How does high-viscosity magma affect an eruption's explosiveness?

Explosivity of volcanic eruptions. Of lava flows on the earth's surface. Above the volcano.

(molten rock) underlying the volcano. And the amount of dissolved gases in the magma. (Na), potassium (K), and phosphorous (P).

Relatively high silica and low Fe and Mg contents. Crystallize to produce the rock andesite. Colored than the felsic rock types.

Of a substance is a measure of its consistency. As the ability of a substance to resist flow. Is the inverse of fluidity.

Has a higher viscosity than water because it is less fluid. The effect of temperature on viscosity is intuitive. Becomes, thus lowering its viscosity.

A magma's viscosity. Of chemical bonds within the liquid. And cations, respectively).

Found in magmas (see above), oxygen is the only anion. On the other hand, is the most abundant cation. Of a magma's viscosity.

In its liquid state (i.e. The crystallization temperature of magma). Is in the shape of a tetrahedron.

Silicon-oxygen tetrahedra, as shown here. Share electrons with the outer oxygen atoms of other tetrahedra. Of covalent bonds between tetrahedra.

Of tetrahedra, and complicated networks of tetrahedra. Leads to the development of crystals within the liquid medium. Silicate minerals found in all igneous rocks.

Than those with low-silica contents. Way than temperature and silica content. Viscosity is variable.

As gas escapes. Mixture depends on both the size and distribution of the bubbles. The driving force for the eruption.

From the magma, bubbles will begin to form. Or gas exsolution. Dissolved gases and the temperature of the magma.

Increases the vapor pressure. Bubbles when the cap is removed. As the first boiling.

The residual liquid will become increasingly enriched in gas. Can also lead to gas exsolution. As second (or retrograde) boiling.

Can trigger an explosive volcanic eruption. To the surface. Explosively from the volcano.

Magmas which have high viscosities and high gas contents. Explosively in the presence of groundwater or surface water. More information on the variability of explosivity, see the Volcano Explosivity Index.

Click image to download. Viscosity for Windows. Magmas from the magma composition and temperature.

Magma for Windows. Magma composition and temperature.