The Long Term Effects of Volcanic Eruptions

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Long-term effects of volcanic eruptions

Done by: Clare, Janice, Nadhirah, Nurul Dinie & Peng Ho

of

Temasek Academy, Temasek Junior College

Content Page

1. Introduction to Mount Pinatubo
        
 General information

         Long-term effects of Mount Pinatubo

         Literature Review

2. Introduction to Mauna Loa, Mount St. Helens, Krakatoa

         General information

         Long-term & immediate effects

         Literature Review

3. Comparison between the 3 volcanoes and Mount Pinatubo

         Which volcano will cause the most damage

4. Conclusion

         Why people should be concerned with the long-term effects of volcanoes

         What people can do about such effects

Introduction to Mount Pinatubo

Mount Pinatubo is located in Philippines, in the central area of the island of Luzon.  It is bordered by 3 provinces namely Pampanga, Zambales and Tarlac. It is part of the western volcano chain that extends more than 137 miles in a north south direction. The volcano began to be active approximately around 1.1 million years ago. It is a stratovolcano that comprises of numerous lava domes surrounded by layers and layers of pyroclastic material. The volcanic eruptions of Mount Pinatubo are separated by centuries of inactivity or quiescence. This allows dense tropical vegetation to grow around the volcano during these periods of quiescence. The eruptions are usually destructive, explosive and massive in size and involve the emission of large quantities of ash and pumice. Subsequently, this results in formation of lava domes.

Devastating eruption

In June 1991, after about 400 years of inactivity, Pinatubo produced one of the most massive explosions the world has ever seen. Before the major explosion, a series of minor explosions and earthquakes began on June 12. This series of minor events, which indicated an imminent explosion, ended on June 15. To be exact, at 10.27 am that morning, a Plinian column of gas (a vertically-directed ash column erupted from the newly formed horseshoe-shaped crater within minutes of the lateral blast), ash and pumice rose to a height of 40 km, producing a giant umbrella that extended over several hundred kilometers. The giant umbrella subsequently blackened the sky, raining pumice and ash over an area expanding over 300 thousand square kilometers. Several hours later, Mount Pinatubo produced a sequence of pyroclastic flows, devastating valleys located near the volcanoes and areas up to a distance of 15 kilometers. This massive eruption led to the formation of a caldera of 2km in diameter.

Why the immediate effects had minimal impact

Due to the series of minor explosions and earthquakes, scientists and researches were able to predict when Mount Pinatubo was going to erupt. Hence, they had the time and opportunity to evacuate the resident population of about 1.8 million people. Thus, despite the fact that the eruption was massive and highly destructive, the immediate effects on the population were small. The eruptions killed 833 people and injured 184. 23 were never found. Even so, most of the deaths, which in actuality occurred in the months after the eruptions, were the result of mudflows.

Long-term effects

The long-term effects can be classified into two categories -- economic losses and destruction of the environment. The economic losses were colossal. An estimated 651 thousand people were unemployed. Clark Airbase, one of the largest in the world, famous as a base of operation in the Vietnam War was rendered unusable and had to be abandoned. One of the most dramatic results of the eruptions was the massive movement of ash and pumice caused by typhoons in later years. Of the estimated 1.7 to 2.4 cubic miles of material accumulated on the slopes of the volcano, 70% has been swept away and carried downhill in the form of immense mudflows or lahars. These mudflows buried towns, knocked down power lines, swept away roads and caused more victims then the eruptions.

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Steps undertaken to mitigate effects

Over the months and years following the eruptions, artificial embankments have been built to prevent the flooding of inhabited and cultivated area. Decisive human efforts undertaken before, during and after the 1991 eruption reduced the loss of human life and mitigated the financial losses. Even so, the eruption caused an enormous disturbance in the geological balance of a vast area, a disturbance that will have effect on the inhabitants and the environment for many years to come.

Krakatau

Introduction to Krakatau

Krakatau is a volcanic island located ...

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