Sunday, January 29, 2012

Tackling Volcano Exam Questions (2)

Volcano Sample Question (2)

Explain why some volcanic eruptions are more violent than others. (4 marks)

Command Word: Explain
Key Words: Volcanic eruptions, more violent, others


What factors make volcanoes more violent?
-Type of plate boundary? (Destructive)
-Type of volcano? (Composite)
-Type of lava (Acidic lava, more viscous lava)
-Amount Of gases (A higher amount of gas, the lava becomes under higher pressure)
-Eruption Frequency? (long dormant periods, irregular eruptions)

Ans: There are certain factors that make volcanoes more violent than others. Firstly, the type of plate boundary it’s on makes the difference. A more gentle volcano rests on a constructive plate, where the plates move apart and lava oozes out, a more violent volcano rests on a destructive boundary, where one crust is subducted under the under and is destroyed under high heat and pressure.

The type of lava also plays a role, a gentle volcanic eruptions tends to erupt basic lava that contains less silica while a more violent volcano erupts acidic lava, which has a higher silica content making it more explosive. Next, the volcano type determines it’s violence level. A shield volcano such as Mount Loa tends to be more gentle and causes little to no impact to humans while a composite volcano for example Montserrat is more destructive and causes large impacts to humans.

Not only that, the amount of gases in the lava also plays a role, a lower concentration of gases ensures that the magma is under low pressure making the eruption gentle while a high concentration of gases causes the magma to be under higher pressure causing the eruptions to become more violent. Lastly, the volcano eruption frequency also plays a important role, a volcano that eruptions frequently makes the volcano more gentle as the pressure does not build up in the volcano while a volcano that have long dormant periods and irregular eruption frequency causes a “plug” to form on the mouth of the volcano thus pressure builds causing a more violent eruption

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