Table of Contents
- 1 How the presence of silica and water in magma increases the chances of an explosive eruption?
- 2 Does silica make volcanoes more explosive?
- 3 Which type of magma would cause a more explosive eruption?
- 4 How does silica content affect the viscosity of magma?
- 5 What happens if magma has high silica?
- 6 What two factors control the explosiveness of an eruption?
- 7 Why does water make volcanoes more explosive?
How the presence of silica and water in magma increases the chances of an explosive eruption?
Explain how the presence of silicon or water in magma increases the chances of an explosive eruption. Both water and silicon increase the pressure that build up in the volcano. The water because it makes vapor and the silicon because it moves so slowly. What is a pyroclastic flow?
Does silica make volcanoes more explosive?
Silica: Influences lava viscosity and overall shape of the volcano. Silica molecules form a strong bond that permits entrapment of volcanic gases and promotes explosive volcanic eruptions. Low-silican magmas allow rapid escape of gases and low-explosivity eruptions.
What increases the explosive potential of magma?
The amount of dissolved gas in the magma provides the driving force for explosive eruptions. The viscosity of the magma, however, is also an important factor in determining whether an eruption will be explosive or nonexplosive.
Which type of magma would cause a more explosive eruption?
Explosive eruptions are favored by high gas content & high viscosity magmas (andesitic to rhyolitic magmas). The explosive bursting of bubbles fragments the magma into clots of liquid that cool as they fall through the air.
How does silica content affect the viscosity of magma?
Viscosity is the resistance to flow (opposite of fluidity). Viscosity depends on primarily on the composition of the magma, and temperature. Higher SiO2 (silica) content magmas have higher viscosity than lower SiO2 content magmas (viscosity increases with increasing SiO2 concentration in the magma).
What effect does water have on the viscosity of magma?
The magma slows down. WATER CONTENT is inversely related to viscosity. The higher the water content, as a liquid, the lower the viscosity. Water in the mantle causes it to melt faster and creates magma with a higher flow rate.
What happens if magma has high silica?
Lava with high silica content is thick and viscous and does not readily flow. Lava rises up toward the surface but is too thick to squeeze through the cracks and fissures in the Earth. At this point the lava will explode outward much as champagne from a bottle when the cork is released.
What two factors control the explosiveness of an eruption?
Volcanoes
| Question | Answer |
|---|---|
| These two factors control whether an eruption will be explosive or quiet? | Water vapor and silica |
| Magma that is low in silica and produces nonexplosive eruptions is called? | basaltic |
| Magma that is high in silica and produces explosive eruptions is called? | granitic |
How does the silica content affect the behavior of the magma?
A more viscous (thick) magma will produce a more violent eruption This is controlled in part by the concentration of silica in the magma. A magma with low silica (<45%) will be runny and so the eruption will not be explosive. A magma with high silica (>60%) will be quite viscous and so the eruption will be violent.
Why does water make volcanoes more explosive?
Water-rich magmas contain volatiles, which increase the melt’s buoyancy and drive its ascent. Water is particularly effective at driving the upward movement of magma because it comes out of solution at a range of pressures. “Those volatiles will act as hot air balloons and drag the magma upwards,” said Cassidy.