types of lava3

Image demonstrating what happens when there is high water and low silica. Please have someone assist you with this.

Types of Lava
Different types of lavas show behaviors that are similar to our analogies of blowing bubbles in water or a milk shake. If an erupting lava has low viscosity ( like water) and little or no dissolved gases, it simply flows out of the central vent and spreads far and wide over the surface (see low water/low silica figure). If it has high viscosity (like a milk shake) and no dissolved gases, the lava oozes slowly out to form a bulbous dome which hardly moves at all (see low water/high silica figure). In either case, you could stand nearby in relative safety. If the erupting lava has lots of dissolved gases, the gases come out of solution and form bubbles as the lava approaches the surface. If the viscosity of the lava is low, the lava bubbles and froths a great deal right at the surface, tossing out tiny cinders and larger "bombs" of lava that quickly cool and fall back to the ground. This type of eruption (see high water/low silica figure) produces a spectacular "fire fountain" directly over the vent, usually resulting in a cinder cone. Any remaining lava quietly flows away.

Image demonstrating what happens when there is high water and high silica. Please have someone assist you with this.

However, the last combination, lots of dissolved gases and high viscosity, is deadly (see high water/high silica figure). As the lava oozes to the surface, the gases quickly form bubbles that turn the lava into a red-hot froth that explodes out of the ground as a searing, grayish cloud of superheated steam and tiny particles called ash. The ash forms when the walls of the gas bubbles burst into tiny fragments. This type of lava causes explosive eruptions at volcanoes like Vesuvius and Mount St. Helens.