Lava Flows

Photograph by J.D. Griggs in 1984

What are lava flows?
Lava flows are streams of melted rock that comes out of the volcano. The rock is not hard like rocks we are used to, but is like a heavy liquid. The melted rock will destroy everything in the way but it moves very slowly. Since it moves so slowly, people can get out of the way. The speed that lava flows at depends on 4 things:
· What kind of lava it is and how thick it is.
· How steep the ground is that it’s traveling on.
· Whether it’s being forced a certain way or can go where it wants.
· How much lava is being produced by the volcano.

A kind of lava called basalt can travel for 20 or more miles. Usually basalt will travel at about 1 kilometer per hour on a gentle slope. This is a little over half a mile per hour. If the ground is steep, the basalt can travel up to 6 miles per hour (10 kilometers per hour). If basalt is on steep ground AND in a channel it can travel up to 18 miles per hour (30 kilometers per hour).

Another kind of lava called andesite only goes about 5 miles and only travels about 1 mile per hour.

Two other kind of lava called dacite and rhyolite often form lava domes since they move so slow. The lava can pile up into domes over 100 feet thick. The domes can spread out but very slowly – about 10 feet per hour.

Everything in the way of a lava flow will be knocked down, buried, or will catch on fire since the lava is so hot. When hot lava touches snow and ice, like on a glacier, it will melt the snow and ice and will lead to mud flows called lahars. If the lava enters water such as a river or lake, the water will boil and can create an explosion. If water goes into a lava tube the same thing can happen.

Thick lava flows, like the ones that build lava domes, can collapse and form pyroclastic flows which move very fast.

People usually don’t die from lava flows because they move so slow and people can leave. Sometimes people are killed or hurt because they go to look at the lava flows and get trapped or they go too close. Sometimes people do die if they are caught in an explosion when hot lava meets water, or they may suffocate because of the toxic gasses created by the lava. If a lava dome collapses and creates a pyroclastic flow, or if a lahar is made when lava touches snow and ice, people can also die.

When something like an earthquake or a hurricane or tornado destroys someone’s home, they can always rebuild, but if lava buries your house, you are out of luck.

Lava buries or surrounds everything.	The heat of lava burns or melts everything.	Lava melts snow and ice to form lahars.	Collapsing lava can form pyroclastic flows.
Photograph by J.D. Griggs on June 6, 1987	Photograph by J. Dvorak in 1983	Photograph courtesy of Magnús Tumi Guðmundsson	Photograph courtesy of Abel Cortes, Colima Volcano Observatory

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