FIGURE3 Predicting volcanic eruptions
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B
G
H
C
M
D
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I
K
E
A
L
A Geologists study records of past eruptions by examining flow patterns of mud, lava and ash. From these patterns they can draw danger maps that pinpoint dangerous areas. B Satellites monitor changes in gas emissions and in the shape of the volcano. Specialised equipment can also measure heat increases. C Seismographs can detect the small earthquakes caused by rising magma. These are linked by transmitters to computers so that scientists can quickly detect changes. D Sound-measuring equipment was used to accurately predict an eruption in Mexico in 2000. E In 1983, an attempt was made to divert a lava flow away from the towns of Rocco and Rogalna on Mount Etna in Italy. A channel was dug and barriers erected. The lava slowed and solidified before reaching the towns. F Samples of gas can be collected and analysed. An increase in the amount of sulphur dioxide (SO 2 ) may indicate that magma is moving upwards. G A rise in the temperature of a crater lake often precedes an eruption. H It has been suggested that explosives could be used to breach crater walls, sending lava away from towns. This was first tried in Hawai’i in 1935. I Helicopters have been used to drop concrete blocks in front of flowing lava. J As magma rises and collects in the magma chambers, the cone may bulge outwards, warning of possible eruptions. Sensitive tiltmeters on the ground and on satellites can detect this bulging. K Any bulging can also cause tiny cracks to appear. L Buildings in areas prone to ash eruptions should have steeply sloping roofs so ash does not accumulate. M In 1973, sea water was sprayed onto lava that was threatening a town in Iceland. The lava cooled quickly and solidified.
SkillBuilder discussion Geographical inquiry 1. Study FIGURE3 . List the different techniques that have been used to try to stop the flow of lava. 2. Which technique do you think is the most effective and why? 3. Outline the ways in which geologists try to predict volcanic eruptions.
410 Jacaranda Humanities Alive 8 Victorian Curriculum Third Edition
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