Exercise 2: Possible disasters
Objective: Analyse the possible threat of volcanic ash to the towns around the Villarrica volcano. To do this you will need to consider the size of the volcano, its distance from the population centre, as well as the topography, geomorphology and hydrology characteristics of the volcano.
This exercise will look at various possible scenarios of natural disasters in the region.
Data: For this exercise you will use the same data as in exercise 1, together with the GIS layers showing towns and volcanoes. These .shp layers can be downloaded from the menu on the right.
Inspection of the volcano and its surroundings
The surroundings of the Villarrica volcano, including the town of Pucón near the lake
Use the Villarrica-RGB-4-5-3.tif image created in Exercise 1.
Zoom in to study the surroundings of the volcano, and describe the mountains, valleys, and courses of water.
Measuring distances between volcanoes and population centres
Zoom into the Villarrica volcano, located at coordinates 1070, 1620. To do this you must use the Pixel info inspection tool.
With the Measure Tool, measure the area and perimeter of the dark lava and ash field. Measure the average diameter of the snow-covered cone of the volcano.
Use the same procedure to measure the area and perimeter of the two following towns:
Villarrica: located at coordinates 214, 1039.
Pucón: located at coordinates 946, 1036.
Using the same method, measure the distance between the population centres and the volcanic cone.
Villarrica - Villarrica Volcano
Pucón - Villarrica Volcano
Task
Isolines indicating the distribution of volcanic ash (in cm) after the last eruption of Lonquimay
This figure was produced after the 25 December 1988 eruption of the Lonquimay volcano. It shows the accumulation of volcanic ash (in cm) caused by the eruption.
Discuss the distribution characteristics of the ash and explain its shape.
What influences its shape?
Identify the town of Lonquimay.
How far away from the crater is the town located?
What damage is it likely to cause people, houses, agriculture and forest?
How far from the crater did the ash fall?
What would happen if the Villarrica volcano had a similar eruption?
Using the observations above, can you evaluate the potential damage to the cities of Pucón and Villarica if the Villarrica volcano had a similar eruption?
The measurement tool can help in this task, but we will also use the two GIS layers:
Towns.shp
Volcanoe.shp
Display the two layers on top of the Villarrica-RGB-4-5-3.tif image.
Open the GIS/Vector processing/Buffer zone tool. Try to construct different buffers showing different ash distributions.
Should there be a new eruption of the Lonquimay volcano, would the two towns be in danger?
Create a map showing the potential danger of a future eruption.
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