Natural Disaters

Volcano Case Histories: Killer Events

Chapter 9

p. 217-244

1. A) What type of eruption is typical of Iceland?

1. The most typical Icelandic eruptions are fissure eruptions, where lava pours out of long fractures.

B) What 3 things did Icelanders do to “control” the lava flows on Heimaey?

1. Pyroclastic material was bulldozed to create barriers that diverted and controlled the flow of later lavas and controlled the flow paths of the dense volcanic gases. The Icelanders also sprayed seawater on the lave flows causing rapid cooling and hardening into wall like features that forced lava to flow in another direction.

2. What events created the jokulhlaup in 1996?

2. An earthquake began in southeastern Iceland on September 30th 1996 as fissuring opened along the mid Atlantic spreading center beneath the thick Vatnajokull glacier which covers 10% of Iceland. In two days magma rising through the fissure melted through the 600m thick ice cap sending steam and other gases several kilometers into the atmosphere. On November 5th the rising water lifted up the glacier and poured forth an enormous jokulhlaup.

3. Of all the Cascade mountain volcanoes – which has gone the longest time without an eruption? (use a figure to answer this question – there will be more than one volcano)

1. Mount Garibaldi, Mount Adams, Mount Jefferson, Crater Lake and Mount McLaughlin all have not erupted for over 4000 years.

4. A) When did Lassen Peak erupt last?

3. On May 22, 1915

B) If you are terrified of the possibility of a volcanic eruption would it be wise to live on the lower slopes of Mt. Shasta? Why or why not?

1.No The lower slopes of Mount Shasta ate broad and smooth, allowing pyroclastic flows to spread widely as they move down the volcano flank.

5. A) What are the differences between a lahar and a pyroclastic flow?

B) List the 4 ways pyroclastic flows can be created and give an example of each.

4. Lahar flow is a...