Why Is Silica Rich Magma Explosive


Why Is Silica Rich Magma Explosive?

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. … If enough pressure builds up an explosive eruption takes place.

Why does silica make magma more explosive?

Magmas with higher silica concentration are more viscous and thus move slower than magmas with less silica. … More crystals in the magma enable more gas bubbles to form and so they make an eruption more explosive.

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. All magmas also contain some degree of trapped gasses (CO2 & H2O ). The more trapped gas the more violent the explosion.

What makes magma so explosive?

When magma is rapidly expelled from a volcano it undergoes rapid cooling. This induces the formation of crystals resulting in a sudden increase in the viscosity of the magma. In turn this produces magma fragmentation creating a highly explosive eruption. Dr.

Does high 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 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.

Which magma is the most explosive?

Explosive eruptions are favored by high gas content & high viscosity magmas (andesitic to rhyolitic magmas).

What characteristics of magma determines its explosiveness?

Viscosity together with the amount of gas dissolved in magma can determine the explosivity of the eruption. More viscous magma with volatiles is more explosive than less viscous magma where gases can bubble out relatively easily.

What two factors control the explosiveness of an eruption?

The amount of water vapor and other gases present is one factor that determines whether a volcanic eruption will be quiet or explosive.

What type of eruption is the most explosive?

Plinian eruption

A Plinian eruption is the most explosive of the eruption types. Mt. St. Helens eruption was a plinian eruption.

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Why do explosive volcanoes 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! … These eruptions build up more steeply-sloping Composite volcanoes like this one in Chile.

How does lava explode?

As the magma rises bubbles of gas form inside it. Runny magma erupts through openings or vents in the earth’s crust before flowing onto its surface as lava. If magma is thick gas bubbles cannot easily escape and pressure builds up as the magma rises. … this can build up enough pressure to cause an explosion.

What makes a volcanic eruption explosive or nonexplosive?

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.

How does silica get into magma?

Silicate-rich magmas are typically formed at destructive plate boundaries by partial melting and/or assimilation of crustal rocks (which are richer in silica than the rock of the mantle).

What is the relationship between the silica content of magma and the explosiveness of volcanic eruption?

What is the relationship between the silica content of magma and the explosiveness of a volcanic eruption? The more silica the larger the explosion.

How does magma viscosity influence the explosive potential?

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 low silica (<45%) will be runny and so the eruption will not be explosive.

Where are silica rich volcanoes?

It forms broad shield volcanoes such as the island of Hawaii which erupts large quantities of lava. On the other hand volcanoes that form from silica rich magma tend to be steep and tall such as Mount St. Helens in Washington.

Which magma has the highest silica content?

As a result of its higher viscosity and gas content intermediate magma builds up pressure below the Earth’s surface before it can be released as lava. Felsic magma has the highest silica content of all magma types between 65-70%. Thick viscous felsic magma can trap gas bubbles in a volcano’s magma chamber.

What does it mean by higher silica content magma in terms of viscosity?

The higher the amount of silica in the magma the higher is its viscosity. Viscosity is a liquid’s resistance to flow. Viscosity determines what the magma will do. Mafic magma is not viscous and will flow easily to the surface. Felsic magma is viscous and does not flow easily.

Why are some eruptions explosive and some effusive?

Volcanic eruptions can be explosive sending ash gas and lava high up into the atmosphere or the magma can form lava flows known as effusive eruptions. Whether an eruption is explosive or effusive largely depends upon the amount of gas in the magma.

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Why is magma called lava after eruption?

Magma comes from an Italian word that means a thick pasty substance which is how molten rock behaves within the Earth. Lava another Italian word means to slide which is what molten rock does once it reaches the surface.

Which volcano type is the most explosive due to high gas and silica content in their lava?

Composite volcanoes are some of the most dangerous volcanoes on the planet. They tend to occur along oceanic-to-oceanic or oceanic-to-continental boundaries because of subduction zones. They tend to be made of felsic to intermediate rock and the viscosity of the lava means that eruptions tend to be explosive.

How does magma composition affect volcanic eruption?

Magmas differ in composition which affects viscosity. Magma composition has a large effect on how a volcano erupts. Felsic lavas are more viscous and erupt explosively or do not erupt. Mafic lavas are less viscous and erupt effusively.

Which characteristics of magma does not determine its explosiveness?

Non explosive eruptions are favored by low gas content and low viscosity magmas (basaltic to andesitic magmas). If the viscosity is low non-explosive eruptions usually begin with fire fountains due to release of dissolved gases. When magma reaches the surface of the earth it is called lava.

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.

Where do explosive eruptions occur?

Most explosive eruptions occur in volcanoes above subduction zones where one tectonic plate dives beneath the other. Eighty to 120 kilometers below the surface magma forms when the rocks of the mantle melt just above the subducting plate.

Why are silicic volcanoes explosive?

Eruptions will be effusive if the magma has a low ascent velocity. At higher magma ascent rates the fragmentation within the magma passes a threshold and results in explosive eruptions. Silicic magma also exhibits this transition between effusive and explosive eruptions but the fragmentation mechanism differs.

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What kind of volcanic eruption is least explosive?

Shield volcanoes

Shield volcanoes tend to be the least explosive volcanoes.

Was Mt Everest a volcano?

Mount Everest is not an active volcano. It is not a volcano but a folded mountain formed at the point of contact between the Indian and Eurasian…

Which magma composition causes the most violent volcanic eruptions?

Which magma composition causes the most violent volcanic eruption and why? 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 does water make volcanoes more explosive?

Water migrates upwards and causes the top of the subducted oceanic crust to melt producing magma beneath the Cascade volcanoes. The key part of the study Wallace said involved hydrogen isotopes. “Most of the hydrogen in water contains a single proton ” he said.

When a volcano ejects lava explosive the eruption is called?

Phreatic eruptions pulverise surrounding rocks and can produce ash but do not include new magma. Phreatomagmatic eruption. An eruption resulting from the interaction of new magma or lava with water and can be very explosive.

Why do some volcanoes explode video?

What is the main danger to people during explosive volcanic eruptions?

Volcanic ash can make breathing difficult and can cause buildings and structures to collapse (especially when the ash is wet) damage agricultural crops and contaminate grass used for livestock feed. The downwind ash plume from such eruptions also poses a hazard to aircraft.

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