Volcanic hazards
Volcanic hazards

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Volcanic hazards

1.1 Volcanic hazards

Ask a friend or a family member to name a volcanic hazard: they will probably say 'lava'. (Try it! It can help you to improve your understanding if you talk to people about your studies.) However, having read this course, you should realise that lava flows are a comparatively minor problem in most cases. Although, except in the rare case of a successful diversion attempt, immovable property is destroyed by lava (Figures 1 and 2), people have to be particularly unfortunate (or stupid) to be killed by a lava flow. You will see a hazardous lava flow in Activity 1.

Figure 1 Burial of a store in Kalapana, Hawaii, between (a) April and (b and c) June 1990 (colour versions of TYVET Figure 5.1).
Figure 1 Burial of a store in Kalapana, Hawaii, between (a) April and (b and c) June 1990 (colour versions of TYVET Figure 5.1).
Figure 2 A burning house in Kalapana, Hawaii, surrounded by a thin sheet of pahoehoe in 1990.
Figure 2 A burning house in Kalapana, Hawaii, surrounded by a thin sheet of pahoehoe in 1990.

Pyroclastic flows are much more dangerous than lava flows. Figure 3 shows two clear views.

Figure 3 (a) The deadly pyroclastic flow on Montserrat in the Caribbean, 25 June 1997 (another view of the event in TYVET Figure 5.8). (b) The thin deposit left by the pyroclastic flow in (a).
Figure 3 (a) The deadly pyroclastic flow on Montserrat in the Caribbean, 25 June 1997 (another view of the event in TYVET Figure 5.8). (b) The thin deposit left by the pyroclastic flow in (a).

Activity 1a The Nyiragongo eruption in 2002

Timing: 30 minutes

Go to the Global Volcansim Program website [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] and click on the 'Reports' tab, then select 'Bulletin of the Global Volcanism Network' and from there 'Bulletin Archive' (not 'Selected Bulletin'). Insert 'December' and '2001' in the drop down menu and click 'Show Issue'.

In this activity we're looking at the 12/2001 (December 2001) report that (bizarrely) gives details of events in January 2002. Read the report as far as the fourth paragraph after Figure 12, and note particularly the spread of lava right through the town of Goma shown on the Figure 12 map.

Scroll down until you find the report dated 04/2002, and note in particular the Figure 15 map and the photographs that follow, especially Figure 21.

Now compose a single sentence to describe the location and nature of the sites where the lava flows originated.

Answer

I used information on the map (Figure 15) and the caption to Figure 21, to decide upon the following simple description: Lava was erupted via dykes that supplied magma from the central conduit to secondary vents low on the southern flank of the volcano. Your wording was probably different, but I hope you mentioned the terms I underlined. You may also have mentioned fissures or fissure eruption.

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