2. How did the humans protect and prepare themselves?
On July 16, 1990, an earthquake of magnitude 7.8 struck central Luzon. The epicentre was about 100 kilometres northeast of Pinatubo. This may have been the cause of the eruption in 1991. However, it’s impossible to prove this hypothesis. Two weeks after the eruption, the local residents reported steam coming from the volcano. But scientists concluded that landslides were the cause of this steam and eruptive activity didn't have anything to do with it.
On March 15, 1991, the villagers felt a series of earthquakes at the north western side of the volcano. Two weeks after that more earthquakes were felt and it became clear that volcanic activity was likely. On April 2, the volcano awoke.
The next few weeks there were several small eruptions. The surrounding areas became covered with volcanic ash. Seismographs recorded hundreds of small earthquakes every day.
The volcanic activity increased throughout April and May. The first eruption with magma was on June 3, and the first large explosion on June 7. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) issued a warning about a possible major eruption within two weeks.
All the signs of anvery large eruption were given. PHIVOLCS and U.S. Geological Survey tried to convince the local people of the severity of the situation. But a false warning could lead to cynicism about warnings in the future and a late warning could lead to thousands of deaths.
Three evacuation zones were defined each within 40 km of the volcano’s summit. These three zones together had a total population of about 371.000 people.
They also defined five stages of volcanic alert from 1 (low level seismic disturbances) to 5 (major eruption in progress). Daily alerts were issued in local newspapers and on radio and television stations, here you could find the alert level and the associated danger area.
Many of the people who lived on the slopes of the volcano left their villages when the eruption began in April. The first formal evacuation was ordered on April 7 in the 10 km zone. The second evacuation was the one of the 10-20 km zone on June 7. On June 13, the 20-40 km zone had to be evacuated when a level 5 alert was issued.
So the people living near the volcano had quite some time to prepare themselves and evacuate people who were in danger.
On March 15, 1991, the villagers felt a series of earthquakes at the north western side of the volcano. Two weeks after that more earthquakes were felt and it became clear that volcanic activity was likely. On April 2, the volcano awoke.
The next few weeks there were several small eruptions. The surrounding areas became covered with volcanic ash. Seismographs recorded hundreds of small earthquakes every day.
The volcanic activity increased throughout April and May. The first eruption with magma was on June 3, and the first large explosion on June 7. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) issued a warning about a possible major eruption within two weeks.
All the signs of anvery large eruption were given. PHIVOLCS and U.S. Geological Survey tried to convince the local people of the severity of the situation. But a false warning could lead to cynicism about warnings in the future and a late warning could lead to thousands of deaths.
Three evacuation zones were defined each within 40 km of the volcano’s summit. These three zones together had a total population of about 371.000 people.
They also defined five stages of volcanic alert from 1 (low level seismic disturbances) to 5 (major eruption in progress). Daily alerts were issued in local newspapers and on radio and television stations, here you could find the alert level and the associated danger area.
Many of the people who lived on the slopes of the volcano left their villages when the eruption began in April. The first formal evacuation was ordered on April 7 in the 10 km zone. The second evacuation was the one of the 10-20 km zone on June 7. On June 13, the 20-40 km zone had to be evacuated when a level 5 alert was issued.
So the people living near the volcano had quite some time to prepare themselves and evacuate people who were in danger.