Convergent Plate Tectonic Hazards - Earthquakes.

by munirs220isgedusa (student)

Explain the tectonic hazards that may occur at convergent plate margins. For one type of tectonic hazard, evaluate its impact on lives and property. [15]

At convergent or destructive plate boundaries an oceanic plate and continental plate are moving towards each other. The oceanic plate composed largely of basalt will subduct beneath the continental crust. As the oceanic lithosphere descends the increase in pressure will trigger major earthquakes along the Benioff zones. In addition, the dehydration of the subducted oceanic crust caused by an increase in pressure results in the release of magma into the overlying mantle which promotes partial melting and the generation of new magma. The new magma, being less dense than the surrounding the mantle will rise to the Earth's surface, and Strato-volcanoes will form. The eruption of Strato-volcanoes are violent and result in the release of lava, volcanic bombs, and pyroclastic flows, and will result in secondary hazards in the form of lahars, potentially tsunamis, and acid rainfall.

Earthquakes are a tectonic hazard which undeniably causes significant damage to both lives and property. Ground shaking is the most prominent effect of earthquakes, however, while earthquakes cause significant casualties these casualties are not caused directly by the ground movement, it is instead the secondary hazards that result in significant loss of life and property. Liquefaction and subsidence of ground movement are more important effects of earthquakes which creates greater damage. Liquefaction is when solid sediments are turned to fluids as a result of P-waves (pressure waves) generated from an earthquake. The 1964 Niigata earthquake resulted in three apartment ...

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The more hazardous effects of earthquakes include landslides and fires. Landslides can cause significant damage to both lives and property, this is evident by the Ancash or Great Peruvian earthquake (May 1970) that triggered massive landslides and resulted in approximately 70,000 deaths. The most destructive landslide fell from Peru’s highest mountain, Mount Huascaran. The landslide swallowed most of the village of Yungay, and annihilated much of Ranrahrica, resulting in over 18,000 deaths. However, landslides are often localised and therefore the damage they create is less widespread. In contrast, fires are more common during earthquakes and spread rapidly, resulting in significant damage. The 1923 Kanto earthquake in Japan resulted in nearly 100,000 deaths, over 70,000 which were caused by fires that swept through Tokyo. However, fires that occur today can be better managed, and gas and electrical pipes can be turned off as to prevent fires from occurring in the first place. Therefore landslides and fires although dangerous, are not the most hazardous impact of earthquakes.

The most devastating impact of earthquakes, causing widespread and significant damage, are tsunamis. Tsunamis are a series of ‘harbour waves’ caused when the seafloor moves vertically in an earthquake. The most destructive tsunami was triggered by a 9.1 magnitude earthquake off the coast of the Indonesian island of Sumatra. This generated a series of large tsunami waves that reached out across the Indian Ocean and hit the coasts of Indonesia, Sri Lanka, India, Maldives and Thailand sustaining massive damage, resulting in the death of 225,000 people. The 2004 Indian Ocean tsunami was one of the deadliest natural disasters in recorded history and demonstrates that tsunamis are the most destructive hazard caused by earthquakes.

In conclusion, earthquakes can result in serious damage to both lives and property. The most familiar effect of earthquakes is ground shaking however the secondary hazards of earthquakes create more damage. The secondary hazards of earthquakes include liquefaction, landslides, fires and tsunamis, in general, each of these factors causes serious damage, however, the most devastating impact is caused by tsunamis largely because its effects are more widespread and because it is not possible to manage or prevent the dangers of a tsunami, whereas fires and landslides can to some extent be controlled.