Volcanic Activity and Magma Formation

Which are needed in the formation of magma?

• composition, pressure, temperature

• composition, pressure, density

• pressure, temperature, distance from the surface

• pressure, temperature, volume

If a volcano's magma is high in silica, how will you describe to its volcanic activity?

• It will erupt quietly

• It will remain dormant

• It will erupt explosively

• It will produce dark-colored lava

Viscosity is a measure of a material's resistance to flow. Which DOES NOT affect the viscosity of magma?

• location of magma

• temperature of the magma

• chemical composition of the magma

• presence of dissolved gases in the magma

Which is TRUE about the composition of magma?

• It contains ash, dust, and lava

• It contains dissolved gases only.

• It contains fragmented rocks only.

• It contains both dissolved gases and fragmented materials.

Several kilometers from a volcano, a geologist observes an old lava flow made up of dark-colored basalt rock. The geologist infers that the lava must have had____________.

• low viscosity

• high viscosity

• medium viscosity

• high silica content

Which type of lava will offer the least resistance to flow?

• Andesitic

• Basaltic

• Rhyolitic

• Basaltic and Rhyolitic

The magma in the chamber of a volcano has a very high amount of silica. If the volcano would erupt, which might happen?

• The lava would flow very slowly

• The volcano would erupt violently

• The volcano would erupt non-explosively

• There would be a build-up of pressure below the crater

Which is NOT a common gas in magma?

• methane gas

• carbon dioxide

• sulfur dioxide

• water vapor

When compared to andesitic lavas, what characteristics of basaltic lavas will be shown?

• lower in viscosity and it retains dissolved gases.

• higher in viscosity and it retains dissolved gases.

• lower in viscosity and it easily releases dissolved gases.

• higher in viscosity but it easily releases dissolved gases.

Water vapor is one of the dissolved gases released by erupting volcano. It is present in large amounts, and is considered harmless. When will it become harmful to the living things and environment?

• when it is in the lower atmosphere

• when it is in the middle atmosphere

• when it is in the upper atmosphere

• when it combines with other dissolved gases