.

The 1913 eruption and what could happen if a Colima goes Plinian.

Pyroclastic flows

During the 1913 Plinian style eruption of Colima volcano, an eruption column rose to more than 20 km above the volcanoes crater. Eventually, due to the weight of the upper part of the column, the eruption column collapsed resulting in what is called a “pyroclastic flow”. A pyroclastic flow is a fast moving, extremely hot torrent of gas, volcanic ash, and blocks. The eruption of Volcan de Colima in 1913 resulted in the deaths of eight people. However in the last 100 years substantial population growth has occurred in the region. It has been estimated that a similar pyroclastic flow today could impact on about 15,000 people.

Pyroclastic flows are almost always deadly to those that they contact, and incredibly destructive to buildings. Additionally, due to the level of destruction and amount of volcanic material they bring with them they can cause the abandonment of settlements, as has happened to Plymouth, the capital city on the island of Montserrat due to the eruption of Soufriere Hills volcano. 

Lahars

Lahars are also a problem when rainfall interacts with unconsolidated materials that are erupted from volcanoes. It is currently the rainy season in the area, and so the threat to communities around the volcano from lahars could be large, even if the eruption does not become plinian.

Ash fall

Volcanic ash fall is the particles from the eruption column being dispersed largely by wind and falling to the ground. Volcanic ash can fall great distances from the source volcano. Although, it is not usually deadly, volcanic ash fall can be disruptive to everyday life due to impacts on:

In addition, it often must be cleaned up which can be extremely time consuming, expensive, and labour intensive.

A research article in 2010 by Rita Fonesca and Ana Lillian Martin Del Pozzo explained the potential elements exposed to volcanic ash if the 1913 eruption were to occur today. To summarise some of the findings:

  • It was estimated that the 1913 eruption resulted in wide spread volcanic ash which affected over 700,000 people. Again, due to population growth this number would be around 5 million today. Previous eruptions have resulted in volcanic ash fall in Mexico City, which today has a population of over 20 million.
  • Much of the population in the area works in the farming industry, and so the impact of a plinian style eruption on agriculture could be large. This would be problematic for the region as agriculture is important in both local and regional economies.
  • There are 14 international airports now located in the area that was impacted by the 1913 eruption. This would significantly impact air travel in the area as airport often must close due to volcanic ash in the air space or to clean-up fallen volcanic ash on the airport. This is because volcanic ash is extremely abrasive and can be very damaging to planes. In addition, when planes take off or land they can spread the volcanic ash to other areas.
  • There are a number of important highways in the areas which connect the region to major cities.

At this stage it is difficult to determine whether Volcan de Colima will indeed become Plinian, and so it is important that we recognise that it is not a certainty. However, given what the 1913 eruption could do today, it is important to recognise what could potentially occur to develop appropriate preparedness plans.

I will be watching Volcan de Colima’s development with great interest.