How does viscosity of magma affect eruptive style?

CONTROLS ON EXPLOSIVITY The viscosity of the magma, however, is also an important factor in determining whether an eruption will be explosive or nonexplosive. A low-viscosity magma, like basalt, will allow the escaping gases to migrate rapidly through the magma and escape to the surface.

Does viscosity affect eruption style?

The properties of the magma inside a volcano affect how an eruption will play out. In particular, the viscosity of this molten rock is a major factor in influencing how hazardous an eruption could be for nearby communities.

What type of magma viscosity does a shield volcano have?

5.3. Shield volcanoes form when a centralized vent produces low-viscosity flows over a long period of time (Walker, 2000). Most commonly they comprise basaltic lavas, but higher silica peralkaline lavas may also be present (Fig. 38).

What eruption style do shield volcanoes have?

Eruption Types and Classification Most shield volcano eruptions are nonexplosive (effusive), usually 0-1 on the Volcanic Explosivity Index (VEI), typically in the Hawaiian eruptive style. These eruptions produce fluid lava flows and may produce fire-fountains.

Do shield volcanoes have high or low viscosity?

Shield volcanoes Where a volcano produces low viscosity, runny lava, it spreads far from the source and forms a volcano with gentle slopes: a shield volcano. Most shield volcanoes are formed from fluid, basaltic lava flows. Mauna Kea and Mauna Loa are shield volcanoes.

What factors affect volcanic eruptive style?

The style of eruption depends on a number of factors, including the magma chemistry and content, temperature, viscosity (how runny the magma is), volume and how much water and gas is in it, the presence of groundwater, and the plumbing of the volcano.

What is viscosity and how does it affect volcanic eruptions?

Part 2: Viscosity The higher viscosity fluid takes more force to stir. The higher the viscosity, the more force one has to exert on the straw to create a rising bubble in the fluid. The higher viscosity fluid also has bubbles that rise with more force and have more of an explosive effect upon reaching the surface.

What makes a shield volcano A shield volcano?

A shield volcano is a type of volcano named for its low profile, resembling a warrior’s shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano.

Why do shield volcanoes have thin lava?

It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano. Repeated eruptions result in the steady accumulation of broad sheets of lava, building up the shield volcano’s distinctive form.

Which volcanoes have high eruptive force?

Because they form in a system of underground conduits, stratovolcanoes may blow out the sides of the cone as well as the summit crater. Stratovolcanoes are considered the most violent.

Which type of volcano has the highest viscosity magma?

The magma that has the highest viscosity is rhyolitic magma.

What is viscosity in magma?

Viscosity of Magmas 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 is a volcanic eruption style?

Volcanic eruptions may fall into six major types: Icelandic, Hawaiian, Strombolian, Vulcanian, Pelean, and Plinian. Encyclopædia Britannica, Inc.

What factors affect the eruption style of a volcano?

How does a shield volcano generate magma?

Do shield volcanoes have explosive eruptions?

Whereas stratovolcanoes and lava domes are the product of highly viscous flows, and cinder cones are constructed of explosively eruptive tephra, shield volcanoes are the product of gentle effusive eruptions of highly fluid lavas that produce, over time, a broad, gently sloped eponymous “shield”.

What are the factors that affect volcanoes eruptive style?

What kind of magma produces violent 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.

How is viscosity related to a shield volcano?

Basaltic Lava Magma that has a lower viscosity and lower silica content produces the volcanic rock called basalt and forms shield volcanoes. These basalt lava flows are what we find erupting out of the Kilauea volcano today in Hawaii.

How does the composition and viscosity of lava flows differ between composite volcanoes and shield volcanoes?

How does the composition and viscosity of lava flows differ between composite volcanoes and shield volcanoes? Composite volcanoes are mostly formed from thick, viscous, andesitic composition lava whereas shield volcanoes are formed from runny, less viscous, basaltic composition lava.

What is the relationship between viscosity and volatile levels of magma?

Differences in viscosity and volatile levels have significant implications for the nature of volcanic eruptions. When magma is deep beneath the surface and under high pressure from the surrounding rocks, the gases remain dissolved. As magma approaches the surface, the pressure exerted on it decreases.

Why are Felsic magmas more viscous than other magmas?

First, as we’ve already discussed, felsic magmas tend to be more viscous because they have more silica, and hence more polymerization. Second, felsic magmas tend to have higher levels of volatiles; that is, components that behave as gases during volcanic eruptions.

How does the composition of magma change during eruption?

Eruption styles can be correspondingly variable. Figure 4.2.1 image description: Four processes that can affect the composition of magma stored in chambers. Loss of olivine or pyroxene (by crystal settling) makes the upper magma more felsic.

How many volatiles does a magma have?

Although there are many exceptions to this trend, mafic magmas typically have 1% to 3% volatiles, intermediate magmas have 3% to 4% volatiles, and felsic magmas have 4% to 7% volatiles.