Question

Why does high magma viscosity increase the likelihood of an explosive eruption?

1. viscous magmas tend to have high concentrations of explosive chemicals like nitro glycerin
2. gases are not able to flow through and escape viscous magmas as easily as fluid magmas, allowing large pressure differences to develop between viscous magmas and their surroundings
3. higher viscosity magmas tend to be hotter than more fluid magmas, giving viscous magmas more energy for explosions
4. high viscosity magmas tend to have high concentrations of the element uranium, which
commonly undergoes nuclear fission as the magma nears the Earth's surface, leading to a nuclear explosion
5. no scientific explanation for this relationship has yet been found

Answer 1

High magma viscosity leads to potential explosive eruptions due to the buildup of trapped gases under pressure. Viscous magmas resist fluid flow, causing pressure to increase until the rock fractures, releasing energy explosively. Misconceptions about the presence of certain explosive chemicals or uranium are incorrect.

Step-by-step explanation:

High magma viscosity increases the likelihood of an explosive eruption because viscous magmas allow gas to accumulate under high pressure. When the pressure of the trapped gases exceeds the strength of the surrounding rocks, it results in a powerful explosive eruption. Viscous magmas are thicker and resist fluid flow, which means that volatile gases released by the magma, such as water vapor, carbon dioxide, and sulfur dioxide, cannot easily escape as they could in less viscous, more fluid magmas. Instead, these gases build up pressure until the magma fractures the rock above it, resulting in an explosive release of energy.

Another important point to note is that high viscosity in magmas is often associated with a high content of silica, which forms stronger chemical bonds and thus increases the magma's resistance to flow. The excess pressure from the trapped gases combined with the inability to flow easily leads to a dramatic increase in the potential for a large-scale, explosive volcanic event. This relationship between viscosity and eruptive style is a key concept in volcanology and helps scientists predict volcanic hazards.

However, common misconceptions should be clarified: viscous magmas do not tend to have higher concentrations of explosive chemicals like nitroglycerin nor do they contain significant concentrations of uranium that undergo nuclear fission as suggested in some of the options provided in the question. Such elements are unrelated to the explosiveness of volcanic eruptions.