Using the choices below, select the statement that best explains how dissolved gases drive volcanic eruptions. A. Decreases in confining pressure result in decreasing viscosity of the magma, allowing the magma to ooze from the volcano. B. Confining pressure decreases on a rising magma, allowing gas bubbles to expand and fracture the magma. This process further decreases pressure on the magma and will result in an explosive event. C. As the magma rises, gas bubbles contract, fragmenting the material and expelling it from the vent. D. As the magma rises, gases reduce silicate mineral chains by breaking silicon-oxygen bonds; the result is an explosion.

 B. Confining pressure decreases on a rising magma, allowing gas bubbles to expand and fracture the magma. This process further decreases pressure on the magma and will result in an explosive event.

Explanation: The bubbles inside the magma are responsible for making it bubble to the surface of the earth crust and the explosion that follows. As magma rises to the surface of the earth, it absorbs gases and water vapor which forms bubbles in the magma. As the pressure decreases in the magma, it causes these bubbles to increase. When the rise of magma cannot keep up with he growth in the bubbles, there is an explosive eruption to the surface.  Compare this to shaking a Coca Cola bottle before opening it.

If the magma rise keeps us with the gas bubbles, the eruption is not explosive.

B.As the magma rises, gas bubbles contract, fragmenting the material and expelling it from the vent.

Explanation: