Geology Chapter 5
Review questions 1-10
Pages 146-147
1. Describe the three different kinds of material that can erupt from a volcano.
Products of eruption come in three forms; lave flow, which can be Basaltic, Andesitic or Rhyolitic lava. A volcano also erupts pyroclastic debris (when lava flies into the air and freezes) and gases.
2. Contrast a pyroclastic flow with a lahar.
Pyroglastic debris are blasting clots of lava, and the lahar are like mudslides that can reach up to 50km per hour. When the lahar stops moving it creates a layer of volcanic depris, (which can contribute to the pryroclastic debris).
3. Describe the differences among shield volcanoes, strato- volcanoes, and cinder cones. How are these differences explained by the composition of their lavas and other factors?
Shield volcanoes form when the products of eruption have low viscosity and are weak, so they do not pile up but spread. They are broad, gentle does that resemble a solder’s shield. Cinder cones are cone shaped piles of basaltic lapilli and blocks. Strato-volcanoes are large; cone shaped and is made of interleaved layers of lava, tephra and volcaniclatic debris. The prefix of its name emphasizes that they can grow to be kilometers high.
4. Why do some volcanic eruptions consist mostly of lava flows, while others are explosive and do not produce flows?
Eruption style depends on the viscosity and the gas content of the magma.
An effusive eruption occurs when the magma feeding the volcano is hot and mafic causing it to have low viscosity. An explosive eruption occurs when pressure builds in a volcano. It may be a small explosion like a basaltic eruption where the gas builds up and suddenly escapes or it can be a large explosion which can be triggered by many things, such as cracks in the flank of an island volcano where water enters the magma chamber and turns to steam, or if a very viscous magma plugs the vent and the pressure increases so much it cracks parts of the volcano and
Pages 146-147
1. Describe the three different kinds of material that can erupt from a volcano.
Products of eruption come in three forms; lave flow, which can be Basaltic, Andesitic or Rhyolitic lava. A volcano also erupts pyroclastic debris (when lava flies into the air and freezes) and gases.
2. Contrast a pyroclastic flow with a lahar.
Pyroglastic debris are blasting clots of lava, and the lahar are like mudslides that can reach up to 50km per hour. When the lahar stops moving it creates a layer of volcanic depris, (which can contribute to the pryroclastic debris).
3. Describe the differences among shield volcanoes, strato- volcanoes, and cinder cones. How are these differences explained by the composition of their lavas and other factors?
Shield volcanoes form when the products of eruption have low viscosity and are weak, so they do not pile up but spread. They are broad, gentle does that resemble a solder’s shield. Cinder cones are cone shaped piles of basaltic lapilli and blocks. Strato-volcanoes are large; cone shaped and is made of interleaved layers of lava, tephra and volcaniclatic debris. The prefix of its name emphasizes that they can grow to be kilometers high.
4. Why do some volcanic eruptions consist mostly of lava flows, while others are explosive and do not produce flows?
Eruption style depends on the viscosity and the gas content of the magma.
An effusive eruption occurs when the magma feeding the volcano is hot and mafic causing it to have low viscosity. An explosive eruption occurs when pressure builds in a volcano. It may be a small explosion like a basaltic eruption where the gas builds up and suddenly escapes or it can be a large explosion which can be triggered by many things, such as cracks in the flank of an island volcano where water enters the magma chamber and turns to steam, or if a very viscous magma plugs the vent and the pressure increases so much it cracks parts of the volcano and