What is the difference between low gas low viscosity eruptions compared to a height viscosity and high gas eruptions?

Answer 1

Low gas and low viscosity versus high gas and high viscosity eruptions are characterized by completely different types of eruption.

The low gas and low viscosity eruption would be a Hawaiian type of eruption, were the lava free flows from the ground down slope often at the pace of a brisk walk. The lava flows are very hot and destructive, however donot normally result in loss of life, as the flows are rather slow moving and non-explosive. The type of magma that would cause this type of eruption is basalt, and would create a mountain similar to Mauna Loa and Kilauea on the big island of Hawaii.

A high gas and high visocisty eruption would often times be very explosive as the gasses inside the volcano would be trapped until the pressure would be enough to overcome the force of the volcano holding it inside. This would often times result in a highly explosive eruption as the minute that gas would be released the dissolved gasses inside the magma would begin to fall out of solution and create large bubbles raising the pressure even further in the magma chamber. The type of magma that would cause these high power eruptions would be Rhyolite. Rhyolite is very resistant to flow and readily traps gasses within it in the process. Examples of volcanoes that produce these types of eruptions would be Krakatau in Indonesia, as well as Mt. St. Helens in Washington.