Why is a non viscous volcano less dangerous than a volcano with viscous lava?

Question

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Answer 1

High viscous lava is more dangerous because viscosity is a manifistation of Surface tension , a liquid more viscous can hold gas to a larger extent then a less viscous fluid, hence though a high viscous lav , though it would move slowly but in its interior it will carry lot of gas and energy, hence while after a initial build up when volcano will erupt it will throw the lava much higher and shell cover a wider area then low viscocity lava which will tend to flow on slope.

Answer 2

Viscous Lava

Answer 3

All the previous answers lacked one word: Caldera. Viscous volcanoes (rhyolite volcanoes, for example) tend to block up the outlet, thus allowing pressure to build up inside the volcano. When the pressure exerted exceeds the ability of the viscous lava cap to contain it, a massive explosion occurs, obliterating everything within the near (and sometimes relatively far) area. Although Mount St. Helens was a composite volcano, when it exploded in 1980 it left a massive trail of destruction. Had Mount Saint Helens been a rhyolite volcano, the destruction would have been far worse.

Answer 4

Volcanoes that erupt less viscous lava are less dangerous because they have a lower gas content. High gas content in lava cause more explosive eruptions as is the case of Mt. St. Helens. Higher gas content acting with high viscosity material causes higher presure builup before the eruption, making it so explosive.


A good example of less viscous lava is the lava erupted from the volcanoes in Hawaii. Generally speaking, less viscous lavas are mafic (basaltic), whereas viscous lavas tend to be more felsic (rhyolitic).

Answer 5

Simply put:
The lava is driven by pressure.
A low viscosity lava flows more easily. Allows less pressure build-up, so there's less chance of an explosive event.
With a high viscosity lava pressure builds until the surrounding rock may fracture allowing an explosive release.

Answer 6

Viscousity lava flows at a faster rate then a low viscous flow, thus with a faster flow the lava would spead down the slope further and faster thus making it more dangerous.