Why do silica-rich magmas create explosive eruptions?
As magma rises and pressure is released, gas bubbles (mainly of water vapor and carbon dioxide) form and expand rapidly, causing explosions. Magmas with high silica content tend to erupt violently, because they are viscious. They form volcanoes like Krakatau and Tambora in Indonesia, and Mount Rainier and Mount St.
Is high silica magma explosive?
Magmas with high silica content have a high viscosity (resistance to flow) and are generally more explosive when eruptions occur.
Does silica cause explosive eruptions?
Silica-Rich Magma Traps Explosive Gases Magma with a high silica content also tends to cause explosive eruptions. H. Silica-rich magma has a stiff consistency, so it flows slowly and tends to harden in a volcano's vents. As a result, it plugs the vent.
What makes magma more explosive?
More crystals in the magma enable more gas bubbles to form, and so they make an eruption more explosive. The rate at which pressure is reduced also affects the explosiveness. If magma moves slowly toward the surface, gases in the magma have more time to escape.
How does the silica content of magma affect how explosive an eruption is?
The silica content of the magma determines how thick the magma is, how easily it flows and how easily dissolved gases within the magma can escape; therefore the silica content determines the characteristic of the volcanic eruption and the shape and size of the resulting volcanic cone.
How do explosive eruptions occur?
Explosive eruptions occur where cooler, more viscous magmas (such as andesite) reach the surface. Dissolved gases cannot escape as easily, so pressure may build up until gas explosions blast rock and lava fragments into the air! Lava flows are much more thick and sticky so do not flow downhill as easily.
Which magma lava type produces the most explosive eruptions?
Explosive eruptions are favored by high gas content & high viscosity magmas (andesitic to rhyolitic magmas).
Which of these magmas produce the most explosive eruptions?
The largest and most violent of all the types of volcanic eruptions are Plinian eruptions. They are caused by the fragmentation of gassy magma and are usually associated with very viscous magmas (dacite and rhyolite).
Which type of magma is most explosive?
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. These solid particles become pyroclasts or volcanic ash.
What silica content and viscosity are associated with explosive volcanoes?
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.
What is the most explosive type of magma?
Lavas and pyroclastics are usually andesitic to rhyolitic in composition. Due to the higher viscosity of magmas erupted from these volcanoes, they are usually more explosive than shield volcanoes.
Do explosive eruptions have silica rich and felsic magma?
Silica-rich, felsic magma can trap a lot of gas. So these magmas produce explosive eruptions.
Why does silica increase viscosity?
Temperature: The hotter the lava, the lower the viscosity (the thinner it is). The cooler the lava, the higher the viscosity (the thicker it is). Composition: he more felsic the lava (the more silica in the lava), the higher the viscosity because silica forms chains in the cooling lava even before it crystallizes.
Which lava type is the most explosive?
A Plinian eruption is the most explosive of the eruption types.
Which type of magma is the least explosive?
basaltic magma The least explosive type of volcano is called a basalt plateau. These volcanoes produce a very fluid basaltic magma with horizontal flows. The form of these volcanoes is flat to gently sloping and they can occupy an area from 100,000 to 1,000,000 square kilometers.
What magma types produce explosive and effusive eruptions?
Overview. There are two major groupings of eruptions: effusive and explosive. Effusive eruption differs from explosive eruption, wherein magma is violently fragmented and rapidly expelled from a volcano. Effusive eruptions are most common in basaltic magmas, but they also occur in intermediate and felsic magmas.
Which type of magma will produce the most explosive volcanic eruption?
andesitic to rhyolitic magmas 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.
Why is felsic lava more explosive?
Felsic lavas are not as hot, high in silica and volatiles, and have a high viscosity. They are thick and gooey and resist flowing. Their high volatile content makes them potentially highly explosive.
How does silica affect viscosity of magma?
The amount of silica in magma helps to determine its viscosity. The more silica magma contains the higher its viscosity. Magma that is high in silica produces light-colored lava that is too sticky to flow very far ex. … Low-silica magma flows readily and produces dark-colored lava ex.
Which magma produces the most explosive eruptions?
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. These solid particles become pyroclasts or volcanic ash.
Which magma type erupts most violently?
A Plinian eruption is the most explosive of the eruption types.
What type of lava is explosive?
Explosive eruptions generally involve magma that is more viscous and has a higher gas content. Such magma is often shattered into pyroclastic fragments by explosive gas expansion during an eruption. Volcanic eruptions may fall into six major types: Icelandic, Hawaiian, Strombolian, Vulcanian, Pelean, and Plinian.
Which is the most explosive type of volcanic eruption Why?
Plinian Eruption The largest and most violent of all the types of volcanic eruptions are Plinian eruptions. They are caused by the fragmentation of gassy magma, and are usually associated with very viscous magmas (dacite and rhyolite).
Why are felsic magma more explosive than mafic magma?
Gases – At depth in the Earth nearly all magmas contain gas. Gas gives magmas their explosive character, because the gas expands as pressure is reduced. Felsic magmas usually have higher gas contents than mafic magmas.
What type of lava is the most explosive?
A Plinian eruption is the most explosive of the eruption types.
Which type of volcanic eruption is very explosive?
Phreatic eruptions pulverise surrounding rocks and can produce ash, but do not include new magma. An eruption resulting from the interaction of new magma or lava with water and can be very explosive.
Why are felsic volcanoes more explosive?
Felsic lavas are not as hot, high in silica and volatiles, and have a high viscosity. They are thick and gooey and resist flowing. Their high volatile content makes them potentially highly explosive.
What type of magma would probably cause the most explosive eruption?
Rhyolitic magma would probably cause the most explosive eruption.