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In Colombia, more than 23 000 people died in 1985 when the Nevada del Ruiz volcano erupted.
The heat from the eruption melted huge quantities of snow and ice on the top of the volcano.
This mixed with volcanic ash and fl owed downhill as lahars (mud fl ows), which wiped out the town of Armero. There had been small earthquakes and emissions of gas for about a year before the eruption. Two scientists were sent to monitor the volcano, but they were short of equipment and it took a long time for them to get their data analysed. The US Geological Survey (USGS) was prepared to send a couple of experts to assess the danger, but fi ghting in other parts of Colombia led to a travel ban for US government employees, and so they did not go.
The Colombian scientists warned that the volcano could erupt, but they could not predict exactly when it would do so. Local offi cials were not convinced. Even though there were maps showing the likely risk areas, and Armero itself was built on the remains of a mudfl ow that had occurred
140 years before, no one was evacuated.
Less than a year after this eruption, the USGS set up a team of geologists and equipment that could be fl own anywhere in the world where a volcano might become a danger.
These scientists were fl own to the Philippine Islands in 1991, when Mount Pinatubo began to show signs that it might erupt. They worked with local scientists to set up monitoring equipment and map out the areas at greatest risk. Careful analysis of their instruments allowed them to give daily updates about the likely risk of an eruption. Evacuation of the area around the volcano started about a week before the eventual eruption, and evacuation from a wider area started the day before. In all, over 60 000 people were moved. In the end, only about 300 people died, most of these from buildings collapsing under the weight of ash ejected from the volcano.
The US government has an air base less than 25 km from Mount Pinatubo, so they had a special interest in ensuring the best predictions possible of an eruption. However the USGS sends its teams of experts to assist in other places as well, and they have built up a great deal of experience in predicting eruptions and possible dangers.
1 Why is it important that the warning of an eruption is not given a too early b too late?
2 a Suggest why it is important to know something about the history of a volcano if there is a danger it might erupt again.
b How could this information be obtained? c How accurate is this information likely to be?
3 a Why do scientists need to collaborate with local government offi cials if a volcano is likely to erupt?
b Suggest why the local government offi cials in the Philippines were likely to take more notice of the scientists than the Colombian offi cials.
4 The USGS is paid for by the US government, and so is ultimately paid for by US taxpayers. a Why do you think the US government sent scientists to the Philippines to assess
Mount Pinatubo?
b Why do you think they send USGS scientists to other countries?
5 Many people live on Hawaii. The active volcanoes on Hawaii produce runny lava.
Volcanoes such as Mount Pinatubo, Mount
Vesuvius or Nevado del Ruiz usually explode and shoot out large quantities of ash.
Suggest why it is safer to live near the
Hawaiian volcanoes than near volcanoes such as Mount Pinatubo.
I CAN...
• extract relevant information from a text
• discuss the ways in which scientists and governments need to collaborate for public safety.
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